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1. 5 14 5 15 Load Resistor Assembly ne 5 15 5 16 Stepper B nd Uu dou 5 16 5 17 stepper Motor Assembly sere Re DER ERR RR ee 5 18 5 18 Head Carriage Assembly 55 56 ex ba e ean ne Mcr 5 19 APPENDIX I PRINTED CIRCUIT BOARD SCHEMATICS AND ASSEMBLY DRAWINGS sca vectes tent 1 APPENDIX RECOMMENDED SPARE PARTS 5 1 1 2 NaO MNMNNNNNNNNNNN a ww 1 1 1 LI i 1 C 05 05 02 00 02 OONOOAARAN LIST OF ILLUSTRATIONS FIGURES Title of Figure TM848 Disk Drive Mounting TM848 Disk Drive Functional Block FM Recording Magnetization Write Operation Timing Diagram Read Timing DiagraM oec entia fessen raet Circuit Board Q General Control and Data Timing Requirements Radial Ready Installation aar Radial Index Installation 22 2 bad eee
2. AM amp P pc ra frais TNR D7 4 ES IN d WRITE PROTECT SENSOR ASSY Figure 5 14 Write Protect Sensor Assembly Key Parts Installation Using the two original mounting screws attach the Write Protect Sensor Assembly to the chassis Plug P3 into the circuit board Tie wrap the Write Protect wires to the cable harness Checks Verify operation of the Write Protect Sensor Assembly DOOR SWITCH ASSEMBLY Removal Remove P14 from the circuit board Remove the mounting screw from the door switch bracket see Figure 5 15 Cut the tie wraps leading to P14 Lift out the Door Switch Assembly Installation Mount the Door Switch Assembly to the bridge using the original mounting screw Plug P14 into the circuit board Checks Ensure that the door switch operates properly 5 13 INDEX SENSOR ASSEMBLY MOUNTING SCREW E jan Figure 5 15 Door Switch Assembly Key Parts 5 13 1 Removal A Remove the circuit board see Section 5 3 1 B Gently remove the two index L E D s from the Bridge Assembly see Figure 5 16 P1 D F pe Ege UPPER INDEX SENSORS ur m BR T i var 4 SS TIE WRAPS Figure 5 16 Index Sensor Assembly Key Parts Top View G Turn the drive over and remove the mounting screw from the Index Sensor Assembly see Figure
3. DUM See a E Ses 1 14 1 17 3 Program a E VE anes 1 14 1 18 DS and HL Power Save 1 17 1 19 UserSelectable Oplions wiv ado diene ede Eau a oe Ves 1 17 1 19 1 Drve SelectDS1 DSL Lue Ree 1 18 1 19 2 Side Select Options Using Drive Select 1 1 18 1 19 3 In Use From Drive 1 18 1 19 4 In Use From Head 222 TR Karen 1 18 1 19 5 Ready Alternate Output 1 18 1 19 6 Radial Ready ccce ior Sane Seb ee Erit 1 19 1 19 7 Ready s oink hate ir tbt En ies o e x x e des e 1 19 1 19 8 Radia Index dou Db alfo us MEER UE s Ceci 1 19 1 19 9 Index Alternate Output 1 20 1 19 10 In Use Altenate Output Pad ciasssovu a dea chew rad AX RE ENS E LE 1 20 1 19 11 Diskette Lever Lock Latch Option 1 20 1 19 12 DISK Ghahge He 1 20 1 19 13 Two Sided Diskette 1 20 1 19 14 Stepper Power From Drive 1 21 1 19 15 Stepper Power From Head Lo
4. 125 1 10 MOUNTING The DING rss ed qr So Re en 8 1 5 1 10 1 aan WAS Ee yee ad eae hoe INGES 1 6 1 10 2 DUST COVER ue sias es va m ebd Teve NG 1 6 1 10 3 Cooling System 1 6 1 11 Diskette Care Handling and Storage 1 6 1 12 eoa de goi o aniio ache ba dica PO Dre ee AREE 1 7 1 13 Operation of The Drive oa conan sada cused 1 7 1 14 Organization of Jardar ee Mid A x 1 7 1 15 Components of The Drive 1 7 1 15 1 cte ee ates artt NL NA 1 8 1 15 2 Drive Status LOGG qo vest eau ea 1 8 1 15 3 Spindle Drive System SV do ERR e Ea E 1 9 1 15 4 Control adr e E EE aman DERE 1 9 1155 BELE Ga Tee EN NE t 1 9 1 16 Intertace EIectrolllos suos UR od ed x Ra oes acd 1 12 1 16 1 Interface Connector Pin Assignments 13 1 12 1 16 2 Power Connector Pin 5 10 1 12 1 17 Terminated avatar ANTE 1 14 1 17 1 Input Line Terminations From Removable Resistor 1 14 1 17 2 Drive Selettore
5. OPERATING AND SERVICE MANUAL TM848 1 AND TM848 2 DISK DRIVES 48 TRAGKS PER INGH CORPORATION 20320 PRAIRIE STREET CHATSWORTH CA 91311 TELEPHONE 213 993 6644 TWX 910 494 1721 TELEX NO 194794 COPYRIGHT 1982 TANDON CORPORATION The information contained in this document is the property of Tandon Corporation It may not be duplicated in full or part by any person without prior written approval The material in this document is provided for informational purposes and is subject to change by Tandon Corporation TABLE OF CONTENTS Section Page Number Title of Section Number SECTION I INTRODUCTION TO THE TM848 FAMILY OF DISK DRIVES 1 erre 1 1 Purpose OF The gt PIU 1 1 1 2 Physical Description of The 1 1 1 3 Functional Description of The 1 1 1 4 Diskettes NN Ec 1 2 1 5 Mechanical and Electrical 1 2 1 6 POWeOIBedulrementsu sss Ss ad EORR CE DELE VAR buda MUSEOS 1 2 1 7 Interface Circuit 1 2 1 8 Incoming Inspection Checks and 1 2 1 9 Interface CONNECHONG eda sme QUERI
6. For double sided drives select Head 01 and repeat the steps above Note Head 01 should meet the same specification J If either Head 00 or Head 01 does not meet the specifications adjust the index sensor see Section 2 4 2 2 6 Time Scale 50 usec per division Figure 2 5 Index to Data Burst K When both index measurements on double sided drive or the one index measurement on a single sided drive meet the specifications see Section check the index to data burst on Track 76 L On a double sided drive check Heads 01 and OO the upper and lower heads Note If any index measurement does not meet the specification the index sensor must be adjusted see Section 2 4 2 2 4 2 Index Sensor Adjustment A Loosen the index sensors retaining screw located on the underside of the chassis see Figure 2 6 INDEX SENSOR RETAINING SCREW EG oun Figure 2 6 Index Sensor s Retaining Screw and Adjustment 2 7 B Adjust the index sensor with a flat blade screwdriver until the index to data burst occurs 200 microseconds 100 microseconds from the leading edge of the index pulse Tighten the index sensor s retaining screw D Reverify the index to data bursts see Section 2 3 1 2 4 3 Index Pulse Width Check The index pulse width is nonadjustable If the index pulse width is not within specifications replace the Index Sensor Assembly A Set up an oscilloscope as follows Chan
7. Microswitch not connected Misadjusted switch bracket 4 4 RECOMMENDED ACTION Check P11 Replace Activity L D Assembly Replace circuit board See Section 4 2 Check P2 Replace circuit board Replace Sensor Assembly Replace switch Check P14 Realign 5 This section contains the replacement procedures for the TM848 family of disk parts and SECTION V REPLACEMENT PROCEDURES INTRODUCTION assemblies 2 3 10 11 12 13 14 15 16 18 5 1 5 1 1 Drive Belt Drive Motor Circuit Board Cone Assembly Diskette Lever Bridge Assembly Front Panel Activity L E D Load Arm Assembly Track 00 Sensor Assembly Write Protect Sensor Assembly Door Switch Assembly Index Sensor Assembly Diskette Ejector Assembly Load Resistor Assembly Stepper Band Stepper Motor Assembly Head Carriage Assembly DRIVE BELT Removal Turn the drive over so that the spindle is facing upward see Figure 5 1 5 1 5 2 5 2 1 5 2 2 m gt DRIVE BELT SMALL FLANGED SPINDLE PULLEY LARGE SPINDLE PULLEY Figure 5 1 Drive Belt and Spindle Grasp the drive belt and remove it from the pulleys Installation With the shiny side inward loop the new drive belt onto the small flanged spindle pulley While turning the spindle put the drive belt on the large spindle pulley Ch
8. center tap 1 to be selected 3 7 8 6 SSS WRT GATE 4 gt a 4us max U30 Pin 12 Sec A Q output lt 1 550us U30 Pin 13 Sec B Q output U31 Pin3 Trim erase Source Figure 3 5 Trim Erase Diagram 6 Figure 3 6 Side Select Schematic Diagram 12V 4 3 4 OUTPUT CONTROL LINES A INDEX SEGTOR Functional Description The Index signal is provided once eash revolution 166 667 milliseconds nominal to indicate the beginning of a track to the controller The Index line remains in a low true state forthe duration of the index pulse The duration of the Index pulse is nominally 2 0 milliseconds Two index sensors are supplied for use with single or double sided media The leading edge of an Index pulse is always used for timing to ensure diskette interchangeability between drives With standard soft sectored diskette installed the signal at R33 see Figures 3 7 and 3 8 is a high going pulse nominally 2 0 milliseconds in duration every 166 667 milliseconds Circuit Description Light from the Index L E D is usedto drive the index sensor which is applied to the inverting input of U32 This signal is conditioned by U32 then inverted by U33 It is used to drive U26 Then the Respective index pulses are gated by U20 then with drive select by U4 to generate the signal index U26 and the associated support integrated circuits U16 and U20 are co
9. 5 17 5 17 5 17 1 STEPPER MOTOR ASSEMBLY MOUNTING SCREWS 3 PLACES Figure 5 21 Stepper Band Additional Key Parts STEPPER MOTOR ASSEMBLY Removal It is suggested that the drive be returned to an authorized Tandon repair center when removing the Stepper Motor Assembly A B 5 17 2 Remove the circuit board see Section 5 3 1 Remove the stepper band see Section 5 16 1 Remove the three mounting screws that attach the Stepper Motor Assembly to the chassis see Figure 5 22 Remove plug connectors P4 and P5 from the circuit board Cut the tie wraps that connect the stepper motor wires to the load resistors Lift out the Stepper Motor Assembly Note Be careful not to damage the stepper band Installation Place the Stepper Motor Assembly into the drive s chassis Usingthe original three mounting screws attach the Stepper Motor Assembly to the chassis STEPPER MOTOR ASSEMBLY MOUNTING SCREWS 3 PLACES Figure 5 22 Stepper Motor Assembly Key Parts C Replace the stepper band see Section 5 16 2 D Replace the circuit board see Section 5 3 2 5 17 3 Checks A Align the E lobes on the drive see Section II 5 18 HEAD CARRIAGE ASSEMBLY 5 18 1 Removal It is suggested that the drive be returned to an authorized Tandon repair center when removing the Head Carriage Assembly Remove the Stepper Motor Assembly see Section 5 17 1 Remo
10. 5 7 MOUNTING SCREWS 2 EA SIDE BRIDGE ASSY INDEX L E D s 2 4 5 LEVER SHAFT Bridge EL Key Parts 2 EA SIDE NE 5 7 BEZEL 5 7 1 Removal A Remove the diskette lever see Section 5 5 B Remove the four bezel mounting screws two on each side that attach the bezel to the chassis see Figure 5 10 BEZEL A MOUNTING SCREWS 2 HIE D 77 4 DISKETTE LEVER E x mme d n 7 xL ER ge I BEZEL MOUNTING SCREWS 2 Figure 5 10 Bezel and Related Parts C Lift off the bezel being careful that the Activity L E D comes out of its mounting with no binding 5 8 5 7 2 5 8 5 8 1 5 8 2 gt 5 8 3 gt Installation Put the bezel on the drive ensuring that the Activity L E D goes into its holder Install the four bezel mounting screws that attach the bezel to the chassis Checks Ensure that the Activity L E D goes on when required Ensure that the diskette lever clamps the cone and loads the head AGTIVITY L E D Removal Remove the bezel see Section 5 7 1 Remove the brackets that hold the bundle of wires going to P11 from the chassis see Figure 5 11 TIE BRACKETS 2 FAR SIDE ACTIVITY LIGHT WIRES BRACKET 1 NEAR SIDE ACTIVITY L E D INSIDE Figure 5 11 Activity L E D Key Parts Remove the Activity L E D a
11. Bris ki AX Figure 2 8 Track OO Sensor RETAINING SCREWS L Push the sensor toward the back of the drive and slowly push it forward until the signal on the oscilloscope just goes low true M Tighten the retaining screws and repeat Steps E through I N Verify the adjustment 2 6 AMPLITUDE CHECK The amplitude test checks the necessary read channel amplifier differential output voltage A Restore to Track 00 Insert work diskette and write 2F all ones pattern on the lower head 2 9 C Connect an oscilloscope to Test Points 4 and 5 using Test Point 1 as a ground D Set up an oscilloscope as follows Channel A Test Point 4 1 volt per division Channel B Test Point 5 1 volt per division Both Channels coupled Channels and added Channel B inverted Time Base 50 milliseconds per division synchronize internally on Channel A or B Trigger Automatic E The minimum amplitude displayed on the scope should be no less than three 3 volts peak to peak at any point F Reverify the measurement with another work diskette G Check the upper and lower head if applicable H If the amplitude is less than the specification inspect the heads to ensure they are not contaminated l Clean the heads with a cleaning diskette if they are contaminated J Replace the circuit board if cleaning does not improve the amplitude K If replacing the circuit board does not correct the
12. Checks Ensure that the diskette lever is perpendicular to the drive when the diskette is clamped See Figure 5 7 for the adjustment Ensure that the diskette lever is parallel to the drive when the diskette is unclampled See Figure 5 7 for the adjustment BRIDGE ASSEMBLY Removal Remove the circuit board see Section 5 3 1 Remove the diskette lever see Section 5 5 1 Remove the four bridge mounting screws that attach the Bridge Assembly to the chassis see Figur 5 8 BEZEL y MOUNTING SCREWS 2 BEZEL mes E Figure 5 7 Ne SUE MOUNTNG SCREWS 2 Diskette Lever Adjustment DISKETTE LEVER BRIDGE MOUNTING SCREWS 2 BOTH SIDES BEZEL SCREWS 2 BOTH SIDES Figure 5 8 Bridge Assembly Key Parts D Carefully pull out the two index D s in the Bridge Assembly E Carefully lift out the Bridge Assembly toward the back of the drive The shaft must clear the bezel 5 6 2 Installation A Insert the shaft into the bezel and lay the Bridge Assembly in place B Instail and tighten the four bridge mounting screws that attach the Bridge Assembly to the chassis C Install the two index L E D s into the Bridge Assembly D Install the diskette lever see Section 5 5 2 E Install the circuit board see Section 5 3 2 5 6 3 Checks A Ensure that the diskette lever clamps the cone and loads the head see Figure 5 9
13. F Remove the ejector 5 14 2 Installation A Insert the ejector B Engage the spring attached to the rear of the ejector C Insert the Bridge Assembly approximately two inches taking care to put the L E D sintheir respective sockets D Reinstall the original four screws that hold the Bridge Assembly E Push on the lever Reinstall the retaining SEG Insert the small plug in the door lever F Reinstall the circuit board see Section 5 3 1 5143 Checks A Insert a work diskette into the drive B Ensure that the diskette stays in prior to being closed C Close and open the diskette lever D The diskette should eject E If not see Section 5 4 5 15 LOAD RESISTOR ASSEMBLY 5 15 1 Removal A Remove P5 from the circuit board B Remove the circuit board see Section 5 3 1 C Remove the two mounting screws that attach the Load Resistor Assembly to the chassis D Unsolder the wires to the load resistors see Figure 5 19 E Mark or identify these wires so that they can be put back in the same location MOUNTING SCREWS 2 LOAD RESISTOR ASSEMBLY SOLDER JOINT 4 PLAGES Figure 5 19 Load Resistor Assembly and Key Parts 5 15 2 Installation A Solder the wires back in the same place at which they were originally B Mount the Load Resistor Assembly onto the chassis using the two original mounting screws C Install the circuit board see Section 5 3 2 D Plug P5 into the circuit board 5 15 3 Checks
14. TRACK 00 SENSOR ASSEMBLY Removal Remove P2 from the circuit board Cut the tie wraps that hold the cable harness and remove the P2 wires see Figure 5 13 TRACK 00 IT SENSOR ASSEMBLY BT I e mes Figure 5 13 Track 00 Sensor Assembly Key Parts MOUNTING DW aol 6 SCREWS ga 22 IL zi BRACKET LM esa 14 TIE WRAPS C Remove the P2 wires from the bracket attached to the chassis D Remove the two mounting screws that hold down the Track 00 Sensor Assembly E Lift off the Track 00 Sensor Assembly 5 10 2 Installation A Using the two original mounting screws install the Track 00 Sensor Assembly B Loop the P2 wires from the Track 00 Sensor Assembly through the bracket attached to the chassis C Using tie wraps cable harness the P2 wires and the other wires together D Plug P2 into the circuit board 5 10 3 Checks A Adjust the Track 00 sensor see Section Il 5 11 WRITE PROTECT SENSOR ASSEMBLY 5 11 1 Removal A Remove P3 from the circuit board B Remove the two mounting screws that attach the Write Protect Sensor Assembly to the chassis see Figure 5 14 C Cutthetie wrapsthat hold the wirestothe cable harness and lift out the Write Protect Sensor Assembly 5 11 2 A 5 12 3 MOUNTING SCREWS 2 P3 EERIE ERANO VERE EEDE 195 100000 R Le
15. A Enable the drive through the interface logic B Step the drive to Track OO C Step the drive to Track 76 D Do the C E alignment verification procedure see Section ll 5 16 STEPPER BAND 5 16 1 Removal It is suggested that the drive be returned to an authorized Tandon repair center when removing the stepper band A Remove the circuit board see Section 5 3 1 B Lift off the stepper band from the spring tensioner see Figure 5 20 SCREW ATTACHES BAND TO CARRIAGE ASSEMBLY SPRING TENSIONER STEPPER BAND SPRING TENSIONER Figure 5 20 Stepper Band Key Parts C Remove the screw that attaches the front of the stepper band to the Head Carriage Assembly D Remove the mounting screw that attaches the stepper band to the stepper pulley E Lift out the stepper band 5 16 2 Installation A Screw the front of the stepper band into the Head Carriage Assembly see Figure 5 21 B Loop the stepper band around the stepper pulley C Attach the rear of the band to the spring tensioner D Attach the stepper band to the stepper pulley loosely with the mounting screw E Move the Head Carriage Assembly back and fourth at least five times F Visually inspect the stepper band to ensure that it is centered on the stepper pulley G Tighten the mounting screw that attaches the stepper pulley to the stepper band H Install the circuit board see Section 5 3 2 5 16 3 Checks A Check C E alignment see Section ll
16. IT dA TYP APL ULN 2074 B 2 TYP4PLYPINS 4 5 12 13 GND d CRG I 24V IN 1 m 24V 333K I 3 gt gt 3 STEP MOTOR 2 424V CRI L 4 24 29 oat 1 2 0 seza 21 188 S 24V mm dd 5 CR5 3 36 25 6 4 CRO DA 5 lt 42 7 iz A I MEG RIS CHASSIS B GROUND cu MODNING 0 00 La RESISTOR LOCATED IM SAME RESISTOR PACK mises cames Memes ne SIGNATURES DATE paa CLARUM A iren UE landon MRE PROC MRR ng OR MOLINA WRITTEN PERCUSSION CORPORATION A UNLESS NEXT ASSY FIRST USE APPLICATION a MODEL DISKETTE 262 ELECTRONICS MATL z CODE IDENT NO ID NO ETT rest pene nor some 1 OF 2 1 8 7 6 5 4 3 2 1 mv ememenon os es E SEE SHEET 1 TT H2VZ SPINDLE 2 VI D SW 4 ual MS 97OL SPEED CONTROL SIP PACK R22 MSEL R143 12v2 M b Pink 150 u 25 gt BLU 220 lt RUN 2v2 5 WHEN Hi 47K p I QV a LM290146 5 pur I 2 5 55 GRY 220 14 2v2 oA SWITCH OPEN POR 2 Bo MITRON HSA Riaz C DISKETTE A
17. RSE Yo HEAD LOAD Jue m hever we Are Ble 5 Riaz POR Figure 3 3 Select Lines Schematic Diagram A select line must remain stable in the true low state until after a Step or Read Write command has been executed The drive select address 1 4 is determined by shorting plugs on the circuit board Select lines 1 through 4 provide a means of daisy chaining a maximum of four drives to a controller Only one line can be true low at a time An undefined operation might result if two or more units are assigned the same address or if two or more select lines are in the true low state simultaneously Circuit Description An 150 ohm resistor holds the output of the appropriate Select line high false until the line is driven low true Then the Select signal is gated through U1 and U5 to derive the signal DRSEL DRSEL is used to gate all I O Port ensuring that only one drive s data is present on the interface at a time Writing and stepping are also gated by the signal DRSEL This signal is inverted by U13 then buffered by U15 to drive the Activity L E D which is located on the front panel Option Z is factory installed It should be installed for the Activity L E D to operate with Drive Select B MOTOR ON Drive Motor Enable 3 2 TABLE 3 1 DRIVE INTERFACE LINES AND PIN CONNECTORS Ground Pin Number Signal 1 2 Write Current Switch 3 4 Motor Off Control 1 5 6 Motor Off Control 2 7 8 Motor Off
18. and double sided drives Apply power to the drive Note The Track 38 radius is 2 8207 0020 Other track locations are computed based upon 48TPI Select the drive at the interface Insert the alignment diskette into the drive Select Head OO the lower head Seek to and observe Track 38 for Cats Eye alignment of the lower head Adjust the oscilloscope to observe a Cats Eye pattern see Figure 2 3 Equal amplitude Lobes shown at 100 percent on Track 38 Time Scale 20 ms Figure 2 3 Cats Eye Pattern 2 3 H Verify that the smaller of the two Cats Eye lobes is not less than 75 percent in amplitude of the other one The calculation is amp of smaller lobe amp of larger lobe X 100 l Step the drive to Track OO then step it back to Track 38 J Reverify the Cats Eye pattern K Step the drive to Track 76 then step it back to Track 38 L Reverify the Cats Eye pattern M On double headed drives select the upper head Head O1 and repeat Steps F through L N If any of the checks listed above does not meet the conditions stated in Step H the head carriage must be adjusted HEAD CARRIAGE ADJUSTMENT A Turn the two position retaining screws that straddle the nylon adjustment cam located beneath the drive until the cam can be moved see Figure 2 4 POSITION RETAINING SCREWS 2 9 b ADJUSTMENT CAM Figure 2 4 Head Module Retaining and
19. Cone Assembly down 90 degrees so that it points toward the bottom of the unit 5 4 CONE BRAGKET SCREW CONE ALIGNMENT ARM E RING amp WASHER WAVE WASHER DISKETTE LEVER E Pru EI LEN n Tea I CONE ASSY Figure 5 4 Cone Assembly Key Parts D Latch the diskette lever E Insert the screw that attaches the cone bracket to the cone alignment arm see Figure 5 5 lum FLAT WASHER wj 7 WAVE WASHER lt BRACKET ne d END FLAT WASHER 2 DL CONE ASSEMBLY Figure 5 5 Cone Assembly Parts 5 4 3 Checks A Ensure that the Cone Assembly turns freely B If not reverify that the Cone Assembly has been installed correctly C Insert a diskette D Ensure that the diskette is clamped properly by the cone 5 5 5 5 5 5 1 DISKETTE LEVER Removal A Pry off the cover that hides the diskette lever s retaining screw see Figure 5 6 5 5 2 gt 5 5 3 5 6 5 6 1 MOUNTING SCREW DISKETTE LEVER Figure 5 6 Diskette Lever Key Parts Remove the diskette lever s retaining screw Carefully remove the diskette lever Installation Put the diskette lever on the shaft Put a drop of Locktite Number 234 on the threads of the diskette lever s screw Install and tighten the diskette lever s screw Put the cover back on the diskette lever
20. Stepper Motor Assembly Check options DS and HL for the particular application SECTION 4 3 4 4 4 5 CONDITION WILL NOT WRITE WILL NOT READ AGTIVITY L E D INOPERATIVE POSSIBLE CAUSE Interface not enabled Heads or write protect switch not connected Write protect switch misadjusted Defective write logic Defective heads Misadjusted platen load arm Interface incorrect Alignment off Defective read electronics Defective heads Platen load arm misadjusted Interface not enabled RECOMMENDED ACTION Verify write enable select and write data interface lines Check Connectors P3 P8 and P9 Check write protect switch operation Replace circuit board Replace Head Carriage Assembly Adjust platen load arm Verify select is true and write enable is false Verify C E lobes index burst and Track OO sensor adjustment Replace circuit board Replace Head Carriage Assembly Adiust platen load arm Verify interface select and jumper configuration SECTION 4 5 4 6 4 7 CONDITION AGTIVITY L E D INOPERATIVE NO TRACK 00 SENSOR INDICATION DRIVE MOTOR WILL NOT START WHEN DOOR LATCHED POSSIBLE CAUSE Activity L E D not connected Activity L E D defective Activity L E D driver defective Defective seek Track OO sensor not connected Defective logic Defective Track 00 sensor Defective microswitch
21. U21 9 0 0 1 1 0 U21 8 1 0 0 1 1 U21 8 1 1 0 0 1 U21 5 0 0 1 1 0 U21 5 1 1 021 6 1 1 1 021 6 1 1 1 The step pulses come in at Pin 36 of the interface connector They are buffered by 022 and gated at U14 by the unit select and the Not Write signal The step pulses then go to the C inputs of the two flip flops at U21 The direction of the step hence the selection of the flip flop to be toggled is done by the two exclusive OR gates of U9 These gates are controlled by the step direction line and by the state of the two flip flop outputs The POR Power On Reset signal resets the two flip flops to Phase after a Power On The output of the twoflipflops drivesthe stepper motorthrough the drivers of U39 U40 and U12 The diodes CR2 9 are for voltage spike elimination The current through the stepper motor coils is reversed sequentially one at a time D WRT GATE Functional Description When the Write Gate signal is true low the write electronics are prepared for writing data read electronics disabled This signal turns on the write current in the read write head Data is written under control of the Write Data input line It is necessary for the Write Gate interface line to go low before the first Write Data pulse However the separation between the leading edge of Write Gate and the first significant Write Data pulse should not be less than two microseconds and not greater than four microseconds The same restric
22. Write When Write Protected NP X Head Side Select Options 51 53 52 Spindle Motor Control Options M1 M4 M1 M3 M2 M4 Motor Control Select MC1 MC4 MC1 1 19 1 Drive Select DS1 DS4 This option allows the user to daisy chain up to four drives and to enable one drive at at time Drive select is implemented by shorting one of the four connections using a shorting plug The drive comes equipped from the factory with DS1 installed All outputs are gated with drive select as set up at the factory 1 19 2 Side Select Options Using Drive Select 1 4 This option allows the user to select the head to be used with drive select Side Select options are implemented by removing the shorting plug from the DS1 DS4 option pads installing Pins 1B 4B and connecting the shorting plug to the desired 1B 4B pins 52 should be etch cut and S3 installed see Section 1 18 1 19 3 Use From Drive Select 2 This option allows the user to enable the activity L E D when the drive is selected In Use From Drive Select is factory installed 1 19 4 Use From Head Load Y This option allows the user to use the head load line to enable the Activity L E D In Use From Head Load is implemented by punching out Option Z between Pins 1 and 16 of U3 A jumper must be installed at location Y 1 19 5 Ready Alternate Output Pad This low going signal is derived by gating the internal ready and drive select to give the controller a true low ready sta
23. amplitude replace the Head Carriage Assembly 2 7 AZIMUTH CHECK Azimuth is the angle of the heads with respect to the track at the point of the read write gap Azimuth is measured in minutes one minute 1 60 degree A Set up an oscilloscope as follows Channel A Test Point 2 100 mV per division Channel B Test Point 3 100 mV per division Ground Test Point 1 Both Channels A C coupled Channels A and B added Channel B inverted Time Base 1 millisecond or as required to display the pulse groups Trigger Leading edge of appropriate test point see Section 2 Item Number 1 B Insert an alignment diskette C Step the drive to Track 76 D Observe the following pattern Figure 2 9 depicts an optimum head alignment of zero minutes of azimuth error This means that the Head Carriage Assembly is perpendicular to the track being read Track 76 Bursts 1 and 4 are of equal amplitude Bursts 2 and 3 are of equal amplitude Note Measure the azimuth burst Ensure that Burst 1 is less than or equal to Burst 2 and that Burst 4 is less than or equal to Burst 3 1 2 3 4 Figure 2 9 Optimum Head Azimuth Alignment E Figure 2 10 depicts an azimuth of exactly minus 9 12 or 18 minutes depending upon the manufacturer of the diskette used This is the lower limit of allowable azimuth error Bursts 1 and 2 are of equal amplitude If this signal is observed the Cats Eye alignment should be checked prior to any correcti
24. ancon WILTSHIRE 2 Tandon ES re RESISTOR LOCATED IN RESISTOR PACK 8 7 2 6 5 4 NEXT ASSY APPLICATION FIRST USE 2 1 O prsenerton fore ow ers SH I Fe MODEL 848 DISKETTE FET DRIVE ELECTRONICS J em pe 2 o 5 1 8 7 6 5 4 3 2 1 nv DESCRIPTION parE APPR SEE SMN Tee 822 wn IKI R27 C M EDI cgo V os Z R22 t b IK 1 pin 15 56012 R25 1 7 5 nav O LuF C27 Pr 5 1 1 READ ELECTRONICS B B THE INFORMATION CONTAINED HEREON 18 THE PROPERTY AMDON HAGNETICS MO PORTION OF THIS HATA SMALL DE RELEASED ee POENGET A ROM TAGER madi rca PERMISSION NEXT ASSY FIRST USE DI 2 0022 ao0 SCALE 2 NOT SCALE HET 2 OF APPLICATION 8 7 I 3 6 5 4 3 2 1 6 5 4 PR N alo SHI gt m SET 9 H 02 zar 5 CLR POR 5 WRITE L 7410 DR SEL 2 2 POWER SH 5 L2H oy mme AW 5 CRI T gt 4 C40 1 O uf GIS 1 3 5 4 7K 5 STPEN 75472 5V ZAV D 24V RAB CR2 35 ae 257 IN 4003 VE
25. cable be ribbon cable with characteristic impedance of 100 ohms Interface connector pin assignments are given in Table 3 1 3 3 INPUT CONTROL LINES 051 054 Select Lines Functional Description The select lines see Figure 3 3 provide means of selecting and deselecting drive These four lines 051 through DS4 select one of the four drives attached to the controller When the signal logic level is true low the drive electronics are activated and the drive is conditioned to respond to Step or Read Write commands When the logic level is false high the input control lines and output status lines are disabled 5V tSv POR R4 pg 051 Suds POR 052 1504 ke 250 504 095 STPEN ps5 c V 554 gt ago 9 13 HEAD aD SOLE SV 2 SOLENOID P SIDE 1 30 4 5 SIDE 4 5 5022 ES gt gt DR 5R 54 EEE iSo 2 02 504 424500 950 101 gt jos 13 V l 2 SV D 1 ACTIVITY f is ra i Y LED o o 2e 4 Moen 5 FK a HERD LOAD PRIO XOS 4 RERB 85 00 50 oP wat as LEVER I Il iN USE gt o P0 o0 929 174 iss 278462 SOLENOID OL GE ale 002 BD H i
26. four on the bottom of the housing see Figure 1 1 The two on each side are tapped for 8 32 screws The four mounting holes on the bottom require 8 32 thread forming screws Optional straps are available to permit attaching two drives together for installation in standard width drive openings 1 5 an il gt 6 32 THD m THRU 4 PL le e 19 2 EA SIDE Ep l L Cr Ln 149 DIA TOP X 156 DIA BOTTOM X 430 DP 4 PL s 11 lal NOTES DIMENSIONS GIVEN IN INCHES Figure 1 1 TM848 Disk Drive Mounting Configuration 1 10 1 Hardware The drive is manufactured with certain critical internal alignments that must be maintained Hence it is important that the mounting hardware does not introduce significant stress on the drive A three part mounting scheme is recommended Any mounting scheme in which the drive is part of the structural integrity of the enclosure may cause equipment operating problems and should be avoided In addition the mounting scheme should allow for adjustable brackets or incorporate resilient members to accommodate tolerences 1 10 2 Dust Cover The design of an enclosure should incorporate a means to prevent contamination from loose items e g dust lint and paper since the drive does not have a dust cover 1 10 3 Cooling System Requirements Heat dissipation from a
27. from the factory HL is installed but will remove power from the stepper motor when the drive is deselected There should be 20 millisecond wait after Drive Select command is given in order to allow the step motor electronics to settle The stepper power from drive select DS option allows the user to remove D C power from the stepper motor using drive select which results in lower stand by current consumption This option is implemented by installing DS and cutting HL 1 19 USER SELECTABLE OPTIONS The description of user selectable options should be used in conjunction with the following list of options that are available for model numbers TM848 1 and TM848 2 see Table 1 5 TABLE 1 5 OPTIONS AS SHIPPED TRACE Shunt Pin Not OPTION DESIGNATOR Locations Installed Installed Drive Select DS1 DS4 DS1 Side Select Options using Drive Select 1B 4B X In Use Drive Select Z U3 1 16 X In Use Head Load Y X Ready Alternate Output Pad R U3 7 10 X Radial Ready RR X Ready Modified RM X Radial Index RI X Index Alternate Output Pad U3 6 11 X In Use Alternate Output Pad D X Diskette Lever Lock Latch Option DL X Disk Change DC X Two Sided Diskette Installed 25 X Stepper Power from Drive Select DS X Stepper Power from Head Load Line HL U3 2 15 X Head Load Alternate Output Pad C X Radial Head Load Signal A U3 3 14 X Radial Head Load Signal B U3 4 13 X Radial Head Load Signal X U3 5 12 X Inhibit Write When Write Protected WP X Allow
28. interface line The index circuitry consists of an index E D an index phototransistor and a pulse shaping network As the index hole in the disk passes an index E D phototransistor combination light from the E D strikes the index phototransistor causing it to conduct The signal from the index phototransistor is passed on to the pulse shaping network which produces a pulse for each hole detected This pulse is presented to the user on the index pulse interface line 1 15 2 Drive Status Logic There are five drive status logic lines Write Protect Track O0 Sensor Two Sided Ready and Disk Change A Write Protect A write protect signal is provided to the user s system via the write protect interface line The write protect circuitry consists of a write protect sensor and circuitry that routes the signal that is produced When a write protected diskette is inserted in the drive the sensor is activated and the logic disables the write electronics and supplies the status signal to the interface B Track 00 Sensor The level on the Track OO interface line is a function of the position of the head assembly When the head is positioned at Track 00 and the stepper motor is at the home position a true low level signal is generated at the interface C Two Sided Disk This signal is low true when the drive is selected and has detected the presence ofthe Index Two hole in the diskette currently installed D Ready This
29. power to the drive C Select the drive and ensure that the Activity L E D located on the bezel illuminates D Insert a work diskette and write verify from Track OO to Track 76 Ensure that there are no errors E Inserta diskette written previously on another drive Read this diskette and ensure that there are no data errors If excessive errors occur check the diskette on the drive on which it was written If the drive passes all the checks listed above it is operational If not review Section 1 9 INTERFACE CONNECTIONS Signal connections for the drive are made via a user supplied 50 pin flat ribbon connector 3M Scotchflex 3415 This connector mates directly with the circuit board connector at the rear of the drive The D C power connector is a six pin connector Amp Mate N Lok Part Number 1 480270 0 which mates with the connector at the rear of the drive The signal connector harness should be ofthe flat ribbon ortwisted pairtype have a maximum length of ten feet and have a 22 to 28 gauge conductor compatible with the connector that is to be used Power connections should be made with 18 AWG cable minimum 1 10 MOUNTING THE DRIVE The drive has been designed to mount in any plane i e upright horizontal or vertical The only restriction is that the printed circuit board side of the chassis must be uppermost when the drive is mounted horizontally Eight holes are provided for mounting two on each side and
30. respectively Head load is accomplished by connecting both option pads C located near interface connector P13 1 19 17 Radial Head Load Signal Options X By selection of the appropriate combination of the A B or X jumper the user can use either Drive Select or Head Load to activate the Activity L E D and Lever Lock Solenoid option see Figure 1 10 5V SV EER 150 150 pee xs R4 285 RO 55 POR IBO ps2 Sp Soa 052 25 389 6 ie 504 22 STPEN ps 555 o gt 9 yu ota ru 55a 2 gt ago 9 200 9502 HEAD 58 g jor 4 FE SV a Jur SIDE 1 a SO BEBE A gt b 42 gt Lei 9 2 L taa DRSEL r 1500 4202 NS DORSEN URS R98 zi CAD jus O 100 a T SW 14 DN Y NT E Dern SS J DEE t 24206 uenp LOAD i XOS 2 8 JOS 24 pP FERS RD gt 4 0 TE age 025 WDLOD 275407 SOLENOID iN OSE 602 0 1 900 pio ct Leases usa Lae DORSEY t Dk HEAD LOAD ed hver LATCH Piz Figure 1 10 Radial Head Load Signal 1 19 18 Inhibit Write When Write Protected WP This option is used to lock out the write gate when a write protected diskette is installed Inhibit Write When Writ
31. signal is true when Drive Select is low true if the spindle drive is up to speed and the drive is ready to read and write E Disk Change This signal is true when Drive Select is low true if the diskette lever has been moved to the open position after the previous drive select went false 1 8 1 15 3 Spindle Drive System The spindle drive system consists of a spindle assembly driven through a drive belt by a brushless D C motor tachometer The servo electronics required for speed control are located on the printed circuit board The control circuitry contains an interface control line When the drive motor control interface line is false high the drive motor is allowed to come up to speed READY INDEX SENSOR CONTROL INDEX 3 U LOGIC DISK CHANGE TWO SIDED D C STEPPER C 4 WRITE MOTOR H WRITE PROTECT TRAC OG 4 GE SENSOR L E D INDEX DETECTORS y SIDE SELECT WRITE HEAD CARRIAGE AND STEPPER BAND ASSEMBLY PROTECT DETECTOR DRIVE SELECT SPINDLE VN Ion MOTOR CONTROL CONTROL WRITE 2 WRITE WRITE DATA LOGIC CURRENT SWITCH READ READ DATA LOGIC DIRECTION STEPPER MOTOR CONTROL Figure 1 2 TM848 Disk Drive Functional Block Diagram 1 15 4 Positioner Control The head positioning system uses bipolar driven motor drive which changes one phase for each track
32. single drive is normally 30 watts 102 Btu Hr under high line conditions When the drive is mounted so that the components have access to the free flow of air normal convection cooling allows operation over the specified temperature range Whenthe drive is mounted ina confined environment air flow must be provided to maintain specified air temperatures in the vicinity of the motors the circuit board and the diskette 1 11 DISKETTE CARE HANDLING AND STORAGE It is important that the diskette be cared for handled and stored properly so that the integrity of the recorded data is maintained A damaged or contaminated diskette can impair or prevent recovery of data and can result in damage to the read write heads of the drive The following list contains information on how the diskette can be cared for handled and stored 1 Keep the diskette away from magnetic fields 2 Do not touch the precision surface of the diskette with fingers 3 Insert the diskette carefully into the drive until the backstop is encountered 4 Do not bend or fold the diskette 5 Put the diskette into its jacket when it is not in use 6 Store the diskette at temperatures between 10 C and 52 C or 50 F and 125 F 1 12 WRITE PROTECT The drive 15 equipped with Write Protect Sensor Assembly This sensor operates in conjunction with diskette that has slot cut in the protective jacket When the slot is uncovered the diskette is write protected The
33. with the read write circuitry The signal WR PROT is inverted by U33 and gated with DR SEL to generate the Write Protect signal F READ DATA Functional Description The Read Data interface line transmits the read data to the controller when the drive is selected It provides a pulse for each flux transition recorded on the media The Read Data output line goes true low for a duration of 200 nanoseconds for each flux change recorded The leading edge of the low going read data output pulse represents the true positions of the flux transitions on the diskette surface 3 rd ROT PROTECT p 159 LED Figure 3 10 Write Protect Schematic Diagram Test Points 2 and see Figure 3 11 are provided observe the differential output of the first stage of Read signal preamplification Test Points 4 and 5 are provided to observe the differential output of the second stage amplifier and differentiated Read signal Test Point 9 is the output of thesingle shot used in the Read section nominally 200 nanoseconds for each flux transition detected Test Point 1 is signal ground Circuit Description The read signal comes from the selected head on the drive It is gated to the preamplifier U7 by the Write signal to U25 which forward biases diodes CR14 and CR15 Then the Read signal passes through a linear bandpass filter The Read signal is then input to U2 the differentiator The output of U2 goes through
34. 5 17 D Remove the two brackets that attach the Index Sensor Assembly s wires to the chassis see Figure 5 16 E Cut the tie wraps along the cable harness see Figure 5 16 F Lift out the Index Sensor Assembly P1 5 13 2 m 5 13 3 5 14 5 14 1 TIE BRACKETS 2 FAR SIDE TIE BRACKET 1 NEAR SIDE LOWER INDEX SENSOR ASSEMBLY MOUNTING SCREW Figure 5 17 Index Sensor Assembly Key Parts Bottom View Installation Put the Index Sensor Assembly into the drive Loop the wires to the cable harness and chassis Insert the two L E D index sensors into their sockets Using the original mounting screw attach the index L E D to the drive s chassis Cable harness the bundle of wires including the Index Sensor Assembly s wires Reinstall the circuit board see Section 5 3 2 Checks Check the index to data adjustment see Section 1 DISKETTE EJECTOR ASSEMBLY Removal Remove the circuit board see Section 5 3 1 Remove the door lock lever see Figure 5 6 Locate and remove the four screws two on each side that hold the Bridge Assembly see Figure 5 7 EJECTOR TRIGGER HOLD DOWN SCREW PIVOT BAR EJECTOR SPRING TRIGGER ASSEMBLY Figure 5 18 Diskette Ejector Assembly Key Parts D Lift up the Bridge Assembly approximately two inches taking care not to pull the L E D s from their sockets E Release the spring attached to the rear of the ejector
35. Assembly Key Parts Cone Assembly Parts Diskette Lever Key Parts Diskette Lever Adjustmierit olco ee ex ree pee ds Bridge Assembly Key Parts Bridge Assembly Additional Key Parts S 9 4 8 P 3 V d oU NJ 8 eer 4 85 4 9 9 94 ow V W n w Figure Number h b h r FIGURES Page Title of Figure Number B Zel and Related Parts odore eee a EIN E Rx PRA 5 8 A tivity LE D Kev Parts RT PC ees 5 9 Load Arm Assembly Key 225 22 22425 4 12 5 R3 a ERI EAR EA 5 10 Track 00 Sensor Assembly Key 5 11 Write Protect Sensor Assembly Key 5 12 Door Switch Assembly Key 5 13 Index Sensor Assembly Key Parts Top 5 13 Index Sensor Assembly Key Parts Bottom 5 14 Diskette Ejector Assembly Key 5 15 Load Resistor Assembly and Key Parts 5 16 Stepper Band Key Parts usce irte e d outer to c EA KC RR 5 17 Stepper Band Additional Key Parts 5 18
36. Cam Screws B Observe the Cats Eye pattern from the head that is farthest out of alignment Using flat blade screwdriver turn the adjustment cam until one Cats Eye lobe is within 75 percent of the amplitude of the other lobe Note Check the upper and lower heads on double sided drives see Section 2 2 1 through L on upper head D Tighten the two positioner retaining screws see Figure 2 4 2 5 E Reverify the Cats Eye alignment see Section 2 2 1 2 4 INDEX SENSOR CHECKS AND ADJUSTMENTS The index adjustment changes the time period from the index pulse to the start of the data The adjustment should be checked after the drive has been aligned see Section 2 1 1 or when diskette interchange errors are suspected 2 4 1 Index to Data Burst Check A Apply power to the drive B Select the drive Check the spindle speed of the drive see Section 2 1 D Set up an oscilloscope as follows Trigger Single sided drives trigger on right lead of R33 closest to DS2 negative edge double sided drives trigger on Test Point 12 negative edge Read Differentially A plus B B inverted Channel A Test Point 2 Channel B Test Point 3 Time Base 50 microseconds per division E Insert an alignment diskette F Seek to Track 1 G Select Head 00 the lower head H Ensure that the index to data burst occurs at 200 microseconds 100 microseconds from the leading edge of the index pulse see Figure 2 5
37. Control 3 9 10 Two Sided Strappable Model TM848 2 only 11 12 Disk Change Strappable 13 14 Side Select Model TM848 2 only 15 16 Activity Indicator Strappable 17 18 Head Load Line 19 20 Index 21 22 Ready 23 24 Motor Off Control 4 25 26 Drive Select 1 Side Select Option TM848 2 only 27 28 Drive Select 2 Side Select Option TM848 2 only 29 30 Drive Select 3 Side Select Option TM848 2 only 31 32 Drive Select 4 Side Select Option TM848 2 only 33 34 Direction Select Side Select Option TM848 2 only 35 36 Step 37 38 Write Data 39 40 Write Gate 41 42 Track 00 43 44 Write Protect 45 46 Read Data 47 48 Alternate I O 49 50 Alternate I O 3 3 Functional Description The 848 has a D brushless motor that can be enabled in three ways 1 By using the four radial Motor Control lines MC1 through MC4 2 By the Head Load line using shorting plug M4 Using this line enables all drives Motor On lines 3 By Drive Select using shorting plug M3 The Motor Control lines MC1 through MC4 are true low signals that turn the motor off Shorting plug M2 must be installed for these control lines to operate When a Motor Control line is false high the drive motor accelerates to its operational speed in less then 500 milliseconds This keeps the spindle rotating at a constant speed of 360 RPM When the Motor Control line is true low the motor coasts to a stop When using Head Load to enable the drive motor M4 must be
38. D TRACK SENSOR Figure 3 9 Track 00 Schematic Diagram Circuit Description When the read write carriage is restored to Track OO a tab on the carriage blocks light from the Track 00 L E D turning off the Track 00 sensor transistor This enables the inverting input of U32 a quad comparator causing U32 Pin 13 to go high This signal is gated with Phase 0 of the step circuit and with drive select to generate the signal TRK 00 The signal at Test Point 10 should go high between Tracks 2 and 3 as the carriage is being moved toward TRK OO E WRITE PROTECT Functional Description When the drive is selected and the diskette is write protected the WRITE PROTECT line s true low The write electronics are internally disabled when the diskette is write protected see Option Listing for exceptions When the signal on the WRITE PROTECT line is false high the write electronics are enabled and the write operation can be performed It is recommended that the controller not issue a Write command when the Write Protect signal is true low It is recommended that the Write Data line be inactive whenever Write Gate is false high Circuit Description When a write protected diskette is installed light from the Write Protect E D is detected by the Write Protected sensor transistor The output of the sensor is high and is conditioned by U32 The output at Pin 14 is low generating the signal WR PROT This signal is used internally
39. OTING GUIDE introduction eoi Soros b e Rd era chien etn ee Not Ready and or No Index Will Not Seek or Restore Will Not Write Will NOURGAG ror PP Vido ec oa roD b Activity L E D No Track OO Sensor Indication 9 3G 9 s WO 9 Aou S P 4d ou 5 wo N d B a B M 9 B oV 98 BA gt B 4 n NJ wow 4 B W SECTION V REPLACEMENT PROCEDURES Introduction Drive Belt pa o C de poda Drive Motola SG Se debated rq n CTreurPBoardiu rss ae he pus f Cone Assembly Diskette Lever kate P Fe Era Bridge Assembly Bezel Section Page Number Title of Section Number 5 8 KONE EDEN bt ae sat e s 5 9 5 9 Load Arm Assembly esker Glade a tes di 5 10 5 10 Track OO Sensor 5 10 5 11 Write Protect Sensor Assembly essi bees vanes wees 5 11 5 12 Door Switch Assembly eet ick me E e 5 12 5 13 Index Sensor Assembly cepe eene E eel en 5 12 5 14 Diskette Ejector
40. Radial Head Load Signal ci ex seve ux omo goce e eka Circuit Board ASSGmDIV ies aed ct diro CEA X EDO kr SOROR OX Hub Center Line and Track Cais Eve Palterticu susct VER px a 0 ed SE Head Module Retaining and Cam 5 indexsro Data BUS Cb sa pul S NR Ed eios dod Index Sensor s Retaining Screw and Negative Going Pulse Width Track SENSO cuoc LU RM REL bue E Du dua eed t c Optimum Head Azimuth Head Azimuth Alignment Acceptable Lower Head Azimuth Alignment Acceptable Upper Load Arm Adjustment Front Printed Circuit CER are at eade UR PR nul e E Ra e pa Si Aen Interface Configuration Select Lines Schematic Diagram Write Data Circuit Block Diagram Trim Erase Diagram Side Select Schematic Diagram Index Schematic Diagram Waveform at Test Point 7 Soft Sectored Track 00 Schematic Diagram Write Protect Schematic Diagram Read Circuit Block Diagram Read Data Schematic Diagram Drive Belt and Spindle Drive Motor and Related Parts Circuit Board Mounting Screws Cone
41. Stepper Motor Assembly Key 5 19 Head Carriage Assembly Key 5 20 TABLES Page Title of Table Number Mechanical and Electrical 1 3 Requirements en ee a arr 1 4 Interface Connector Pin 1 13 Power Connector Pin 1 14 lode E PC Mr 1 17 Drive Interface Lines and Pin 3 3 Stepper Truth Fable ror 3 5 SECTION I INTRODUCTION TO THE TM848 FAMILY OF DISK DRIVES 1 INTRODUCTION This section contains a description of the physical and functional specifications for the TM848 1 and 2 disk drives 48 tracks per inch manufactured by Tandon Corporation 1 1 PURPOSE OF THE DRIVE The drive is an eight inch disk memory designed for random access data entry storage and retrieval applications These applications typically are intelligent terminal controllers microcomputers word processing systems data communications systems error logging microprogram loading point of sale terminals and Winchester back ups The drive is capable of recording and reading digital data using FM and MFM 1 2 PHYSICAL DESCRIPTION OF THE DRIVE The drive can be mounted in any vertical
42. TK 7 LOADED DIG 2 gt WHI 5 24 0 gt GRN 2v2 220 SHS PTO 12 DOK id LM2901 RIS 4782 47K laooi TYP TO00LuP NOTE COLORS REFER D MOTOR WIRING 5 L epe e ME tol ORG 7400 DR SEL BE pan 1 035 i HDLOD 9 So MED SK 1 B Lis PG MCI E gt 2 P AB MC2 Ae 205 4 HEAT SINK MOTOR MOT C58 OFF MC po V gt EA MCA BRUSHLESS DC SPINDLE MOTOR CONTROL IAS M sia ae tac E Tandon PRA LUN 4 2 CORPORATION TITLE Sn E TU m tr MOVE ELECTRONICS ME NEN LL pes cL o area 2 APPLICATION nr morene Ps S 3 1 A eet APPENDIX II RECOMMENDED SPARE PARTS LIST PARTS AND SUBASSEMBLIES Part Part Number Drive Belt 210062 000 Drive Motor 210061 000 Circuit Board 210094 000 Cone Assembly 210085 000 Diskette Lever 210084 000 Bridge Assembly 210086 000 Bezel 21001 1 000 Activity L E D Front Panel 210081 000 Load Arm Assembly 210089 000 Track 00 Sensor Assembly 210080 000 Write Protect Sensor Assembly 210079 000 Door Open Switch Assembly 210083 000 Index Sensor Assembly 210075 000 Diskette Ejector Assembly 210124 000 Head Carriage Assembly Single Sided Recording 210065 001 Double Sided Recording 210065 002 _ Stepper Motor Mounting As
43. ace between the upper head and the diskette The upper head should not hit the diskette when inserting and ejecting it ADJUSTMENT SCREW LOADING CAM LOAD ARM 015 INCH MINIMUM PLATEN Figure 2 12 Load Arm Adjustment Front View 2 12 SECTION III PRINTED CIRCUIT BOARD OPERATION 3 INTRODUCTION This section contains the interface description and the circuit board theory of operations for the 848 family of disk drives In addition Sections 3 1 and 3 2 contain schematic diagrams of the circuit boards installed in the drive 3 1 PHYSICAL DESCRIPTION OF THE CIRCUIT BOARD The printed circuit board 15 approzimately 12 50 inches long by 5 25 inches wide Figure 3 1 contains an illustration of the placement of test points and connectors ALTERNATE TEST POINT INDEX TRIGGERING R33 TP11 9 O TP12 50 7 P2 P3 P10 P1 P11P12 Figure 3 1 Printed Circuit Board 3 2 INTERFACE ELECTRONICS SPECIFICATIONS All interface signals are TTL compatible Logic true low is 0 4 volt minimum Figure 3 2 illustrates the interface configuration The maximum interface cable length is ten feet 150 OHMS TWISTED PAIR 74LSO4 OR EQUIVALENT TRUE TRUE TRANSMISSION LINE 10 FEET g 7919 OR EQUIVALENT ee J ORIVER RECEIVER 1 Figure 3 2 Interface Configuration 3 1 It is recommended that the interface
44. ad 1 21 1 19 16 Head Load Alternate Output Pad 1 21 1 19 17 Radial Head Load Signal Option a cece ARR ere e AS 1 21 Section Number 1 19 18 1 19 19 1 19 20 1 19 21 1 19 22 Title of Section Inhibit Write When Write Protected Allow Write When Write Protected Head Side Select Options 51 53 Spindle Motor Control Options 1 4 Motor Control Select Options MC1 MC4 SECTION MAINTENANCE CHECKS AND ADJUSTMENTS 2 2 1 2 1 1 2 2 2 2 1 2 3 2 4 2 4 1 2 4 2 2 4 3 MU OUR E aO Uta etin M abd Spindle Drive Motor Checks and Long Term Drive Motor Speed Checks and Adjustments Cats Eye Alignment Check and Adjustment Cats Eye Alignment Check Head Carriage Adjustment cisco e Rex E EE a anh Index Sensor Checks and Adjustments Index To Data Burst Checks Index Sensor Adjustment index Pulse Width Check aat eee Se oe bw dae RD Et eras Track OO Sensor Check and Adjustment Amplitude Check Azimuth Check SECTION IlI PRINTED CIRCUIT BOARD OPERATION Ut OCUCDOL Ne Physical Description of The Circuit Board Interface Electronics Specifications Input Control EIS s socie eta cer ee aa co uter etc a petet iive Output Control Lines SECTION IV TROUBLESHO
45. advancement of the read write carriage In addition to the logic necessary for motor control gate is provided that inhibits positioner motion during a write operation 1 15 5 Data Electronics Information can be recorded on the diskette by using a double frequency code Figure 1 3 illustrates the magnetization profiles in each bit cell for the number sequence shown for FM recording BIT PATTERN BIT CELL WRITE DATA 0 i i Apr MAGNETIC ELEMENTS Ni sls NIN SIS NAN 1 SIS NN 545 NEN SIS NIN 515 Figure 1 3 FM Recording Magnetization Profiles The erase gaps provide a guard band on either side of the recorded track All signals required to control the data electronics are provided by the user system and are shown in the TM848 drive functional block diagram see Figure 1 2 These control signals are 1 2 3 4 5 Select Write Gate Write Data Side Select Write Current Switch Composite read data is sent to the user system via the Read Data interface line A Data Recording The write electronics consist of a switchable write current source a write waveform generator an erase current source the trim erase control logic and the head selection logic see Appendix I The read write winding on the head is center tapped During a write operation current from the write current source flows in al
46. al Description When the drive is selected the write data line provides the bit serial Write Data pulses that control the switching of the write current in the heads The write electronics must be conditioned for writing by the Write Gate line For each high to low transition on the WRT DATA line aflux change is produced at the head write gap This causes a flux change to be stored on the diskette see Figure 3 4 N INTERNAL WRITE BUSY SIDE SELECT LOGIC WRITE READ DRIVER 1 SIDE SELECT WRITE DATA TRIGGER N WRITE DATA WRITE DRIVER 2 ERASE COIL NWRITE GATE N WRITE PROTECT UNIT SELECT ERASE CURRENT SOURCE INTERNAL DISABLE WRITE BUSY Figure 3 4 Write Data Circuit Block Diagram When a double frequency type encoding technique is used in which data and clock form the combined Write Data signal it is recommended that the repetition of the high to low transitions when writing all zeros be equal to the nominal data rate 0 1 percent The repetition rate of the high to low transitions when writing all ones should be equal to twice the nominal data rate 40 1 percent The data transfer rate for a 1F pattern is 250 000 Bits Per Second BPS The data transfer rate for a 2F pattern is 500 000 BPS 3 6 Circuit Description Data is sent to the drive via interface Pin 38 This signal is inverted by 022 and is used to clock the D flip flop U23 The outputs of U23 are inverted subse
47. alled This output signalis present at the interface 3 TheWrite Protect sensor disables the drive s write electronics whenever a write enable tab is removed from the diskette see Section 1 12 1 4 DISKETTES The drive uses a standard eight inch diskette Diskettes are available with a single index hole or with index and sector holes They also are available double or single sided Single index hole diskettes are used when sector information is pre recorded on the diskette soft sectoring Multiple index hole diskettes provide sector pulses by means of the index sensor and electronics hard sectoring 1 5 MECHANICAL AND ELECTRICAL SPECIFICATIONS The mechanical and electrical specifications of the drive are listed in Table 1 1 1 6 POWER REQUIREMENTS The power requirements of the drive are listed in Table 1 2 1 7 INTERFACE CIRCUIT SPECIFICATIONS The interface circuits are designed so that a disconnected wire results in a false signal Levels True 0 4 V maximum False 2 4 V minimum 1 8 INCOMING INSPECTION CHECKS AND PROCEDURES There are two kinds of recommended incoming inspection checks and procedures static and dynamic ones The static incoming inspection checks include the minimum steps that should be taken to ensure that the drive is operational when received TABLE 1 1 MECHANICAL AND ELECTRICAL SPECIFICATIONS MECHANICAL Height 2 30 inches Width 8 inches ELECTRICAL 5 V Power 24 V D C Po
48. e Protected is factory installed 1 19 19 Allow Write When Write Protected NP This option allows the controller to write on any diskette whether or not is is write protected 1 21 Note This option does not stop the write protect signal from being sent on the interface line This option is implemented by cutting WP and by installing NP 1 19 20 Head Side Select Options 51 53 This option allows heads to be selected by side select drive select or the direction control signal The drive comes with side select S2 installed To use the drive select line to enable the heads cut 52 and install 53 along with the proper 1B 4B jumper that is used with S3 see 1B 4B For head selection using Direction Select cut S2 and install 81 1 19 21 Spindle Motor Control Options M1 M4 M1 is used to enable the motor off delay timer When this jumper is installed the drive motor is enabled and disabled by either the drive select M3 or head load M4 commands A 20 second turn turn off delay of the spindle motor is activated on the trailing edge of the controlling signal 2 is used for radial motor control independent of the motor control functions installed with M1 and MA M2 should be in if the user wishes to enable the drive motor continuously orto use the radial motor on line MC1 MCA M3 is used to control the drive motor using drive select When the drive select line goes low true the drive motor comes up to speed i
49. e is only required if faithful reproduction of the first write data transition is signifcant At the end of recording at least one additional pulse on the write data line must be inserted after the last significant write data pulse to avoid excessive peak shift effects NOTE 1 TER T fl 2 WRITE GATE 4 190 sec 650 4 TRIM ERASE I 1 INTERNAL WRITE 1 BUSY eR i WRITE DATA pe 2 1 WRITE WAVEFORM GENERATOR 1 1 p 1 NOTE 44 i i l NOTES 1 0 700 MILLISECONDS AFTER DRIVE MOTOR 3 10MAPEAKTOPEAK TRACKO STARTS OR 20 MILLISECONDS AFTER LAST STEP TRACK 42 7 5 MA PEAK TO PEAK PULSE WHICHEVER IS THE LATEST TIME TRACK 43 TO TRACK 77 2 UNSYCHRONIZED 4 2USEC MINIMUM 4 USEC MAXIMUM Figure 1 4 Write Operation Timing Diagram The duration of a write operation is from the true going edge of write gate to the false going edge of erase This is indicated by the internal write busy waveform shown see Figure 1 4 The Read electronics consist of 1 Read Switch Side Select 2 Read Preamplifier 3 Filter 4 Differentiatior 5 Time Domain Filter and Digitizer The read switch is used to isolate the read amplifier from the voltage excursion across the head during a write operation The side select is used to
50. ecks After turning the drive motor on check that the drive belt does not slip or fall off the large pulley Check the spindle speed see Section II DRIVE MOTOR Removal Remove the drive belt see Section 5 1 After turning the drive over cut the tie wraps that hold the drive motor s wires see Figure 5 2 Unplug P6 from the circuit board Remove the three mounting screws that attached the drive motor tothe chassis Lift out the drive motor Installation Set the drive motor on the chassis aligning the three mounting holes Reinstall and tighten the three mounting screws 5 2 5 2 3 B 5 3 5 3 1 5 3 2 DRIVE MOTOR aca mis a MIR cu I T 1 MOUNTING SCREWS TIE WRAPS 3 PLACES DRIVE MOTOR WIRES 12 PLACES Figure 5 2 Drive Motor and Related Parts Carefully rebundle the wires including the drive motor wire and cable harness them see Figure 5 2 Plug P6 into the circuit board Turn the drive over and reinstall the drive belt see Section 5 1 2 Checks Check to ensure that the drive motor works Check the spindle speed see Section 11 CIRCUIT BOARD Removal Remove all the connectors from the circuit board Remove the two side mounting screws that connect the two regulator heat sinks to the drive s chassis see Figure 5 3 Remove the screw and the retaining clip that attach
51. enable one of the read write erase heads The drive must be ina ready condition before reading can begin As with the data recording operation this ready condition must be established by the user system In addition to the requirements established in this section a period of 100 microseconds is necessary after a trim erase operation occurs to allow the read amplifier to settle after the transient caused by the read switch returning to the read mode 1 11 The output signal from the read write head is amplified by read preamplifier and filtered by low pass linear phase filter to remove noise see Figure 1 5 The linear output from the filteris passed to the differentiator which generates a wave form whose zero crossovers correspond to the peaks of the Read signal This signal is then fed to the zero crossing detector and digitizer LINEAR OUTPUT FROM FILTER OUTPUT FROM DIFFERENTIATOR DIFFERENTIAL DROOP READ DATA INTERFACE t 0 Figure 1 5 Read Timing Diagram Note T O is defined as 250 milliseconds after drive motor starts or 20 milliseconds after a step command 100 microseconds after termination of write busy whichever is the latest time The zero crossover detector and digitizer circuitry generate 200 nanosecond read data pulse corresponding to each peak of the read signal The composite read data signal is sent to the user system via the read data interface line 1 16 INTERFACE ELECTRONICS All inter
52. es the track access motion The direction of motion is determined by the logic state of the Direction line when a Step pulse is issued The motion is toward the center of the drive if the Direction line is in the true low state when a Step pulse is issued The direction of motion is away from the center of the drive if the Direction line is in the false high state when a Step pulse is issued To ensure proper positioning the Direction line should be stable fora minimum of 100 microseconds before the trailing edge of the corresponding Step pulse The Direction line should also remain stable until 100 microseconds after the trailing edge of the Step pulse The access motion is initiated on the trailing edge of the Step pulse When the carriage is positioned at Track and the stepper motoris at Phase 0 the signal at Pin 42 of P13 goes true low indicating that Track OO has been reached When stepping in or out Test Point 8 is a high going pulse for each step pulse issued 3 4 Circuit Description The Direction line comes in on Pin 34 of the interface connector high signal directs the step logic to step toward Track 00 low signal directs the step logic to step toward higher numbered track The direction line sets the proper phase to the exclusive OR gates of U9 TABLE 3 2 STEPPER LOGIC TRUTH TABLE Step Out Toward Track 00 Step In Toward The Upper Tracks Phase Phase Pin No 0 3 2 1 0 Pin No 1 2 3 0 U21 9 0 1 1 0 0
53. face signals are TTL compatible Logic true low is 0 4 volt maximum logic false high is 2 4 volts minimum The maximum interface cable length is ten feet It is recommended that the interface cable be flat ribbon cable that has a characteristic impedence of 100 ohms 1 16 1 Interface Connector Pin Assignments P13 The interface connector pin assignments P13 are listed in Table 1 3 1 16 2 Power Connector Pin Assignments The power connector pin assignments are listed in Table 1 4 Ground TABLE 1 3 INTERFACE CONNECTOR PIN ASSIGNMENTS Pin Number Signal Write Current Switch Motor Off Control 1 Motor Off Control 2 Motor Off Control 3 Two Sided option Model TM848 2 only Disk Change option Side Select Model TM848 2 only Activity Indicator option Head Load Index Ready Motor Off Control 4 Drive Select 1 Side Select Option TM848 2 only Drive Select 2 Side Select Option TM848 2 only Drive Select 3 Side Select Option TM848 2 only Drive Select 4 Side Select Option TM848 2 only Direction Select Side Select Option TM848 2 only Step Write Data Write Gate Track 00 Write Protect Read Data Alternate I O Alternate 1 TABLE 1 4 POWER CONNECTOR PIN ASSIGNMENTS Pin Supply Voltage 24V D C Return Return Return 5V D C OT19c00 2 1 17 TERMINATED LINES 1 17 1 Input Line Terminations From Removable Resistor Pack The drive has the capability of terminating the following inp
54. installed All of the motors are enabled when the Head Load line goes true low M1 should be installed if a motor turn off delay is desired See Section 1 19 21 for an additional description of this circuit When a Drive Select line is to be used for Motor Enable M3 must be installed This enables the drive motor when the Select line goes low Circuit Description When the motor is enabled by any ofthe above U35 Pin 6 floats high allowing the speed control U41 to start the drive motor Two Hall Effect transducers in the motor supply the necessary feedback signals for proper speed regulation When U35 6 goes high the output of U41 Pin 6 turns on Q21 which in turn applies a varying voltage to Q20 that regulates the amount of current through Q20 and the motor driver transistors Q1 through Q4 Transistors Q1 through Q4 are turned on by the gated pulses derived from the conditioned outputs of the Hall Effect transducers The conditioned output of U38 Pin2 is subsequently conditioned by Gate U36 which acts as an edge trigger and pulse doubler This signal is fed back to U41 Pins 2 and 3 which results in closed loop speed control The drive motors rotational speed is approximately 2520 RPM when adjusted to give a spindle speed of 360 RPM C DIR STEP Direction and Step Lines Functional Description When the drive is selected a true low pulse with a time duration between 200 nanoseconds 2 milliseconds on the Step line initiat
55. is high and a true disk change status is sent to the interface on Pin 12 from U4 1 1 Flip U10 is set on the trailing edge of drive select causing U10 6 to go low and setting the disk change status to the false state In actual use this signal can be used by the host controller to determine that the diskette lever has been opened since the end of the previous drive select operation SV Die 2 R fo Bep 220MS ras PRIN 49 We p SPIN N c jus A AUT xn HY 12d MTRON 1500 552 INDEX are met Ae Tr gt 200 300 INDEX pa PR A m 5 2 OG DS I READY D 2 q gt 5 a 9 50 504 02 READY LEE c 5 READ 1 NC R y y 7474 Figure 3 7 Index Schematic Diagram gt 2ms Figure 3 8 Waveform at Test Point 11 or 12 Alternate Test Point R33 Soft Sectored Diskette Installed D TRK 00 Functional Description When the drive is selected the Track 00 interface signal indicates to the controller that the read write head is positioned at Track 00 The Track 00 signal remains true low until the head is moved away from Track OO The Track 00 sensor is activated internally between Tracks 2 and 3 Interface Pin 42 see Figure 3 9 is true low when the carriage is positioned at Track 00 and the step motor is at Phase 0 3 11 TRACK LE
56. iskette lever activates the cone clamp system resulting in centering of the diskette and clamping of the diskette to the drive hub The drive hub is driven ata constant speed of 360 RPM bya servo controlled brushless D C motor The head is loaded into contact with the recording medium whenever the diskette lever is latched 1 1 The head is positioned over the desired track by means of a stepper motor band assembly and its associated electronics This positioner employs 3 6 degree rotation to cause one track linear movement When write protected diskette is inserted into the drive the Write Protect sensor disables the write electronics of the drive and Write Protect status output signal is available to the interface When performing write operation 0 013 inch wide nominal data track 15 recorded This track 18 then tunnel erased to 0 012 inch nominal Data recovery electronics include a low level head amplifier a differentiator a zero crossing detector and digitizing circuits No data clock separation is provided In addition the drive is supplied with the following sensor systems 1 A track OO sensor that senses when the Head Carriage Assembly is positioned at Track OO 2 The two index sensors each of which consists of a L E D light source and a phototransistor are positioned so that a signal is generated when a index hole is detected The drive can determine whethera single or double sided diskette is inst
57. n less then 500 milliseconds and becomes ready in less than 700 milliseconds After the drive select line goes false high the motor will run for 20 seconds To implement this option install a jumper at location M3 For correct operation of M3 remove M4 is used to start the drive motor using the head load interface lines When the head load line goes low true the drive motor comes up to speed in less than 500 milliseconds and becomes ready in less than 700 milliseconds After the head load line goes high false the motor will run for 20 seconds To implement this option remove M3 for correct operation of option M4 1 19 22 Motor Control Select Options MC1 MC4 This option is used the drive motor is to be enabled independent of drive select or head select When these lines are low true the motor is off The drive comes without this option installed This option does not operate the time out delay circuit Toimplementthis option that controls the drive motor using an MCxline install the appropriate MC1 MCA jumper When using this option M2 must be installed If the motor turn off delay is desired the delay can be triggered by Drive Select or Head Load commands when used in conjunction with M3 or 4 1 22 SECTION II MAINTENANCE CHECKS AND ADJUSTMENTS 2 INTRODUCTION This section is for the use ofthe Repair Department It contains checks and adjustments that are used during the normal life of the drive Bef
58. nd its wires after unplugging P11 Installation Install the Activity L E D into the bezel Install the bezel Attach the Activity L E D wires to the chassis with brackets see Figure 5 11 Plug P11 into the circuit board Checks Ensure that the Activity L E D does not interfere with the drive mechanisms Ensure that the Activity L E D goes on when required 5 9 5 9 5 9 1 LOAD ARM ASSEMBLY Removal A Remove the circuit board see Section 5 3 1 B Remove the mounting screw and washer that are used to attach the Load Arm Assembly to 5 9 2 5 9 3 5 10 5 10 1 the chassis see Figure 5 12 LOAD ARM REAR MOUNTING SCREW WASHER AND SPRING Figure 5 12 Load Arm Assembly Key Parts Carefully slide out the Load Arm Assembly toward the rear of the chassis Installation Slide the Load Arm Assembly into position from the rear of the chassis ensuring that the load spring is sitting under the front of the mounting screw Install and tighten the mounting screw that attaches the Load Arm Assembly to the chassis ensuring that the washer is under the screw and that the head lift arm is over the Load Arm Assembly Install the circuit board see Section 5 3 2 Checks Insert a diskette in the drive Ensure that the head is loaded when the diskette lever is activated and that adequate clearance is attained for diskette insertion and ejection see Section 1
59. nel A To appropriate index test point see Section 2 Item Number 1 Ground Test Point 1 Time Base 5 millisecond per division Voltage 2 volts per division Trigger Negative leading edge of Channel A appropriate test point B Ensure that the negative going pulse width is between 1 0 and 2 3 milliseconds see Figure 2 T 1 8 to 2 3 milliseconds Figure 2 7 Negative Going Pulse Width 2 5 TRACK 00 SENSOR CHECK AND ADJUSTMENT The Track OO sensor provides a signal that identifies Track OO to the logic electronics A Track OO signal is sent to the controller on Pin 20 of the interface A Apply power to the drive B Load an alignment diskette into the drive C Step the carriage to the radial alignment track Track 38 see Section 2 2 2 8 D Confirm the position by observing the Cats Eye pattern E Attach Channel A to Test Point 10 F Restore the carriage to Track 00 and ensure that the Track 00 L E D on the exerciser turnson G Seek to Track 1 and ensure that the signal at Test Point 10 is high H Seek to Track 2 and ensure that this line is low or in transition Seek to Track 3 and ensure that this line is low J If the signal is incorrect restore to Track OO with the oscilloscope attached as above K Seek out to Track 2 and loosen the two retaining screws that hold the Track OO sensor see Figure 2 8 ie VE TRAGK 00 SENSOR SGD pat Or li
60. nfigured to allow only the Index 1 signal to be present on the interface when a two hole diskette envelope is used When a double sided diskette is installed the signal IN1FF is generated and gated by U4 to enable the output TWO SIDED B Ready Functional Description Ready is used by the controller to ascertain the status of the drive This signalis generated when the drive motor is on the diskette installed and the drive is selected The signal takes less than 700 milliseconds to go true low from a motor start by Drive Select or Head Load see Section 1 19 21 Circuit Description The index pulse is gated by U5 which in turn triggers U17 a 220 millisecond retriggerable one shot When the index to index time becomes less than 220 milliseconds the one shot becomes continuously enabled and generates the signal SPIN This signal is gated with POR Power On Reset to enable the two revolution counters U18 The output of U18 Pin 8 enables U6 whose output is gated with Drive Select to generate the signal ready Whenever the drive motor is disabled MTRON goes low causing this sequence to be repeated when the motor is restarted C Disk Change Functional Description The signal DISK CHANGE is used to indicate the host controller that a disk change operation has been made 3 10 Circuit Description The disk change flip flop U10 is reset by OPEN whenever the lever is the open position When this occurs U10 6
61. nstall jumpers at these locations see Section 1 18 1 19 12 Disk Change DC This output is used to indicate to the controller that a disk change has been made The internal signal is gated with drive select When the lever is opened the disk change line goes low true and stays low until the trailing edge of the next drive select 1 19 13 Two Sided Diskette Installed 25 When a two sided diskette is installed internal circuitry gates this signal with drive select and sends a low true signal to the controller which means that a double sided diskette is installed index hole two is present The Two Sided Diskette Installed option is factory installed 1 20 1 19 14 Stepper Power From Drive Select DS This option allows the user to remove D C power from the stepper motor using drive select which results in lower stand by current consumption The Stepper Power From Drive Select option is implemented by installing DS and cutting HL 1 19 15 Stepper Power From Head Load Line HL This option supplies power to the stepper motor when the head load line goes low true This results in lower stand by current consumption This option is factory installed DS must be removed for proper operation 1 19 16 Head Load Alternate Output Pad Option This option allows the userto load and unload the head load solenoid optional and along withthe HL and Y options enables the stepper motor and lights the Activity L E D
62. or horizontal plane However when mounted horizontally the printed circuit board must be up The spindle is belt driven by a brushless D C motor with an integral tachometer The servo control circuit suitably sized pulleys and the tachometer control the speed of the spindle The Read Write double sided head assembly is positioned by means of a stepper motor split band and a pulley The Read Write Erase head assembly is a glass bonded manganese zinc ceramic structure It has life in excess of 20 000 hours For diskette loading operator access is provide via a slot located on the front of the drive The electronic components of the drive are mounted on a circuit board assembly located in the chassis Power and interface signals are routed through connectors that plug into the back of the drive 1 3 FUNCTIONAL DESCRIPTION OF THE DRIVE The drive is fully self contained It requires no operator intervention during normal operation The drive consists of a spindle drive system a head positioning system and a read write erase system The TM848 1 is a single sided drive The TM848 2 is a double sided drive The only difference between the two drives is the number of heads The circuit board is identical in both models When the diskette lever is opened access is provided for the insertion of a diskette The diskette is accurately positioned by plastic guides The disk position is ensured by the backstop and disk ejector Closing the d
63. ore applying power to the drive or doing any checks or adjustments visually inspect the drive to ensure that it has no missing or broken parts The following equipment is required for checks and adjustments 1 dual channel wideband oscilloscope Tektronix 465 or equivalent 2 An exerciser or software routine capable of stepping the drive to any track selecting the upper or lower head and writing 1F all zeros if FM or a 2F all ones if FM pattern on the disk 3 A Phillips screwdriver 4 set of Allen wrenches 5 A flat blade screwdriver 6 blank diskette 7 An alignment diskette Dysan P N 360 2A or equivalent 8 Integrated circuit dip clips 14 and 16 pin 2 1 SPINDLE DRIVE MOTOR CHECKS AND ADJUSTMENTS The long term drive motor speed adjustment ensures that the motor s speed is within the range of tolerance specified The motor speed specification is 360 RPM 1 25 percent 2 1 1 Long Term Drive Motor Speed Checks and Adjustments A Preliminary checks required Verify power 24V D C 10 percent 5V D 5 percent B Apply power to the drive C Activate the drive motor on the interface line D Insert work diskette E Set up the oscilloscope as follows Voltage 2 volts per division Time Per Division 20 milliseconds Trigger Negative Channel A R33 Note For the TM848 1 single sided drive trigger off of R33 For the TM848 2 double sided drive trigger off of Test Point 12
64. quently and used to drive Q15 and Q17 which direct the write current to the correct winding F TRIM ERASE Functional Description The TM848 uses tunnel scheme to achieve trim erase which is used to guard band around the data tracks allowing minor track offsets and minor misalignment without data errors occurring The erase poles are staggered 036 inch behind the read write poles At a media rotational speed of 360 RPM the tunnel erase method requires that the trim erase be delayed for 190 microseconds afer the start of writing and that it be continued for 550 microseconds after the end of writing the data The two one shots in U30 provide these delay time intervals When the write gate goes low U30 Pin 9 A input is triggered and a high to low to high transition of 190 us is generated The write gate is also applied to U30 Pin 1 A input When the write data is applied to the WRT DATA line U23 conditions the data which in turn generates the signal WRT TRAN write transition This signal is then applied to U30 Pin 2 B input which is a positive triggered input This clock will retrigger this one shot continuously until the last transition of the WRT TRAN and WRT GATE occurs At this time the one shot stays on for an additional 550 us These outputs U30 Pins 12 and 13 are gated by U31 which is the trime erase gate This output goes low whenever both inputs are high causing the trim erase to be enabled
65. running a wire from U4 Pin 6 to the appropriate alternate I O lines If use of MC1 is desired interface line 20 may be used as one index line In this case the shunt pack U3 6 11 remains intact on one drive see Figure 1 9 PROGRAM SHUNT PINS 6 10 ARE OPENED INDEX _ DRSEL RI INDEX ETCH CUT aS L NE p ETE OG eT RADIAL INDEX gt STATUS TO USER E yc CONTROLLER Figure 1 9 Radial Index Installation 1 19 9 Index Alternate Output Pad 1 The internal index pulse is gated with drive select to give a low true signal at Pad I This option should be left connected for the controller to receive the index pulse See Radial Index for other uses of this line The Index Alternate Output Pad option is factory installed 1 19 10 In Use Alternate Output Pad D This line may be used to latch a lever lock solenoid which is an optional feature A low true command is sent by the controller to Pin 16 of interface connector P13 Then this signal is used with drive select to latch the locking solenoid by pulsing drive select with IN USE low The solenoid is unlatched when drive select is pulsed and IN USE is high To implement this option locate option pads D and DL Install jumpers at these locations 1 19 11 Diskette Lever Lock Latch Option DL This option is used in conjunction with in use alternate output pad Toimplementthis option locate option pads D and DL I
66. see Figure 3 5 G SIDE SELECT Functional Description SIDE SELECT can be generated three ways See the option listing Section 1 19 for this information As shipped from the factory the side is selected using the SIDE SELECT interface line When the Side Select signal is low Side 1 the upper head of the drive is selected for read write operations When this signal is high Side O of the drive is selected see Figure 3 6 The Side Select signal must be stable during an entire read or write operation This signal is best implemented in synchronization with the Drive Select line signal Circuit Description As shipped from the factory the Side Select signal is received on Pin 14 of edge connector P13 This signal is received by U22 inverted then inverted again by U13 The output of U13 Pin 10 generates the signal called Side 1 The Side 1 signalis applied to U13 Pin 9 and U24 Pin 13 The output of 013 Pin 8 is applied to U24 Pin 1 This output at Pin 2 of U24 isthe opposite of U24 Pin 12 The resistor divider network sets up the biasing voltages to turn on and turn off the head select transistor Q18 or Q19 The head biasing voltages seen across the collector resistors will be 5 2V D C when selecting a head for a read operation 12V D C during a write operation and OV D C when the head is not selected The emitter voltages on 018 and Q19 will always be the opposite of each other causing center tap
67. sembly 210090 000 Stepper Band 210112 000 Load Power Resistors 210076 000 Diskette Lever Lock 210082 000 Ejector Spring 210036 000 Load Arm Spring 210122 000 Note All components are standard commercial parts purchased to original equipment manufacturer s specifications OPERATING AND SERVICE MANUAL TM848 1 AND TM848 2 THINLINE DISK DRIVES 48 TANDON P N 179031 001 ALIGNMENT DISKETTE Recommended Dysan 800690 Model Number 360 2A 1 1 P N 179031 001 1082
68. serierion fonre om Ja b PROD RELEASE 40002 250 DA Va CHANGED PER 40056 OL m CHANGED PER E 0 40095 CHANGED 0 40134 SELECTION em NECS LOGIC DR SHY 50 1 C26 5 ul 220MS PR 4 DY 02 5 MTRON 1500 2 APPLICABLE PC BOARD REV LEVEL 210060 000 REV D APPLICABLE ASSY REV LEVEL 210094 000 REV GJ MODEL 848 DISKETTE DRIVE ELECTRONICS BREAK ALL 7 APPLICATION 5 4 3 EEG TE TREE espere D 54K ATK 45V UR WRT DATA 30 gt HEAD CONNECTOR WRPROT 4 an SHIELD DRSEL N gt a ae WR VER 3 5 ware R T m ew 528 V T E 2 READ WRITE AU RDZ 5 12V Be E ERASE D LOWER HEAD CURRENT SUCH WRITE ELECTRONICS iu UPPER HEAD EEE ER a ER EEE EE ME CER E CR3O READ WRITE I B INT BUSY 4 c gs ERASE a R79 ERASE 5 z par 220 1 75462 n SHIELD 1 3 37 READ URITE HEAD ASSY L ERASE ELECTRONICS Z ___ _________________ Pit oa tanpon wagmencerne SIGNATURES D
69. slot must be covered to write on the diskette An option is available on the board for defeating the write protect sensor 1 13 OPERATION OF THE DRIVE The drive consists of the mechanical and electrical components necessary to record and to read digital data on a diskette User provided D C power at 24 volts and 5 volts is required for operation of the drive 1 14 ORGANIZATION OF THE DRIVE All electrical subassemblies in the drive are constructed with leads that terminate in multipin connectors enabling the individual assemblies to be removed The heads are connected to the circuit board via cables that terminate in five pin female connectors and their associated male sockets that are located in close proximity to the read write data electronics Interface signals and power are provided via connectors at the rear of the drive 1 15 COMPONENTS OF THE DRIVE The drive consists of six functional groups 1 Index Pulse Shaper 2 Drive Status Logic A Write Protect B Track 00 Sensor C Double sided Disk D Ready E Disk Change 1 7 3 Spindle Drive Control 4 Carriage Position Control 5 Write Erase Control 6 Read Amplifier and Digitizer Figure 1 2 is a functional block diagram of the drive It should be referred to in conjunction with the following sections The data in the ensuing figures is primarily represented in simplified form 1 15 1 index Pulse An index pulse is provided to the user system via the index pulse
70. so goes to the ready circuitry at U6 5 to disable Ready in the event that the upper head Head 1 is selected when a single sided Head 0 diskette is installed see Option RM for further discussion GL E 12V KIDS Figure 3 12 Read Data Schematic Diagram SECTION IV TROUBLESHOOTING GUIDE 4 INTRODUCTION This section is presented in the form of a table Each section contains four major parts 1 The section number 2 statement of the presenting condition 3 A list of the possible causes of the condition 4 The recommended action to be taken SECTION 4 1 4 2 CONDITION NOT READY AND OR NO INDEX WILL NOT SEEK OR RESTORE POSSIBLE CAUSE Diskette not inserted Diskette not clamped Unit not selected Drive motor not turning Index sensor not connected Index sensor defective Interface not enabled Step motor disconnected Defective step logic Defective stepper motor Wrong option selected 4 2 RECOMMENDED AGTION Insert diskette Turn knob lock lever clockwise so that it is perpendicular to the diskette insertion slot Verify unit select and jumper configuration Verify interface drive motor on Check Connector P6 Verify drive belt installed Replace circuit board Replace Drive Motor Assembly Check 1 Replace index sensor Verify interface direction step and select signals Check Connectors P4 and 5 Replace circuit board Replace
71. ternate halves of the winding under control of the write waveform generator The conditions required for recording i e drive ready must be established by the user s system as follows 1 Drive speed stabilization occurs 700 milliseconds after the drive motor is started 2 Subsequent to any read write operation the positioner must be allowed to settle This requires 18 milliseconds maximum after the last step pulse is initiated i e 3 milliseconds for the step motion and 15 milliseconds for settling 3 The foregoing operations can be overlapped if required Figure 1 4 illustrates the timing diagram for a write operation Att 0 when the unit is ready the write gate interface line goes true This enables the write current source Write current is switched via the write current switch interface line to a lower value by the user s controller at Track 43 The Trim Erase control goes true 190 microseconds after the Write Enable interface line since the trim erase gaps are behind the read write gap It should be noted that this value is optimized betweenthe requirements at Track OO and at Track 76 so that the effect of the trim erase gaps on previous information is minimized Figure 1 4 shows the information on the write data interface line and the output of the write waveform generator which toggles on the leading edge of every write data pulse maximum of 4 microseconds between write gate going true and the first write data puls
72. the D C blocking capacitors to the crossover detector U8 which digitizes the signal This converts the signal into standard TTL level Integrated circuits U9 U11 and 010 comprise a comparator circuit Any pulses that occur outside of the normal duty cycle of Ut 1 eliminated U9 is an edge detector U11 acts as a one shot with a timeout of approximately 860 nanoseconds U10 is the actual comparator The Read signal is presented to U9 Then it goes to U11 where the pulses are shaped to 200 nanoseconds This output is gated at U29 with the Unit Select signal to produce a digital output at Pin 46 of the interface connector see Figure 3 12 Note U11 the final one shot is disabled when the drive is writing data onto the diskette G Two Sided Functional Description This output enables the controller to determine if a diskette is installed which utilizes the Index 2 index hole This may be used to indicate to the host controller that a two sided diskette is in the drive TEST POINT 2 UPPER READ AND HEAD SWITCHING SIGNAL CIRCUITS AMPLIFIER TEST POINT 3 HEAD TEST POINT 4 TIME DOMAIN DIFFERENTIATOR CROSSOVER DETECTOR FILTER TEST POINT 5 DIGITIZER DATA OUTPUT INT WRT BUSY UNIT SELECT Figure 3 11 Read Circuit Block Diagram Circuit Description When a two sided diskette is installed the signal IN1FF is generated and gated by U4 to enable the low going output Two Sided The IN1FF signal al
73. the circuit board to the dirve s chassis Lift the circuit board away from the drive Remove the power connector by pushing down on its top Lift its wires out using the slot provided see Figure 5 3 Installation Install the power connector by rethreading the power wires and pushing in the power connector from the back of the drive 5 3 MOUNTING SCREWS CONNECTING HEAT SINKS SS et Q C POWER CONNECTOR T Ly RETAINING CLIP screw Figure 5 3 Circuit Board Mounting Screws B Remount the circuit board using the two screws to the two heat sinks and the screw and nylon clip that attach the circuit board to the drive s chassis C Plug in all connectors ensuring that each one is seated correctly in its proper location 5 3 3 Checks A Verify the select and options configuration B Applying power check the operation of the drive 5 4 CONE ASSEMBLY 5 4 1 Removal A Remove the screw that attaches the cone bracket to the cone alignment arm see Figure 5 4 B Unlatch the diskette lever C Swing the Cone Assembly up 90 degrees so that it points toward the side of the drive D Carefully remove the E Ring flat washer and washer that holds on the cone shaft E Gently lift out the Cone Assembly 5 4 2 Installation A Gently insert the Cone Assembly B Carefully insert the E Ring flat washer and wave washer that holds on the cone shaft see Figure 5 5 C Swing the
74. tions exist for the relationship between the last Write Data pulse and the termination of the Write Gate signal When the Write Gate line goes false high the trim erase will stay on for 550 microseconds see Trim Erase page 3 7 When a write protected diskette is installed in the drive the write electronics are disabled irrespective of the state of the Write Gate line Check the list of options see Section 1 19 for exceptions and further discussion of write protect options Stepping is also disabled by a true low Write Gate Tandon Corporation recommends that the controller wait one millisecond after the WRT GATE goes high false before any step pulses are sent to the drive Circuit Description A low true WRT GATE signal is applied to Pin 40 of the interface connector P13 This signal is 3 5 inverted and gated with Write Protect and Drive Select to enable 023 and Q13 Transistors 013 and Q12 are write current switches Q13 and Q12 are on in parallel when the low Write Current interface is high false This results in a write current of 10 milliamps When the low Write Current line goes low true transistor Q12 turns off and the current decreases to 7 milliamps R52 and R51 determine the amount of write current supplied to the head The network CR18 CR19 CR20 R80 and R81 is a power loss write disable If a sudden voltage loss occurs transistor Q14 turns off disabling the write current E WRT DATA Function
75. tus of the drive The Ready Alternate Output Pad is factory installed 1 19 6 Radial Ready RR This option allows the userto monitor the ready status of all drives without selecting them This option cannot be used concurrently with individual motor control lines for each drive see Figure 1 8 Radial Ready is implemented by punching out Option R between Pins 7 and 10 of U3 by etch cutting RR then by running a wire from U4 Pin 3 to the desired alternate output lines 4 6 8 and 24 PROGRAM SHUNT PINS 7 10 ARE OPENED SIDE 1 1502 IN 1 FF IREADY DRSEL ETCH CUT READY STATUS TO USER CONTROLLER Figure 1 8 Radial Ready Installation Note MC1 through MC4 cannot be used as radial motor control when using this option 1 19 7 Ready Modified RM This option allows the drive to write on the upper surface of a single sided diskette It prevents the drive from making Ready become false when the upper surface of a single sided diskete is selected To implement this option connect a jumper at the RM pads 1 19 8 Radial Index RI This option uses the alternate 1 0 lines for radial index lines This option allows the user to monitor the index of each drive independent of drive select This option cannot be used concurrently with radial ready or with independent motor control Radial Index is implemented by removing the shunt bridge at U3 Pins 6 and 11 by etch cutting radial index and by
76. ty double sided drive 0 6 MBytes single density double sided drive 1 2 MBytes double density double sided drive FM single density MFM double density CURRENT AMPS CURRENT AMPS TABLE 1 2 POWER REQUIREMENTS 1 5 Volts 0 70 Amps typical 2 24 Volts After motor start interval Spindle Motor 0 35 Amps typical Stepper Motor 0 40 Amps typical Electronics Q 17 Amps typical Total 0 92 Amps typical 3 24 Volts During motor start interval a Configured for stepper motor enabled during motor start 2 5 Amps typical surge 2 5 2 0 100 200 300 400 500 600 TIME MILLISECONDS D Configured for stepper motor disabled until motor comes up to speed 2 1 Amps typical surge TIME MILLISECONDS 1 4 A Inspect the shipping package for obvious damage B Open the shipping and remove the drive C Inspect the drive s overall appearance Ensure that there are scratches on the bezel D Ensure that all internal connectors are seated properly E Turn the diskette lever counterclockwise and remove the shipping diskette F Insert a blank diskette close and then open the diskette lever The diskette should eject G Insert a blank diskette and manually turn the spindle pulley It should rotate freely The dynamic incoming inspection procedures include Connectthe drive to an exerciser or computer tester capable of seeking writing and reading B Power up the test equipment and apply
77. ust remain stable in the true low state until the execution if a Step or Read Write command is completed 1 17 3 Program Shunt The program shunt is AMP Part Number 435704 8 The program shunt positions are programmed by cutting the particular shunt The program shunt is installed in a dip socket At the user s option the program shunt may be removed and replaced by a dip switch Pins 8 and 9 of the program shunt are not used See Table 1 5 for listing of the program shunts 1 14 GL L Jun 52 999 51 D 3 ALTERNATE TEST POINT INDEX TRIGGERING R33 9 MC4 RP1 DS1 9 WP P13 TP11 TP12 P2 P3 P10 P1 P11P12 Figure 1 6 Circuit Board Assembly D C POWER MOTOR OFF L DRIVE SELECT OUTPUTS VALID DIRECTION SELEGT STEP SIDE SELECT WRITE GATE WRITE DATA VALI READ DATA SSS 0 8 SEC MAXIMUM 500 NSEC MINIMUM 1 USEC MINIMUM 1 USEC MINIMUM 1 USEC MINIMUM 3 MILLISECONDS MINIMUM 100 NSEC MINIMUM 4 USEC MAXIMUM EN 18 MSEC MINIMUM 100 USEC MAXIMUM 550 USEC MINIMUM Figure 1 7 General Control and Data Timing Requirements 1 16 1 18 DS AND HL POWER SAVE OPTIONS The drive is set up with the HL option in This stepper power from head load line option supplies power to the stepper motor when the head load line goes low true which results in lower stand by current consumption shipped
78. ut lines 1 Write Current Switch 2 Write Data 3 Write Gate 4 Side Select TM848 2 only 5 Direction 6 Step 7 Head Load These input lines are individually terminated through a 150 ohm resistor pack that is installed in the dip socket located at integrated circuit location RP1 In a single drive system this resistor pack should be installed to provide the proper terminations In a multiple drive system only the last drive on the interface is to be terminated All other drives on the interface must have the resistor pack removed see Figure 1 6 1 17 2 Drive Select The Select lines provide a means of selecting and deselecting a drive These four lines 051 through DS4 allow independent selection of up to four drives attached to the controller When the signal logic level is true low the drive electronics are activated and the drive is conditioned to respond to Step orto Read Write commands When the signal logic level is false high the input control lines and the output status lines are disabled The drive select address is determined by a movable shorting plug installed on the circuit board Select lines one through four provide a means of daisy chaining a maximum of four drives to a controller Only one line can be true low ata time An undefined operation might result if two or more units are assigned the same address or if two or more select lines are in the true low state simultaneously see Figure 1 7 A select line m
79. ve action Figure 2 10 Head Azimuth of Acceptable Lower Limits F Figure 2 11 depicts an alignment of exactly plus 9 12 or 18 minutes depending upon the manufacturer of the diskette used Bursts 3 and 4 are of equal amplitude This is the upper limit of allowable azimuth error If this signal is observed the Cats Eye alignment should be checked prior to any corrective action G After the lower head has been checked switch to read on the upper head and observe the azimuth pattern Both the upper and lower heads should be within the specification 2 8 Figure 2 11 Head Azimuth Alignment of Acceptable Upper Limits Note The head s azimuth is not adjustable It is suggested that the drive be sent to an authorized repair center or a new Head assembly be installed In the latter case all previous adjustments should be made again LOAD ARM ADJUSTMENT This adjustment is made to ensure proper loading of the head when the diskette is engaged see Figure 2 12 A Insert a work diskette into the drive B C Turn the diskette lever to load the disk and seek to Track OO There should be a space of 015 inch minimum between the head load arm and the load plate Seek to Track 76 and ensure that a space of 015 inch minimum remains between the head load arm and the load arm Adjust the screw located behind the head load cam until the foam just touches the platen Insert a work diskette and ensure that there is adequate sp
80. ve plug connectors P8 and P9 from the circuit board Cut the tie wraps that hold the head cables to the chassis Remove the clip that holds the head cables to the head cable flexure bracket m o O gt Remove the four mounting screws that attach the carriage shaft to the chassis see Figure 5 23 MOUNTING SCREWS 4 PLACES Figure 5 23 Head Carriage Removal F Lift out the Head Carriage Assembly 5 18 2 Installation A Install the carriage shaft in the carriage B Using the four original mounting screws attach the carriage shaft to the chassis C Install the Stepper Motor Assembly see Section 5 17 2 Note Take care not to damage the Arm Spring Assembly D Plug connectors P8 and P9 into the circuit board E Cable harness the Head Carriage Assembly s wires to the main wire bundle 5 18 3 Checks A Check the azimuth see Section 11 B Check the Cats Eye alignment see Section 11 C Check the index alignment see Section II 5 20 APPENDIX I PRINTED CIRCUIT BOARD SCHEMATICS AND ASSEMBLY DRAWINGS ALL CAPACITORS ARE N MICROFARADS SOV 7 ALL INDUCTORS ARE MICROHENRY S t 10 ALL RESISTORS ARE IN OHMS 4W 5 5 0 SIRAP OPTION On STRAP OPTION LOCATED IN SHUNT 02 3 3 RESISTOR LOCATED IN RESISTOR PACK RPI O gt ON UNLESS OTHERWISE SPECIFIED 9 gt SIRAP PRE ETCH ON CIRCUIT BORD ATK Dwv pr
81. wer Selected Motor On Deselected Spindle Motor Start Current Surge ENVIRONMENTAL Operating Temperature Storage Temperature Wet Bulb Temperature Noncondensing Operating Humidity RELIABILITY MTBF MTTR Error Rates Soft Read Hard Read Seek Errors PERFORMANCE Head Wear Guarantee Number of Tracks Track To Track Access Time Head Settling Time Average Access Time including head settling time Motor Start Time Disk Rotational Speed Instantaneous Speed Variation Flux Changes Per Inch Inside Track Transfer Rates Unformatted Recording Capacity IBM Format Recording Capacity Recording Method 1 3 Length 13 125 inches behind front panel Weight 5 5 pounds 5 volts 5 percent 0 75 amp typical 24 volts 10 percent 0 75 amp typical 0 20 amp typical 0 40 amp typical 2 5 amps 400 msec on 24 volts total 4 4 C to 46 C 40 F to 115 F 40 C to 71 C 40 F to 160 F 26 C 78 F maximum 20 to 80 percent 10 000 power on hours 30 minutes 1 in 10 bits 1 in 10 bits 1 in 10 seeks 15 000 media hours 77 for TM848 1 154 for TM848 2 77 per surface 3 milliseconds 15 milliseconds 91 milliseconds 700 milliseconds 360 RPM 1 0 percent 6536 FCI Side 0 both models 6818 FCI Side 1 TM848 2 only 250K BPS single density 500K BPS double density 0 8 MBytes per disk single density double sided drive 1 6 MBytes per disk double densi
82. with the exception of azimuth which must be triggered off of R33 see Figure 2 1 ALTERNATE TEST POINT INDEX TRIGGERING R33 4 Su EM DE DS2 WP TP11 o syre12 50 P2 P3 P10 P1 P11P12 Figure 2 1 Circuit Board Assembly F Adjust R133 until a reading of 166 667 milliseconds is achieved from leading edge to leading edge of the index pulses G If the drive motors speed cannot be adjusted see Section IV Troubleshooting Guide 2 2 CATS EYE ALIGNMENT CHECK AND ADJUSTMENT The Cats Eye C E alignment procedure locates the read write head at the proper radial distance from the hub center line ensuring that the track location is accurate seeFigure 2 2 This adjustment is necessary only after servicing or if diskette interchange problems are suspected 2 2 HUB CENTER LINE TRACK 0 TRACK 38 TRACK 76 Figure 2 2 Hub Center Line and Track Locations 2 3 2 2 1 OQ m m o o Cats Eye Alignment Check Set up an oscilloscope as follows Channel A Test Point 2 alternate is Test Point 4 on R30 Channel B Test Point 3 alternate is Test Point 5 on R29 Ground Test Point 1 Read Differentially A plus B B inverted Time Base 20 milliseconds per division External Trigger Test Point 11 negative trigger for single sided drives Test Point 12 negative trigger for double sided drives R33 end closest to 052 negative trigger is an alternate test point for both single

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