SERVICE MANUAL
Contents
1. TEMS LIST FOR ORIC PCB ASSY 48K ITEM DESCRIPTION ory PART NO REMARKS BATCH QT D1 IN4148 10 SC0002 XTAL1 XTAL 12MHz ih XT0008 PCB Mounted XTAL2 XTAL 8 8672375 MHz 1 XT0003 PCB Mounted RP 1 SIL Resister Pack 8 Pin 2K2 1 RE8005 7 resistors RP2 SIL Resister Pack 8 Pin 220R 1 RE8006 4 resistors RP3 SIL Resister Pack 8 Pin 10K 1 RE8005 4 resistors Resistor CR25 10R 1 REO100 5 R2 Resistor CR25 4K7 1 RE0472 5 R2 Resistor CR25 4K7 1 RE0472 5 R4 R7 R9 R10 R11 R13 R13 Resistor CR 1K 9 RE0102 5 R16 R20 R21 R5 R23 Resistor CR25 10K 2 REO103 53 R12 Resistor CR25 22K 1 RE223 5 R15 Resistor CR25 62K 1 RE9007 2 R26 R17 Resistor CR25 2K2 2 RE0222 5 ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC 1 16K PCB ASSY N Sla teg PART NO SHEET NO HED A z L m o A Ee Z o olo lea BN0135 3 of 6 ajajan S cdi ON 1982 62 63 TEMS LIST FOR ORIC 1 16K PCB ASSEMBLY ITEM DESCRIPTION QTY PART NO REMARKS BATCH QT R18 Resistor CR25 3K9 2 REO392 5 R19 Resistor CR25 8K2 1 RE0822 5 R3 Resistor CR25 470R T REO471 5 R22 R24 Resistor CR25 47K 3 RF0473 5 R25 R6 Resistor CR25 220K 1 RF0224 5 R8 Resistor CR25 100K 1 REO104 5 RV1 Skeleton Preset Resistor 220R 1 RE7221 Ci Capacitor Elec 220uF 10V 1 cA0018 C2 N C6 C72. 1E23 XT2 IC24 and IC25 provide two 4 43 MHz sample clocks in phase quadrature and the ULA provides the RGB signals plus the synch pulse Sampling of the RGB signals takes place at a rate of 8 86 MHz in the ROM 1C23 whose binary output drives a ladder type D to A converter providing a composite analogue video signal This is fed via the UHF modulator to the television output socket Printer interface Port A of IC6 6522 is multiplexed between th sound circuit 1C4 and the printer port Printer strobe and acknowledge signals are provided by PB4 and CA1 respectively Data at port A is therefore directed to the printer of IC4 depending on which control lines are active 20 4 TEST EQUIPMENT There is no requirement for any specialized test equipment however W recommend you have an oscilloscope capable of dealing with up to 25 MHZ and a tonerneter for PCB work 21 S FAULT FINDING Introduction Since the ORIC 1 was first launched one or two modifications to the circuit have been implemented at various times The circuit diagram and parts list reflects Issue 4 of the circuit however it is possible that if you receive an early model to repair there may be some slight circuit differences between it and the circuit diagram and or parts list Do not confuse PCB issue number with circuit issue
3. C9 A11 C9 through C13 C13 C34 Capacitor Cer Disc 47nF 13 CA1001 0 2 Pitch C20 C22 C23 C35 E19 Capacitor Cerm Plate 2n2 1 CA2009 Mullard 630 06222 ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC 1 16K PCB ASSY E 3 gt 9 E a PART NO SHEET NO a E E S BN0135 4 of 6 v Q aa A 1982 TEMS LIST FOR ORIC 1 16K PCB ASSEMBLY ITEM DESCRIPTION QTY PART NO REMARKS BATCH QT C3 Capacitor Tant 10uF 6V3 1 CA4008 0 2 Pitch C4 Capacitor Tant 2u2 25V iL CA4010 0 2 Pitch C5 Capacitor Cer Plate 10n 1 CA2002 0 24 Pitch C8 Capacitor Elec 100uF 10V 1 CA4009 Radial 0 2 Pitch C21 Capacitor Elec luF 10V 1 CA4012 Radial 0 2 Pitch C25 Capacitor Cer Disc 100n 2 CA3013 0 4 2 Pitch C28 Connected direct C29 Capacitor Tant 33u 6V3 1 CA4007 F modulator C26 N Capacitor Cer Plate 120pF 2 CA2006 0 2 Pitch C31 C32 N Capacitor Cer Plate 100pF 2 CA2003 5 0 2 Pitch C33 CV1 Capacitor Variable 2 22pF 1 CA9001 Mullard 808 11229 RL1 Relay OKI RRD51A05 1 RL0005 5VDC without diode SW1 Switch Momentary 1 SWOOO1T Reset SK1 5Pin DIN Socket PCB Mounting 1 SK0016 SK2 7Pin DIN Socket PCB Mounting 1 SK0024 SK3 Jack Socket 2 5mm 1 SK0037 ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC 1 16K PCB ASSY E Si D M PART NO SHEET NO a HIS ISS B
4. points to ICI or its pin connections being faulty It s possible that IC6 on the main PCB is faulty but unlikely A faulty column of keys is likely to be due to a bad connection on PL3 which connects with the sound circuit or the sound circuit itself IC4 One or more faulty keys not all in one particular column or row is due either to faulty key switching mechanism s or soldered connections of keys to keyboard If a key or keys start to give the wrong characters on the screen this can be due to short circuits column and row on the keyboard PCB or ICs 4 or 6 on the main PCB 32 The following are keyboard interface waveforms monitored at PL3 Pins 2 3 4 dy 9 LL 12 ims Pressing any key causes the relevant column pin to go to 0 volts except for pin 1 which goes to 4 5 volts 33 Pins 6 7 and 8 3 bit binary count 5v etc Ov TE ecc Ov Sy Tu mama n lt Pressing a key causes the lines to go to 5 volts dc Pin 13 is 2 volts dc when a key is pressed it goes to 5 volts 34 Powering up initialization faults If after powering up the screen is covered with black horizontal bars or random patterns this indicates that the contents of the ROM language interpreter and operating system have not been correctly loaded into DRAM One thing to check is that modification 63b on IC21 has been implemented If n
5. 8912 1 IC0067 G I ECS IC 6502A d IC0066 IC6 IC 6522A 1 IC0049 Le ULA ORIC 1 1 IC0069 HCS10017 IC8 N ICSN74LS257A 2 IC9257 IC20 ECZL N ICSN74LS04 2 1C9004 IC25 4 IC22 IC SN74LS365 1 1C9365 1023 IC TBP24S10 d IC0071 256x4 PROM 1C24 N IC SN74LS74 2 1C9074 IC27 IC26 IC SN74LS123 il 1C9123 IC9 IC 23128 BC184C 1 1C0072 See note on options BN01333 TR1 TR2 Transister BC184C 3 SC4001 TR3 ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC PCB ASSY 48K m e PART NO SHEET NO 2 3 8 82g 8 E S S lt BN0130 2 of 8 q a A a ol m m E a 1982 53 TEMS LIST FOR ORIC PCB ASSY 48K ITEM DESCRIPTION ory PART NO REMARKS BATCH QT D1 Diode IN4148 1 SC0002 XTAL1 XTAL 12MHz 1 XT0008 PCB Mounted XTAL2 XTAL 8 8672375MHz 1 XT0003 PCB Mounted RP 1 S I L Resister Pack 8 Pin 2K2 1 RE8005 7 resistors RP2 S I L Resister Pack 8 Pin 220R 1 RE8006 4 resistors RP3 S I L Resister Pack 8 Pin 10K 1 RE8005 4 resistors R3 Resistor CR25 470R 1 RE0471 5 R2 Resistor CR25 4K7 1 RE0472 5 R3 Resistor CR25 220K 1 RE0224 5 R11 R16 R4 R7 R9 R10 Resistor CR 1K 9 RE0102 5 R13 R20 R21 ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC PCB ASSY 48K N a 12 Sv Ills 3 de PART NO SHEET NO D A LO N x LO L a VO bou a E 00 A Z m a 00 a oo melo S S S
6. ICS if not apply the same technique to IC7 ICH IC20 IC 9 and or IC 10 11 If a line is significantly high and the computer is left switched on it will be necessary to change one or more of IC5 IC7 IC9 or ICIO as damage will almost certainly have occurred 36 In the event that no signals are present on any data or address bus lines First check the 5 volt line and if low voltage use a tone meter to locate the short or partial short Next check the 12 MHZ clock from XT1 to IC7 if the signal is not present cut the connection at IC7 and check again if the clock returns change IC7 otherwise the fault is probabiy IC 21 or XTI Finally there maybe instances where all the address and data bus lines appear satisfactory and yet there is a fault The next course of action is to introduce a fault by shorting two address lines together so that initialization cannot take place then check the data bus again and it is possible a fault may show up 37 Tape cassette loading faults The procedure for checking cassette loading is as follows 18e Insert a long cassette one which takes a few minutes to load and load it 2 Monitor the signal at IC3 pin 2 input from the cassette You won t be able to distinguish individual signals but the arnplitude should be at least 100 m volts peak to peak The
7. SI IS jld Z BN0130 3 of 8 H a A N N N P a AS Se w w A N LO m E A N wo A 1982 54 TEMS LIST FOR ORIC PCB ASSY 48K ITEM DESCRIPTION QTY PART NO REMARKS BATCH QT R5 N Resistor CR25 10K 2 RE0103 5 R23 R8 Resistor CR25 100K 1 REO104 5 R12 Resistor CR25 22K 1 RF0223 5 R15 Resistor CR25 62R 1 RE9007 2 R30 Resistor CR25 220R d RF0221 R17 Resistor CR25 4K7 2 REO222 55 R26 R18 Resistor CR25 3K9 1 REO392 5 R19 Resistor CR25 8K2 1 REO822 5 R22 R2 4 Resistor CR25 47K 3 REO473 5 R25 R29 Resistor CR25 12K 1 REO123 R31 Resistor CR25 560R 1 REO561 ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC PCB ASSY 48K m o R D o PART NO SHEET NO ole se JEMEN E e Ss e TEMP NE JE BN0130 4 of 8 A a m a a n E a 1982 55 TEMS LIST FOR ORIC PCB ASSY 48K ITEM DESCRIPTION QTY PART NO REMARKS BATCH QT RV1 Skeleton Preset Resistor 220R 1 RE7221 C2 C6 C7 C9 Capacitor Ceramic Disc 467n 18 CA1001 0 2 pitch C18 includes C9 to C18 C20 C22 C23 C34 C35 C3 Capacitor Tantalum 10uF 6V3 1 CA4008 0 2 Pitch C4 Capacitor Tantalum 2u2 25V 1 CA4010 0 27 P3tel ORIC PRODUCTS INTERNATIONAL LTD
8. generated by the expansion device It s purpose is to modify operation of the internal ROM and pRAM S to ensure unimpeded operation of the expansion device A signal generated by the expansion device to disenabl th internal ROM and thus prevent it using the data bus 12 RESET Input An externally generated power up type reset signal 02 Output Timing signal R W Output Read or Write The output signals are utilized from existing internally generated signals used for non expanded I O operation The I O works in the following way Whenever the 6502 generates an address in the range 0300 to O3FF the ULA detects it and generates a signal which as CS is used to enable the interface adapter IC6 and as I O is fed to the expansion part PL2 Provided the address is in the range 0300 to 030F IC6 is enabled and the keyboard or printer interface ports are used If however the address falls in the range 030F to O3FF the external device connected to PL2 should generate I O CONTROL to inhibit the interface adapter IC6 thus leaving the data bus free for the expansion port 13 All ORIC designed peripherals for use on the expansion port have addresses from 0300 upwards All non ORIC designed peripherals should have addresses at or below O3FF this way there is the least likelihood of a conflict of addresses The signa
9. on a television set the RGB signals to IC23 and 1C22 must be correct so check the video encoder and output chain as follows Check the modulator signal input with an oscilloscope on the middle of the three connections at an end of the modulator casing The signals won t make much sense but you should see a peak to peak amplitude of about 0 2 volts about a dc level of OV If these signals are present change the modulator after first checking its 5 volt power supply otherwis check the outputs and inputs of IC23 follows 27 Pin 7 sync ov This signal could be pulled low if IC23 IC26 or IC27 are faulty Pin 1 as for pin 7 but phase shifted If not present replace IC23 then IC26 Pin 15 If not present replace 1C23 then IC27 Pins 5 and 6 Oscillator output of 2 volts peak to peak about Ov dc 28 Another fault you may see is horizontal block bars moving up and down the screen This is usually due to faulty DRAMS but it can also be due to the 5 volt line having excessive ripple a typically faulty line shows 30 mv peak to peak To locate the faulty DRAM monitor the 5 volt line and cut the VCC pin of each DRAM in turn starting with 1C13 You will also find that often more than one DRAM is faulty and that the faulty ones get quite hot this can be checked before you start cutting pins
10. output of IC3 pin 7 should look something like Ethos 2 tiv S Check the input to IC6 pin 18 the pulses should be similar to those at IC3 pin 7 but from O volts to 5 volts If these signals are present the likely problem is IC6 38 In the vast majority of cases there is nothing wrong with the ORIC it is nearly always a case of finding the correct playback level and using good quality tape Cassette recorder heads must be clean and in general the recorder must be in good condition Try not to use batteries as these generally produce a slightly different tape speed and as a result the frequency of the tones change Another course to watch for is a damaged pinch wheel Sometimes if the recorder is unpowered and the PLAY button is left depressed for an extended period of time a lump can be impressed on the pinch wheel by the capstan and this will produce a slight perturbation in tap speed very revolution of the pinch wheel 39 IC4 Waveforms Pins 7 to 13 I 5V Bue OV BV Pin 14 OV k Bv Pin 18 OV O 5 ms Pin 20 700 ms Pin 21 Pin 22 E Bee eel Pin 24 Pin 25 26 27 When a key is pressed pins 21 28 go to OV pin 20 goes to 4 5V A ESC aio D PR A ue MEE MMC MBA Tr AA A AA AA NAK A AE IC5 Waveforms Pin 3 i li 5V Pin 37 Li 6 3 zs Ov Pin 39 4 Sv 03 Ov s vs Pins 1 21 OV Pin 4 IRQ OV Pin
11. 40 RST TC EV Pin 6 NMI lip 5V Pin 34 R W L 5V lus Ov This puise will not be stable so trigger the scope timebase internally from the channel you are using to monitor the waveform 41 IC6 Waveforms 4 5V Pin 34 RST TE RAF EECH li 5v Pin 21 IRQ w we a OV Pin 35 38 RS0 3 T 3 5V Pin 22 R W As For IC5 pin 34 5y Pin 21 T 25 oy os loms LESV Pin 24 CS Pin 40 ov Pin 18 Tp SV 42 IC7 Waveforms k sa U Pin 7 Clock OV 64 ys Pin 16 E 4 5v Synch OV 4us Pins 19 20 21 5v Video ov Pin 27 R W AS PER ICG PIN 22 Pin 14 4 i e 257 66 43 6 ORDERING COMPONENTS AND RETURNING FAULTY ITEMS All parts components either for modification or repair can be obtained by order in the usual way from ORIC PRODUCTS INTERNATIONAL SALES DEPARTMENT COWORTH PARK LONDON ROAD ASCOT BERKS SL5 7SE The components are shipped direct from the manufacturing plant All faulty items requiring service should be sent together with details of the fault to ORIC MANUFACTURING UNIT 11 HAMPTON FARM INDUSTRIAL ESTATE HAMPTON ROAD HANWORTH MIDDLESEX Addresses no longer valid SDM 44 We ask that you supply as many details as possible regarding defective items in order that the it
12. 502 In the ORIC 1 16K machine the same processor is used which can address up to 64K locations The top 16K as before is used to access ROM and the remaining bottom 48K for DRAM However since there is only 16K of DRAM available the top two address bits A14 and A15 are ignored and the bottom fourteen bits only are used to address a maximum of 16K I O and Expansion The ORIC 1 48K and ATMOS both have a built in capability to expand the I O to include extra hardware which can be ither peripherals or memory ROM or RAM For this purpose an expansion port in the form of PL2 gives access to the address and data bus lines In addition there are a number of signals som generated by the microcomputer and som generated by the expansion device which are necessary for expanded I O operation these signals are as follows 11 I O Output I O Control MAP Input ROMDIS Input This is generated by the ULA whenever th 6502 addresses locations in the range 300 to 3FF 1 O It is used internally by IC6 as well as being available at PL2 expansion socket This should b generated by the expansion device Input connected to PL2 Tt s purpose is to inhibit IC6 and thus prevent the keyboard and printer ports being interfaced with the data bus whilst the expansion device is being addressed This should b
13. B for monitoring purposes You will notice that the ribbon cable used on the ATMOS has a different coloured wire at one end this is to identify pin 1 of the socket SO you don t connect it the wrong way round To remove the main PCB unscrew the two screws and unplug the keyboard connection 25 Screen faults By screen faults we mean those associated with the video encoder circuits IC23 to IC27 XT2 and the modulator and the RGB monitor output circuit 1C22 A common fault is the absence of any data at all on the screen there are other screen faults resulting in incorrect characters patterns or rubbish however these are usually due to other faults and are covered later in the chapter The first thing to do is find out if the fault occurs on a video monitor an ordinary television or both If the fault is on the video RGB monitor and the television check with an oscilloscope the RGB signals on pins 19 20 and 21 of IC7 which should each show square pulses from 1 volt to 1 volt If these signals are not present try replacing first IC7 and then IC23 both of which are plug in if the fault remains replace IC22 The only other possibility is processor IC5 it s usually IC7 26 If the fault is only on the RGB video monitor the most likely causes are IC22 and video output socket SKl and resistor pack RP2 If the fault is only
14. ICI 8 Insulator 1 MTO127 LCE 9 Screw M3x8LG PAN HD POZI d FS3081 TEL 10 Washer M3 Shakeproof 1 FW0103 ICI T Nut M3 1 FN0003 DT 13 20 SWG Tinned Cu Wire A R WR0009 LK 15 Solder 65 35 Tin Lead A R MC0043 ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC 1 16K PCB ASSY e PART NO SHEET NO El EB m a ge ca BN0135 1 of 6 HI A 1982 60 TEMS LIST FOR ORIC 1 16K PCB ASSEMBLY ITEM DESCRIPTION QTY PART NO REMARKS BATCH QT ICI Voltage Reg 7905 1 SC2008 TO 220 Plastic IC2 LM386 1 IC0068 EES LM358 IC0004 IC4 AY 3 8912 dl IC0067 IC5 R6502AP 1 IC0066 IC6 R6522AP 1 IC0049 IC7 HCS10017 1 IC0069 IC8 N SN74LS257A 2 IC9257 IC20 IC21 must be IC21 N SN74LS04 2 IC9004 National TC25 7 IC22 IC SN74LS365 1 IC9365 IC23 IC TBP24S10 al IC0071 Programmed IC24 N IC SN74LS74 2 IC9074 ELT 7 IC26 SN74LS123 dE IC9123 Hitachi See note ICO 23128 BC184C 1 IC0072 BN01333 on options IC12 N TMS4416 15NL RAM 2 IC0070 Texas IC19 TRI TR2 Transister BC184C 3 SC4001 TR3 ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC 1 16K PCB ASSY e PART NO SHEET NO A E BN0135 2 of 6 HI A 1982 61
15. If the quality of the picture deteriorates this can be due either to poor colour or sound on vision For poor colour first try the re tuning procedure which is detailed on page 4 of the ORIC ATMOS MANUAL If this does not solve the problem the fault probably lies with variable capacitor CVI or the associated components of 1C25 Check also that the three RGB signals to IC23 pins 2 3 and 4 are approximately the same amplitude for sound on vision faults RV1 or the RC network between th output from 1C4 and the Input to IC2 are likely causes 29 Picture quality adjustment There are two adjustments which affect the signal out of the UHF modulator RV1 controls the bias on the composite video signal feed into the UHF modulator If RVI is incorrectly set in one direction sync pulses are compressed causing the picture to jump out of line hold and frame hold if incorrectly set in the other direction compression of the video takes place causing yellows to turn white The best way to adjust is to use the yellow PAPER and adjust RVI until it just starts to turn white The other adjustment is the frequency of the colour subcarrier control led by CVI First and foremost it must be within a small tolerance of the correct frequency of 4 43361875 MHz Also important is its relationship with the video line frequency which itself is derived from 12 MHz clock
16. If the relationship is incorrect or too far out then colour fringing occurs on vertical boundaries and on text This adjustment should be made when the ORIC has reached its normal working temperature the correct position being the one that gives the best colour picture 30 Sound faults A common fault is Lthe absence of any sound and before doing anything else check the loudspeaker and the connections to it from the sound power amplifier IC2 Next type in a short routine to generate continuous sounds 1 ZAP 2 GO TO 1 3 RETURN Using the oscilloscope check IC4 pins 1 4 5 you should see positive going square pulses from Ov to about 800 mv amiplitude If there signals are absent the fault is likely to be the sound circuit ICA or IC6 Next check IC2 pin 3 the pulses should be about Imv above OV and pin 5 where the signals should be 1 5 volts peak to peak about a dc level of 2 5 volts Finally check the speaker terminal which is the same as IC2 pin 5 with a dc level of 0 volts 3l Keyboard faults If a number of keys fail to function correctly first refer to the keyboard PCB circuit diagram and check if the problem keys make up a complete row or a complete column the circuit diagram show clearly how the keys are arranged electrically into columns and rows A faulty row of keys producing no characters or intermittent characters
17. N HD POZI ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC 48k ii o PART NO SHEET NO 2 af gt a A A e S BN0127 1 of 2 vi N 1982 TEMS LIST FOR ORIC 48K ITEM DESCRIPTION QTY PART NO REMARKS BATCH QTY Aerial Lead 2M 1 LA0015 RCA Phono to 75ohm Co axial shrink rap or poly bag Mains Adaptor 1 MT0046 240 50Hz to 9V 600Ma Unreg 13A plug to 2 5mm Female Jack Lead Assy 3 pin DIN 3 Pin DIN 1 LA0016 Cassette User Manual 1 MN0020 Guarantee Card 1 MN5001 Polystyrene Pack 1 PK0002 2 Pieces Cardboard Sleeve Inner 1 PK0001 Cardboard Sleeve Outer 1 PK0003 Polythene Bag 13 x 8 1 MC0047 ORIC Welcome Cassette 1 DK5001 Oric User Magazine 1 MN1001 Supplied in Polythene Bags ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC 48k a TE PART NO SHEET NO EE G a S BNO127 LE 2 a N 1982 48 TEMS LIST FOR ORIC 16K ITEM DESCRIPTION QTY PART NO REMARKS BATCH QTY Top Cover 1 MT0117 57 Piece Key Set 1 MT0118 Keyboard Label 1 MT0119 Logo Label 1 MT0120 Serial No Label 1 MTO126 Switch Membrane 1 MTO121 Oric Keyboard PCB Assy 1 BN0129 Screw No 4 Self Tap x 4 LG 10 FS9002 PAN HD POZI Screw No 4 Self T
18. N QTY PART NO REMARKS BATCH QT RCA Phono to Aerial Lead 2M 1 LA0015 75 Ohm Co axial Shrink rap or poly bag 240 50Hz to Mains Adaptor 1 MC0046 9V 600Ma Unreg 13A plug to 2 5mm Female Jack Lead Assy 3 Pin DIN 3 Pin DIN 1 LA0016 Cassette Users Manual Atmos 48K 1 MN0021 Guarentee Card ik MN5001 Polystyrene Pack 1 PK0005 2 Pieces Cardboard Sleeve Inner 1 PK0004 Cardboard Sleeve Outer 1 PK0003 Polythene Bag 13 x 18 1 MC0047 OFIC Welcome Cassette 1 DK5001 Oric User Magazine 1 MN1001 Supplied in Polythene Bags ORIC PRODUCTS INTERNATIONAL LTD TITLE ASCOT BERKS ATMOS 48K a m PART NO SHEET NO D la a A a x Eb et BN0140 2 of 2 n 1982 67 APPENDIX 2 MODIFICATION LEAFLETS Note Where a Modification necessitates a change to the parts list the details will be given on the leaflet it is then up to you to ammend the applicable parts list 68 ORIC MODIFICATION LEAFLET MODIFICATION NUMBER 52 DATE OF ISSUE UNIT s AFFECTED MODEL MAIN PCB ISSUE CIRCUIT DIAGRAM ISSUE 1 All issues ORIC 1 2 All issues Currently issue 7 16K and 48K 3 All issues 4 Issue 2 only REASON FOR MODICFICATION Incorrect Componet positioning To improve speaker vol
19. N0135 5 of 6 A 1982 64 TEMS LIST FOR ORIC 1 16K PCB ASSEMBLY ITEM DESCRIPTION QTY PART NO REMARKS BATCH QT R N IDH 20LP PLI 20 Way IDC Plug RT Angle 1 PL0024 y 9 SR3 TG R N IDH 34LP PL2 34 Way IDC Plug RT Angle 1 PL0008 S 7 2 5R3 TG PL3 14 Way Wafer 1 PL0025 R N WTS 14S 1 T Socket DIL 28 Way 1 SK0008 LGS ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC 1 16K PCB ASSY m d Dio PART NO SHEET NO es co Z o WII OQ B ess KE BN0135 6 of 6 N cdi 1982 65 TEMS LIST FOR ATMOS 48K ITEM DESCRIPTION oTY PART NO REMARKS BATCH QT Top Cover 1 MTO140 Keyboard 1 BNO138 Label Atmos 48K 1 MTO142 Serial No Label 1 MTO126 Screw No 4 Self Tap x 4 LG 5 FS9002 PAN HD POZI Screw No 4 Self Tap x 3 8 LG 3 FS9003 PAN HD POZI Oric PCB Assy 48K 1 BN0130 Bottom Cover 1 MT0141 Feet 4 HA0038 Self Adhesive Screw No 6 Self Tap x 3 8 LG 6 FS9005 PAN HD POZI Handwritten addition Foam Pad MC0049 ORIC PRODUCTS INTERNATIONAL LTD TITLE ASCOT BERKS ATMOS 48K a m PART NO SHEET NO D la a A a x H D BN0140 1 of 2 n 1982 66 TEMS LIST FOR ATMOS 48K ITEM DESCRIPTIO
20. SERVICE MANUAL FOR THE ORIC 1 and ORIC ATMOS MICROCOMPUTERS This version typed and scanned by S D Marshall 2003 www 48katmos freeuk com AMENDMENT RECORD DATE AMENDMENT PAGES REMARKS RELEVANT ISSUED NUMBER AFFECTED MODIFICATION NUMBER OR SERVICE BULLETIN Copyright Oric Products International Limited 1984 The information contained in Lthis document must not be reproduced in any form whatsoever without prior written permission from Oric Products International Limited The product described in this document is subject to continuous development and it is acknowledged that there may be errors or omissions Oric can accept no responsibility for such omissions and or errors nor for damage or loss resulting from work carried out on the product by persons other than those authorised to do so by Oric Products International Limited Oric would be most grateful for any comments and or suggestions from users regarding this document or the product it describes All such correspondence and queries regarding this manual should be sent to Customer Services Oric Products International Limited Coworth Park London Road Ascot Berks SL5 7SE Note Oric closed down some time ago Addresses printed here are no longer valid and it is assumed this document can be regarded as copyright free SDM This document is for the use of ORIC auth
21. TITLE ORIC PCB ASSY 48K N m ta m E E PART NO SHEET NO D A O N W N L L a A Z o Z o A Zo Z o alas a ea EX q a BN0130 5 of 8 e rne oe TS C SS do A N o m o M UC M A 1982 56 TEMS LIST FOR ORIC PCB ASSY 48K ITEM DESCRIPTION QTY PART NO REMARKS BATCH QT C5 Capacitor Cer Plate 10n 1 CA2002 C8 Capacitor Elec 100uF 10V 1 CA4009 CA Capacitor Elec luF 10V 1 CA4012 Radial 0 2 P C19 Capacitor Cer Plate 2n2 1 CA2009 Mullard 630 06222 C25 N Capacitor Cer Disc 100n 2 CA1004 0 2 Pitch C8 C26 N Capacitor Cer Plate 120uF 2 CA2006 0 2 Pitch C31 C29 Capacitor Tant 33uF 6V3 1 CA4007 0 2 Pitch C32 Capacitor Cer Plate 100pf 2 CA2003 C33 ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC PCB ASSY 48K N m 2 Sg ogl Blan 59 PART NO SHEET NO D A AX AX x Zo SE hd a SA a Si SN N oo SE qe E NES to x BN0130 6 of 8 A A 1982 57 TEMS LIST FOR ORIC PCB ASSY 48K ITEM DESCRIPTION QTY PART NO REMARKS BATCH QT CVI Capacitor Variable 2 22pF 1 CA9001 Mullard 808 11229 RLI Relay 1 RL006 Alternative RL005 SWI Switch Momentary 1 SW0002 Reset PL3 Wafer 14
22. V line on the main PCB for connection to the earth clip on your oscilloscope probe The only other possibility is to use the OV side of the This sentence isn t finished SDM 23 All components on the circuit diagrams have circuit references by which they are identified on the printed circuit boards In general these references are clearly visible on the PCBs although the odd one or two are obscured by disc capacitors The waveforms for ICs 4 5 6 and 7 at the end of this section are common and therefore not associated with any other fault These and all other waveforms were monitored on a known serviceable ORIC ATMOS with no external peripherals connected 24 Disassembly The procedure is the same for both the ORIC 1 and ATMOS computers Remove the bottom part of the outer case which is secured to the top part by six screws Once this is done you will see the main printed circuit board which is secured to the keyboard printed circuit board by a screw in two of the four corners The electrical connections between the main PCB and keyboard PCB are via a 15 way connector On the ORIC 1 this is a rigid plug socket connection but on the ATMOS a ribbon cable termination in a socket is used and connects with pins on the main PCB of which pin 1 is nearest to the loudspeaker All the 15 pins protrude through to the upper side of the PC
23. Way 1 PL0026 RN WTS 14S 3 T Similar to K k k 2 1 SK0037 SK3 Jack Socket 5mm LD 0202 ITR SK1 Skt DIN 5 Way 180 Rt Angle di SK0016 Eurocomp SK2 Skt DIN 7 Way 270 Rt Angle SK20024 Eurocomp R N IDH 20LP PL1 20 W IDC pl Rt Angl 1 PLOO24 SS PS mou SR3 TG R N IDH 20LP PL2 20 W IDC pl Rt Angl 1 PL0008 e PES VUE SR3 TG Socket DIL 28 Way 1 SK0008 TES ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC PCB ASSY 48K N ma m L Bo PART NO SHEET NO Id A zo a A M gt co u OS Gar oS a e BN0130 7 of 8 EN m Q A A 1982 58 TEMS LIST FOR ORIC PCB ASSY 48K ITEM DESCRIPTION oTY PART NO REMARKS BATCH QT ECLZ N IC4164 8 IC0073 Used on 48K RAM IC19 64K D RAM 150ns Pack Units Includes all ICs 12 19 ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC PCB ASSY 48K N m Ke S PART NO SHEET NO D A gt Re al n GER Ee BN0130 8 of 8 c N 1982 59 TEMS LIST FOR Oric 1 16K PCB Assembly ITEM DESCRIPTION QTY PART NO REMARKS BATCH QTY 1 Oric 16K PCB 1 MTO123 3 Loudspeaker 25ohm 2 Dia 4 MC0005 As per sample Double sided 4 M ti Pad 1 MC0044 Su E Foam 15x5x2 5 Modulator Astec 1233 1 MC0010 vi Heatsink Redpoint TV5 1 HA0037
24. ap x 3 8 LG 3 FS9003 PAN HD POZI Self Adhesive Foam Pad 1 MC0045 PCB PCB Oric PCB Assy 16K 1 BN0135 Bottom Cover 1 MTO122 Feet 4 HA0038 Self Adhesive Screw no 6 Self Tap x 3 8 LG 6 FS9005 PAN HD POZI ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC 16k D PART NO SHEET NO 2 w A EE 3 BN0128 1 of 2 o A 1982 49 TEMS LIST FOR ORIC 16K ITEM DESCRIPTION QTY PART NO REMARKS BATCH QTY Aerial Lead 2M 1 LA0015 RCA Phono to 75ohm Co axial shrink rap or poly bag Mains Adaptor 1 MT0046 240 50Hz to 9V 600Ma Unreg 13A plug to 2 5mm Female Jack Lead Assy 3 pin DIN 3 Pin DIN 1 LA0016 Cassette User Manual 1 MN0020 Guarantee Carq 1 MN5001 Polystyrene Pack ih PK0002 2 Pieces Cardboard Sleeve Inner 1 PK0001 Cardboard Sleeve Outer 1 PK0003 Polythene Bag 13 x 8 1 MC0047 ORIC Voucher 40 Oric 1 1 MN5002 Oric User Magazine 1 MN1001 Welcome Cassett 1 DK5001 Supplied in Polythene Bags ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC 16k D E E 5 2 PART NO SHEET NO a lt o A Bs S3 BN0128 2 of 2 A 50 1982 IEMS LIST FOR ORIC KEYBOARD PCB ASSY ITEM DESCRIPTION QTY PART NO REMARKS BATCH QTY 1 Oric Keyboard PCB 1 MT0115 Dr
25. em s be returned to you in the shortest possible time 45 APPENDIX 1 PARTS LISTS The following parts lists are supplied ORIC 1 48K Main item list BN0127 ORIC 1 16K Main item list BN0128 ORIC 1 16K amp 48K Keyboard assembly BN0129 ORIC 1 48K Main PCB BN0130 ORIC 1 16K Main PCB BN0135 ATMOS Main item list BN0140 You will note there is no parts list for the ATMOS main PCB and keyboard assembly The ATMOS uses the same main PCB as the ORIC 1 48K see ATMOS main items list which calls up BN0130 main PCB The ATMOS keyboard assembly is a bought in item and the only part which can be replaced is the integrated circuit 1C1 the part number for this is in parts list BN0129 since all keyboards use the same circuit 46 TEMS LIST FOR ORIC 48K ITEM DESCRIPTION QTY PART NO REMARKS BATCH QTY Top Cover 1 MT0117 57 Piece Key Set 1 MTO118 Keyboard Label 1 MTO119 Logo Label 1 MTO120 Serial No Label 1 MTO126 Switch Membrane 1 MTO121 Oric Keyboard PCB Assy 1 BN0129 Screw No 4 Self Tap x 4 LG 10 FS9002 PAN HD POZI Screw No 4 Self Tap x 3 8 LG 3 FS9003 PAN HD POZI Self Adhesive Foam Pad 1 MCO045 PCB PCB Oric PCB Assy 48K 1 BN0130 Bottom Cover 1 MTO122 Feet 4 HA0038 Self Adhesive Screw no 6 Self Tap x 3 8 LG 6 FS9005 PA
26. erring prog rams from one Cassette to another or using bought in software In slow mode each data bit occupies a number of carrier cycles and an average is taken when loading to detect a logic 1 or 0 In this way one or two drop outs can be tolerated without affecting the average value By comparison in fast mode each data bit is represented by one cycle of the carrier consequently any droprout results in a corrupted data bit The circuitry of the cassette interface is very simple indeed For TAPE OUT the counter timers in the 6522 are used to generate the pulse stream which is attenuated by R12 and R13 to approximately 150 mv peak to peak and shaped by C7 TAPE IN also uses the counter 18 timers in the 6522 but this time to measure pulse widths IC3 is a dual op amp and converts the audio signal into a TIL signal The first stage is a unity gain inverting buffer amplifier in at pin 2 and out at pin 1 The second stage is a positive feedback amplifier providing about 50 mv of hysteresis TRI provides buffering for the 6522 IC4 and TR3 drives the remot control relay 19 PAL Encoder IC23 and 27 and UHF Modulator 1C26 provides the colour burst gate pulse which occurs soon after the synch pulse input This pulse is fed to TC23 IC27 is also triggered by synch pulses its output is divided by 2 and provides a PAL switching input to
27. ether with a checkout procedure or instructions and where necessary the relevant waveforms and voltages you would expect to find on a fully serviceable unit voltages are approximate The procedures waveforms and likely faulty components are based upon records kept by the manufacturer and as such they represent the latest information available Updated information will be issued as and when it becomes available DOCUMENTATION AMENDMENTS AND EQUIPMENT MODIFICATIONS Whenever a design modification to the existing unit is implemented by the manufactures a modification leaflet will be issued to all dealers and service centres in possession of service manuals The modification leaflet should be inserted in appendix 2 and modification components can be ordered as per instructions in Section 6 In the event that a modification to the equipment affects the service manual contents revised pages will be issued under an amendment number for insertion into the manual All such amendments should be recorded in the amendment record at the front of the manual From time to time a list of modifications and amendments currently in existence will be circulated which will enable you to check if your manual is up to date Service bulletins will also be issued from time to time with instructions for any work which can be carried out by authorised ORIC dealers Service bulletins should be i
28. he V1 1 ROM software to give a reduced width BDIR pulse ACTION TO BE TAKEN Ta Order the components in the usual way under the following part Numbers Resistor 22K Ohms RE0223 Capacitor 1 0 nf CA2004 2 Cut the track between pin 18 of ICA and pin 19 of IC6 then Fit capacitor as shown on sheet 2 Bee Fit the resistor between pin 6 and 18 of IC4 as shown on sheet 2 4 Do not ammend the parts list as this is not a production item Change affecting all models We recommend however you ammend The circuit diagram by drawing in the components and Identifying them SB1 service Bulletin number 1 Sheet 1 of 2 CE BULLETIN ORIC SERVI Number 1 ba ESA co o q o o LES NR ra b F NAN 2 E A gt SN MORAN H Dese EN i Ss I P se gt e deva dica Nn tocnseesel andhanan hw dle b Y D LD AHH H AHU qasattitt joo ay nn U d Lt ff O Pe L RK a ilm Eegenen DRAWINGS The following are supplied ORIC 1 48K main printed circuit board circuit diagram This can also be used for the ORIC 1 and the ATMOS The only difference is in the ORIC 1 16K which for the 48K models uses only two DRAMs as compared with eight ORIC ATMOS keybaord circuit diagram This can also be used for the ORIC 1 the only difference i
29. illing Drg Assy Drg 3 IC 4051B d IC0059 5 Socket 14 Way 1 SK0022 R N SBF 14 100T 7 20 SWG Tinned Copper Wire A R WR0009 300mm 9 Solder 63 37 Tin Lead A R MC0043 ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC KEYBOARD PCB ASSY N PART NO SHEET NO m n m 3 2 a BN0129 1 of 1 H A 1982 51 TEMS LIST FOR ORIC PCB ASSY 48K ITEM DESCRIPTION QTY PART NO REMARKS BATCH QTY 1 Oric PCB 1 MT0116 Drilling Drg Assy Drg 3 Loudspeaker 25ohm 2 Dia 1 MC0005 4 Mounting Pad 1 MC0044 Double sided foam 15x5x2 5 Modulator 1 MC0010 Astec 1233 Lunghwa LUM8F36 7 Heatsink Redpoint TV5 1 HA0037 ICI 8 Insulator 1 MT0127 ICI 9 Screw M3 x 8LG PAN HD POZI 1 FS3081 ECT 10 Washer M3 Shakeproof 1 FW0103 ICI 11 Nut M3 1 FNOOO3 ICI 13 20 SWG Tinned Co Wire A R WR0009 LK 15 Solder 65 35 Tin Lead A R MC0043 ORIC PRODUCTS INTERNATIONAL LTD TITLE ORIC PCB ASSY 48K 9 a PART NO SHEET NO ml a Lo e a S S S s BN0130 1 of 8 Y Tal E E H al al m N 1982 52 TEMS LIST FOR ORIC PCB ASSY 48K ITEM DESCRIPTION QTY PART NO REMARKS BATCH QT LC Voltage Reg 7905 1 SC2008 TO 220 Plastic IC2 AUDIO AMP OPTION 1 BN0147 Alternative BN0148 1C3 IC LM358 1 IC0004 IC4 IC AY3
30. inal C35 C13 It decouples the 5 volt power line and is positioned Immediately behind the power in socket Order under original part number 70 ORIC MODIFICATION LEAFLET MODIFICATION NUMBER 56 DATE OF ISSUE UNIT s AFFECTED MODEL MAIN PCB ISSU ENI CIRCUIT DIAGRAM ISSU E ORIC 1 8 All issues Currently issue 7 16K and 48K REASON FOR MODICFICATION 8 Improved Cassette Loading DETAIL OF MODIFICATION 8 a Fit a 1 0K Ohms resistor between IC6 Pin8 and 5 volts Order under part number RE0102 Circuit reference is R11 b Fit a 2 2 nano farad ceramic plate capacitor between IC6 pin 8 and 0 volts Order under part number CA209 Circuit reference is C19 Note The circuit references used were previously made redundant By modifications numbered 52 and 53 71 ORIC MODIFICATION LEAFLET MODIFICATION NUMBER 63 b part of 63 DATE OF ISSUE UNIT s AFFECTED MODEL MAIN PCB ISSU ENI CIRCUIT DIAGRAM ISSU E ORIC 1 16K and 48K 9 All issues Currently issue 7 Oric Atmos REASON FOR MODICFICATION 9 Improved Initialisation on power up DETAIL OF MODIFICATION 94 a Fit a 560 Ohms resistor between pins 7 and 24 of IC7 5 vol
31. l MAP deserves some explanation since it is this which modifies the address map for I O expansion and it works in the following way The ULA which monitors the top 8 bits of the address bus detects when the top 16K is being addressed and when the bottom 48K is being addressed If the top 16K is being addressed C000 FFFF when MAP is generated the ULA IC7 generates a signal CS which inhibits the ROM s from using the data bus In addition the entire 64K of RAM is enabled made available to the data bus This feature is used by the Microdisc drive system whose software DOS occupies the top 16K of DRAM thus ensuring that the ROM and the DOS cannot use the data bus at the same time and maintaining the 48K of DRAM for user programs If the bottom 48K is being addressed 0000 to BFFF when MAP is detected the entire 64K of DRAM is inhibited and the data bus is free to be used by 14 external memory RAM or ROM connected to PL2 MAP timing is important MAP is a 250ns pulse negative going with its leading edge occuring 80 to 100ns before the rising edge of phase 2 output from pin 39 of IC5 Circuit descriptions Power supply regulation IC1 An unregulated 9 volt supply is fed into the computer from the plug in external power unit Regulation to 5 volts is provided by ICI and associated components ICI is a negative
32. nput currents This resistor can be connected into the cassette lead of earlier machines if necessary 16 Keyboard circuitry keyboard PCB The key switches are arranged electrically in columns and rows as shown on the keyboard circuit diagram The eight rows are interrogated by ICI whose input is a 3 bit binary count and the decoded output is fed to IC6 in the computer via transistor TR2 Column decoding is via eight lines from the keyboard to the sound circuit IC4 which also acts as a keyboard I O port Gate array IC7 The gate array performs a number of functions which are a Generating synchronisation and phase pulses from the basic 12 MHz clock input b Generating timing signals for the 64K DRAMS c Address mapping and modification for I O expansion d Generating video refresh addresses decoding character and colour attributes reading data from RAM and generating the serial bit streams for the R G and B outputs 17 Cassette interface IC3 Two cassette loading and saving speeds are available fast which is 2400 baud and slow which is 300 baud Fast mode is really for the user who is saving and loading own programs using just the one cassette recorder Provided a good quality tape is used and the tape recorder is in good condition fast mode is very reliable and has the obvious advantage of speed Slow mode is more suitable when transf
33. nserted in appendix 4 Page 22 Section 5 Introduction contains some important modification information Modification leaflets service bulletins and amended additional pages can be obtained from Customer Services Oric Products International Ltd Coworth Park London Road Ascot Berks SL5 7SE Note Address invalid SDM TECHNICAL DESCRIPTION Introduction The ORIC 1 16K and 48K and ATMOS microcomputers are all designed round the 6502 microprocessor The ORIC 1 48K and the ATMOS are very similar as regards the hardware most of the differences li in the software The ORIC 1 16K uses a different PCB and it s RAM is made up of 2 x TMS4416 as compared with the 48K machine which uses 8 x MMS4164 Furthermore the 16K ORIC 1 is not suitable for use with disc drives Address Map The address map for the ORIC 1 48K and ATMOS is divided into three areas When the 6502 addresses locations C000 to FFFF the top 16K it is accessing ROM the BASIC interpreter and operating system Locations 0000 to BFFF the bottom 48K access the dynamic RAM with the exception of 0300 to 03FF whose 255 locations are reserved for INPUT OUTPUT I O page 3 of RAM 10 There is in fact a total of 64K of DRAM 48K for user programs and 16K which remains unused except for I O expansion The ROM is accessed directly from the 6
34. number as per your circuit diagram The circuit issue number changes each time the SI BOULE changes electrically The PCB issue number changes whenever physical changes are made to the board irrespective of whether or not the circuit is changed electrically Your circuit diagram indicates which modification state it reflects by quoting the last modification number called C N for change note 22 To date four modifications have been introduced which affects components on the circuit diagram Nos 52 53 and 56 and 63 The leaflets for these modifications are in Appendix 2 You will notice that the numbers of some components removed in No 52 have been reused in 53 and 56 the same applies to No 53 and 56 This practice has now ceased We recommend that for all ORIC 1 computers returned for repair you check the modification state using the modification leaf lets in Appendix 2 and modify as required to bring the computer up to the PCB Issue 4 and the latest circuit diagram issue The method of cutting through the pin of an integrated circuit is the best way of removing the load or source from a line to eliminate the IC It is quite acceptable to re solder the cut pin provide you use a heat sink to protect the circuit and easier than replacing the entire CLECUTNE We suggest that if you are going to use an oscilloscope extensively you solder a wire to the O
35. orised dealers and servicing organizations centres and is NOT for distribution to the general public CONTENTS INTRODUCTION MODIFICATIONS AND AMENDMENTS TECHNICAL DESCRIPTION TEST EQUIPMENT O1 A GO N Rp FAULT FINDING Introduction Disassembly Screen Faults Picture Quality Adjustment Sound Faults Keyboard faults Powering up initialization faults Tape Cassette loading faults Waveforms general ORDERING COMPONENTS AND RETURNING ITEMS 10 21 22 22 25 26 30 Sd 32 So 38 40 44 APPENDICES APPEN APPEN APPEN APPEN DRAWI DI DI DI DI X NGS Keyboard 1 Main printed PARTS LIST MODIFICATION LEAFLETS SERVICE BULLET circuit board NS circuit NTEGRATED CIRCUIT DATA circuit diagrams diagrams 46 68 73 74 77 78 79 1 INTRODUCTION The information contained in this manual is intended to help you in understanding the work ings of the ORIC 1 and ATMOS computers and to advise you generally on fault finding As it is impossible to include all problems we have divided the computer into a number of functional areas for the purpose of categorising faults For each functional area you will find one or more common faults listed tog
36. ot this can result in initialization faults because of the relative timing between RESET on power up becoming active and the start of clock pulse generation It is important that the clock generator circuit is working before RESET is active Next the following procedure checks initialization after power has been applied d Checking the data bus Monitor the data bus lines at the input pin 14 2 of each DRAM 1C12 to IC19 Each pin should show pulse signals of about 4 0 volts amplitude In the case of IC18 you will see additional signals of slightly greater amplitude this is an inherent design feature not a fault 35 If any line is significantly higher or lower than Lhe others check PL5 for shorts on the pins then cut the connection of the DRAM pin input and re power up If the line returns to 4 0 volt signals change the DRAM if not apply the same technique to eliminate ICS C6 C IC9 10 If all the data lines are correct check the address lines as follows Zis Checking the address bus Use the same technique as for the data lines and check lines A0 to A16 pins 9 to 25 excluding 21 of the processor IC5 You should see pulses about 4V amplitude and if any line is faulty cut the line at it s connection to the output pin of the processor If pulses appear change
37. regulator however this does not matter as the dc supply in the computer is floating ICI which is a 7905 requires 1 volt headroom Basic system clock generator XT1 provides a 12 MHz clock for the ULA IC7 from which all synchronisation and phasing signals are derived 15 System reset at power up System reset is generated by C21 and RP1 providing a very simple means of generating a power up strobe Timing here is important as the power and 12 MHz clock must be fully operational before RST becomes active For this reason it is best to reset the computer using the power connection on the rear of the ORIC as this provides a rapid build up of the 5 volt supply Using the mains switch on the wall socket provides only a slow build up of the 5 volt supply due to the large reservoir capacitor in the power pack charging up Sound 1C2 1C4 Sound is provided by ICA and a small power amplifier IC2 ICA cannot easily be directly connected to a 6502 bus and is therefore connected to port A of the 6522 IC6 Data transfers are controlled by BCl and BDIR of IC4 The current output of ICA is converted to a voltage by R4 and attenuated by R2 and R3 as the LM385 has a fixed voltage gain of 20 Later models have a 22K resistor connected between pin 3 of IC2 and GND to prevent any build up of charge on C4 due to sometimes large i
38. s that the ATMOS has an extra key labelled FUNCT sae ET O LES INT er M OT a a a e s OUI ax Caro DEL TOMATE ANITA kd rama anne Lt andetse MS L ONS DIVOBKFN Dido AG AQ pi of si gli e sl d d lt 2 O RE am EEE KG JNE BET IE SIH Er UNE e 1 a Yad ma serr gt Op O st aL af LE E di gt udin a gt 79
39. ts Order under part number RE0561 b Cut the track between IC21 pin 2 and IC7 pin 7 and insert a 220 ohms resistor Order under part number RE0221 72 APPENDIX 3 INTEGRATED CICUIT DATA Note All integrated Circuits with the exception of the following are TTL and their pin connections and other data can be found in the TEXAS TTL DATA BOOK IC3 NATIONAL SEMICONDUCTORS Cassette interfac IC4 GENERAL INSTRUMENTS Sound keyboard interface IC5 SYNERTEK Microprocessor IC6 SYNERTEK Versatile interface adaptor IC23 TEXAS MMI PROM IC9 ROM Refer to the manufacturers data book for details of these CL FCULES APPENDIX 4 SERVICE BULLETINS 74 ORIC SERVICE BULLETIN Number 1 UNIT CIRCUIT COMPONENT S AFFECTED ORIC 1 16K and 48K microcomputers Issued in February 1982 TECHNICAL BACKGROUND INFORMATION In some cases the sound circuit IC4 overheats causing a deterioration in sound quality followed by occassional faulty key operation and finally complete non operation of the keyboard The cause had Dbeen found to be pulse BDIR which is the input to pin 18 of IC4 The following actions reduces the pulse width to approximately 20 microseconds and this has proved satisfactory for all makes of sound cicuit used on the Oric l In the ATMOS the problem was eliminated by changing t
40. ume o achieve compatibility with Prestel Remove and discard C13 C19 and C39 Fit R26 between 1C22 pin and 0V order under part number RF0222 Reverse the connections to pins 19 and 21 on IC7 La 2 1 SR To support ULA test 4 1 DETAIL OF MODIFICATION 1 Dir Remove and discard R3 SF 4 Note C13 is located between IC12 and the PCB edge C19 is located between IC18 and the PCB edge C35 is located between IC6 and the PCB edge 69 ORIC MODIFICATION LEAFLET MODIFICATION NUMBER 53 DATE OF ISSUE UNIT s AFFECTED MODEL MAIN PCB ISSUE CIRCUIT DIAGRAM ISSUE ORIC 1 5 All issues Currently issue 7 16K and 48K 6 Issue 3 7 Issue 2 REASON FOR MODICFICATION Ou Components not required 6 Components not required m Components previously removed fiotted in new positions DETAIL OF MODIFICATION Ou Remove and discard the following components R11 located just above IC21 TRA located to one side of IC7 nopt speaker side C27 just above R11 6 Remove the follwing and discard R14 located between IC7 and TRA ER Fit the following components C35 This performs the same decoupling function as the C35 Removed in the modification 52 It s new position is about 13mm to the left of the original position Order under the same part number as the orig
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