Acorn Engineering News Issue 1 April 1987
Contents
1. MASTER COMPACT DISC UPGRADE INSTRUCTIONS These instructions are intended to provide information for service engineers and Acorn dealers who will be servicing the Master Compact computer No part of these instructions are to be copied or communicated to persons other than those engaged upon service work for or on behalf of Acorn Computers WARNING DANGEROUS VOLTAGES EXIST INSIDE THE CASE OF THE MONITOR STAND QUALIFIED PERSONNEL ONLY SHOULD ATTEMPT TO REPLACE PARTS COMPONENTS IN THE MONITOR STAND ENCLOSURE S IMPORTANT THE MONITOR STAND MUST BE EARTHED These instructions will be subject to change from time to time no responsibility can be accepted for any errors and or omissions Acorn Computers Ltd can accept no responsibility for any loss or damage resulting from use of the information contained herein this does not affect your statutory rights in any way The Disc Upgrade kit should include the following items 4 drive support pillars 1 double drive data cable 1 3 5 DS disc drive 4 M3 pan head screws 8 M3 shakeproof washers 1 12 month guarantee card Doc 9990011 April 1987 8 Acorn Engineering News DISMANTLING THE MONITOR STAND Turn the mains switch to the OFF 0 position and unplug the mains lead from the mains wall socket and then from the mains socket on the monitor stand Remove the 5 volt lead from the keyboard processor unit Also disconnect the disc drive data cable from the keyboard processor unit2. DO NOT DISMANTLE THE MONITOR STAND WITH THE MAINS LEAD PLUGGED IN EVEN WITH THE MAINS SWITCH IN THE O OFF POSITION THERE ARE STILL DANGEROUS VOLTAGES PRESENT Referring to figure 1 below lay the monitor stand on a flat even surface with the front of the unit facing towards you Placing your thumbs on the underside of the unit and your fingertips along the top pull the plastic front panel towards you and at the same time downwards and away from the unit Once the front panel is removed turn the unit around and remove the back panel in the same way The side panels will now pull off the unit using the same technique Plastic Side Piece c End Piece gt ee N a P A 2 A ST WSS EAA ws Plastic Side Piece Gently Prise Apart To Facilitate Remevat OF inner Assembly figure 1 Doc 9990011 April 1987 9 Acom Engineering News Having removed the front and side panels as described above turn the unit over and undo the outermost screws on the underside of the case There may be four or six screws depending on the model you have Remove the screws and washers and put them in a safe place until required again Turn the monitor stand over the right way up with the front of the unit facing towards you Slide the top backwards and pull the main unit clear taking care not to damage the disc drive data cable or the 5 volt power cable Note It may be necessary to push the side panels of the top apart slightly to al
3. 9990011 A pril1987 11 Acorn Engineering News Note Ensure that the data cable clamp is re fitted on the cable as shown above in order to prevent the cable from snaring on the underside of the disc drive Insert the screws into the clamp from the underside of the unit To hold the data cable in place plug in the IDC connector to drive 0 the existing disc drive Note that the IDC connector is polarised and will only fit onto the drive the correct way round therefore it should not be forced onto the connector Before fitting the new disc drive it has to be configured as drive 1 so that the computer recognises it Do this by positioning the switch on the side of the drive as shown in figure 4 below If the drive type you are fitting is not the same as the one described here SONY F6 3W then refer to the drive setting instructions in the Acorn Dealer Information Manual Disc Drive 5412V Cable Drive Switch Positions Support Pillar Drive 0 Drive figure 4 Take the new disc drive and fit the support pillars and washers provided in the the upgrade kit onto it Take care not to over tighten them Fit the second disc drive in place ensuring the power cable isn t trapped behind one of the support pillars Holding the disc drive and case turn the unit onto its side and align the holes on the case with the threads on the pillars Insert the screws with shakeproof washers into the pillars and tighten firmly Turn
4. for example should a fault develop in the Econet module we would expect that you should be able to repair the module to component level rather than returning the module to us for replacement The Spares department who are responsible for the return of components used in warranty repairs do not carry stocks of this board and replacements will not be issued in these circumstances This also applies to the 64k daughter board in a 128k B This would not apply in a situation where an Econet module was fitted to a Master 128 and was found to be faulty However in this case it should come back complete with the relevant manuals and cables etc as a complete product Similarly the 64k upgrade unit if supplied as a 64k upgrade kit and found faulty on arrival may be returned using the GRA procedure GRA NEW PROCEDURE We will shortly be introducing a new procedure for the return of goods for both dead on arrival DOA and warranty repair The situation for goods dead on arrival is similar to the situation that we have operated up to now but we will impose a time limit from the date of supply of the goods beyond which we will not treat the goods as DOA We shall also require you to furnish us with our reference number for the supply of the goods This number appears on both invoices and advice delivery notes For warranty repair at Central Workshop a GRA will also be issued This procedure is different from that operated in the past but allows u
5. tester B Port test software Master 128 Port test software MASTER 128 KNOWN PROBLEMS AND SOLUTIONS The following information should be regarded as being additional to the master 128 service manual Problem Loss of configuration Solution 1 Replace C11 by uu capacitor ii Replace D8 by 1N4001 ii Fit 1k8 resistor between the base and emitter of Q3 on the solder side of the PCB Problem Screen break up in MODE 7 Solution Add a 100 pF capacitor to C30 this should only be necessary for very early production machines Problem Unit crashes after a period of time Test by heating IC43 74S04 to about 55 degrees Celsius Try using a hair dryer This usually occurs on National Semiconductor chips Solution Change capacitors C85 and C86 from 100pF to 10nF Problem No colour on the composite video output Solution Connect a 470pF capacitor between the east leg of R137 amp the east leg of R153 which are located directly east of the modulator Connections should be made on the component side of the board with the leads of the 470pF capacitor being soldered directly to the leads of the two resistors N B this upgrade would not qualify for a labour refund under warranty the dealer should charge the customer or absorb the cost himself if such an upgrade is required The next issue Doc 9990011 April 1987 1 Acorn Engineering News of the Master PCB will include a switchable link to enable colour output Problem Master t
6. the unit back onto its base and connect the power and data cables to drive 1 The disc drive you have just installed in the unit Doc 9990011 A pril1987 12 Acom Engineering News Re assemble the unit by reversing the dismantling instructions given above Note Ensure that when the top case is re fitted the ventilation slots are at the back of the unit Now that the upgrade has been completed it is advisable to do a functional test of the new disc drive For example check that discs can be formatted and also that the drive will write to and read from discs without errors MASTER COMPACT SONY DISC SERVICE MANUAL The service manual for the Sony disc drive is now available from the Spares department Please note that we will not be supplying spares for this unit but probably the only simple service that can be performed on the drives is alignment Drives that fail that you are unable to service should be returned to us as complete components Please return drives to us as quickly as possible if they are within warranty as we only have a limited warranty with Sony MASTER COMPACT PHILIPS MONITORS SERVICE MANUALS The service manuals for the Philips monitors is now available from the Spares department There are two of these manuals One for the ADF32 colour monitor and one for the ADF31 monochrome monitor Please note that like the Sony disc drives we will not supply spare parts for these monitors Should you require spare parts it ma
7. 128 and diagnosis of faults can be made in the same way as with the Master 128 Some items to note It is not possible to obtain colour on the composite video output Previous methods of doing this have relied on the use of part of the circuitry for colour television modulation The Compact does not have this circuitry as there is no colour modulator The PAL TV adaptor works in a slightly different manner to the previous machines Problem Loss of configuration occurs regularly Solution Try changing R1 from 12k to 15k and C2 from 2n2 to 4n7 This modification may have been done on some machines This changes the EEPROM operating frequency from 75kHz to 35kHz allowing more time for the cells of the EEPROM to charge PORT TESTER MASTER COMPACT A port tester is now available for the Master Compact This is a Sales item and should be purchased from the Sales department This tester is the same as is used to check production machines It should be used with a Compact disc drive with two drives installed if the tests are to be fully carried out although it is possible to test units with a single drive The tester is supplied complete with Software It plugs into the joystick port and the expansion port at the side of the computer MASTER COMPACT PSU REPAIR SAFETY IMPLICATIONS As you will probably have realised the power supply to the Master Compact is in a rather different form to that found in previous BBC computers The main power
8. 2 3 mS Doc 9990011 A prill 987 15 Acorn Engineering News UNIVERSAL SECOND PROCESSOR WITH MASTER 128 The Universal Second Processor was developed primarily to permit BBC model B and B users to be able to take advantage of the Co processors available with the Master 128 ie Turbo 512 The Universal Second Processor is however capable of being used in combination with the Master 128 as well subject to the following 1 Turbo module can be contained within either the USP or the Master 128 2 512 module must ONLY be contained within the Master 128 NOT within the USP Once a module has been fitted to either the USP or Master 128 it is highly preferable for that module to remain in that location The connectors for these modules were not designed for repeated insertions and damage may occur if such swapping in and out of modules is frequent If a customer identifies that despite the above he wishes to use his USP in this way then the sockets may be replaced with ZIF sockets at the customers expense the replacement being undertaken by qualified personnel ie Acorn approved service centres MASTER ECONET MODULE NEW TYPE The Econet module ADf10 has recently undergone a small design change This includes the Collision Defect logic found on earlier BBC B network interfaces but not generally required as the protocots of Econet ensure adequate handling of network collisions in Software However some other network products do n
9. INFORMATION Acorn Engineering News PAGE CONTENTS Master 128 Service manual 1 Master 128 amp BBC B Port tester Master 128 Known problems and solutions Master Custom Chips Descriptions 4 Master Compact Spares parts availability 6 Master Compact Service information 1 Master Compact Port tester Master Compact PSU Repair safety implications Master Compact Disc upgrade instructions 8 Master Compact Sony disc service manual 13 Master Compact Philips monitors service manual Tube ULA Service information Repair of units containing modules 14 GRA New procedure Master 128 1770 DFS versions 15 Universal Second Processors with Master 128 16 ACORN ENGINEERING NEWS REF 9990011 APRIL 1987 ALL ENQUIRIES TO Acorn Computers Limited Telephone 0223 214411 Cambridge Technopark Telex 81152 ACNNMR G i 645 Newmarket Road Fax 0223 214382 w Cambridge CB5 8PB England Viewdata 0223 243642 The choice of experience SERVICE MANUAL MASTER 128 The service manual for the Master 128 is now available and can be ordered through our Spares Department The part number is 0443 004 and the price is 12 42 Being a manual this item is zero rated for VAT PORT TESTER MASTER 128 AND BBC B This product is now available There are three products The first is the Master 1B Port tester hardware The second is the software for the Master and the third is the software for the B The product codes for this are Master 28 B Port
10. RE PARTS AVAILABLE FOR THE MASTER COMPACT A full spare parts and price list for the Master Compact will be published by Acorn during April May 1987 A copy of this will be sent to all service and repair sites as soon as possible The following is a list of SAFETY CRITICAL components contained within the Master Compact monitor stand These components will only be supplied to dealers and service centres that are able to test the resulting assembly to BS 415 and BS 5850 MASTER COMPACT MONITOR STAND SAFETY CRITICAL COMPONENTS PART NO DESCRIPTION 258 100 258 101 METAL BOX 158 108 PSU 258 116 INPUT EARTH CABLE ASSEMBLY 258 117 VP FUSE CABLE ASSEMBLY 258 118 I P O P CABLE ASSEMBLY 258 119 FUSE SWITCH CABLE ASSEMBLY 258 120 FUSE 0 P CABLE ASSEMBLY 258 121 0 P SWITCH CABLE ASSEMBLY 258 124 0 P EARTH CABLE ASSEMBLY 815 900 FUSE HOLDER 5MM D PNL 815 901 FUSE HOLDER 5MM D PLSTIC BOOT 865 901 PLG MAINS 3W PNL 1E320 865 902 SKT MAINS 3W PNL IEC320 865 904 CONR INS BOOT FOR 865 902 If you have any questions relating to the supply and testing of these safety critical components please contact Alastair France on Cambridge 0223 214411 Doc 9990011 April 1987 6 Acom Engineering News MASTER COMPACT SERVICE INFORMATION The service manual for the Master Compact is now available from the Spares Department Examination of this in comparison with the Master 128 circuit diagrams will reveal that the Compact has much in common with the Master
11. ct Solution Reset the non volatile memory by holding down the R key while you switch the computer on This clears the non volatile memory and in the Compact resets the options to sensible values For the Master 128 and ET it is then worth setting sensible values using the CONFIGURE command The following are suggested CONFIGURE BAUD 4 CONFIGURE DATA 4 CONFIGURE NOBOOT CONFIGURE CAPS CONFIGURE DELAY 50 CONFIGURE NODIR CONFIGURE EXTUBE use INTUBE if an internal co proc is fitted CONFIGURE FDRIVE 0 CONFIGURE FILE 9 this is DFS vary if required CONFIGURE FLOPPY CONFIGURE IGNORE 10 Doc 9990011 April 1987 2 Acorn Engineering News CONFIGURE LANG 12 CONFIGURE MODE 7 CONFIGURE TUBE CONFIGURE LOUD CONFIGURE PRINT 1 CONFIGURE REPEAT 8 CONFIGURE SCROLL CONFIGURE TV 0 1 CONFIGURE F S 0 254 only for ET or if NET fitted CONFIGURE P S 0 235 only for ET or if NET fitted Don t reset Compacts using these CONFIGURE commands once the options have been reset they won t need it Doc 9990011 April1987 3 Acorn Engineering News MASTER CUSTOM CHIPS DESCRIPTION Keyboard Encoder CF 30047 1C16 M128 ET not used Compact This chip provides a mechanism for the processor to scan the keyboard matrix and determine the matrix position of a pressed key The actual assignment of character to key can then be done via a l
12. low the main unit to slide clear Fixing Screws i 5 12 Volt Data Cable Siot IOC Connector Connector A 5 Volt Cable S e re DC Out put Connector Li 7 NNN Fai Wiis Mains ae 4 p q ains Input Cable Clamp wy y AA A TANE Nie Fuse TRN ys Mains Auxiltiary Output Qata Cable Mains ON OFF Switch Disc Drive Pillars Keyboard Processor Connector Earth Fags Maliz input all 5 4 12Valt Conneclar ore figure 2 Doc 9990011 Aprill1 987 10 Acom Engineering News Before fitting the second disc drive it is necessary to remove the existing disc drive data cable and fit a dual disc drive cable for connection to the second drive Carefully turn the unit onto its side undo the screws holding the cable clamp in position and lift it free Unplug the IDC connector from the disc drive and untwist the cable so that it is flat all the way along Carefully pull the cable from outside the unit and thread the IDC connector through the slot in the base of the unit pulling the cable free Install the dual drive data cable along the same path used for the single drive cable just removed When the new data cable is inserted and pulled through the slot in the base of the unit it must be twisted over in order to correctly orientate the DC connectors for connection to the disc drives Refer to figure 3 below IDC Connector Data Cable Cable Clamp Fixing Screw Keyboard Processor _ Connector figure 3 Doc
13. ook up table The keyboard controller has open collector outputs that connect to the key matrix columns and inputs from the key matrix rows The device can be made to drive any of the columns and examine any of the rows In normal operation the device continuously scans all of the columns with a logic low strobe If a key is pressed then connection is made between a column and a row causing the device to address each key column in turn until it sees an interrupt Holding this column address the row inputs are examined until a logic low is seen Thus the key matrix co ordinates of the pressed key have been determined CRTC MUX CF 30048 1C31 M128 ET 1C46 Compact The prime function of this device is to multiplex the C R T addresses from the 6845 to form row and column addresses to the RAM when reading or writing video information The device also generates some control signals for the Teletext chip control of the character display period and character rounding and for the Vidproc display enable PERIPHERAL BUS CONTROLLER CF 300049 1C21 M128 ET 1C26 Compact The PBC controls the transfer of the data between the CP and the BD and ED buses The BD bus connects to peripheral chips running at 1MHz including the Teletext chip the ED bus to the tube and 1MHz bus ports The ED bus runs at 2MHz during TUBE access and at 1MHz during access to pages amp FC and amp FD 1MHz bus address space T O CONTROLLER CF 30050 1C15 M128 ET 1C22 Compac
14. ot have the facility to detect such problems adequately in software and the hardware detect logic has been re instated to allow use of Masters with these products UNIVERSAL ECONET TESTS A Universal Econet interface test program will shortly be available from the Spares Department This requires the Econet test box which was previously only suitable for use with the FIT tester A test station is also required and this should be EITHER a BBC BDE or a Master 128 with a new style Econet Module This software tests Econet interfaces on the following machine types BBC B B Master 128 ET Compact ACW The part number for this is 0343 920 Doc 9990011 A pril 1987 16 Acom Engineering News
15. ransmits to serial printer when no printer connected Solution Due to the different nature of the Master 128 serial interface and the BBC B B interface the interfaces work differently when a non working device is fitted to the interface There is no difference when a working device is connected This can be changed to match the model B and B by adding two resistors to the inputs of the RS423 input buffers These resistors should be connected from IC51 pin 8 to 5v and IC51 pin 6 to Sv IC50 pin 8 is a suitable source of 5v N B this upgrade would not qualify for a labour refund under warranty the dealer should charge the customer or absorb the cost himself if such an upgrade is required The next issue of the Master PCB will include a modification which will mean that the interface on the Master operates in the same manner as the BBC B B Problem Machine will only power up in the cassette filing system despite configuration settings Some keys on keyboard do not work properly Solution This is generally due to a cracked track on the keyboard PCB This is simulating a key being continually depressed To ascertain which key run the following BASIC program 10 FOR T 1 TO 127 20 IF INKEY T S THEN PRINT T 30 NEXT T The key numbers returned may be checked against the list on page D 2 39 of the Master Reference Guide part 1 Check the soldering under any suspect keyswitches Problem General problems with configuration also for Compa
16. s to keep better track of failures and better control on the flow of repairs Eventually this should lead to a significantly faster turnround and hence more satisfaction for your customers However for both of these procedures it is important that the correct paperwork is followed Therefore please ensure that before returning goods you have the correct paperwork To obtain this paperwork please contact our Goods Return Co ordinator Kay Morris on Cambridge 0223 214411 Doc 9990011 April1987 14 Acorn Engineering News MASTER 128 1770 DFS VERSIONS Version 2 20 X First release 2 24 i Loading with OSFILE amp FF returns A 1 File saves gt 64K work 2 23 CLOSEO and CLOSE and SHUT leaves files with correct length k Writing to extent works correctly k Unknown command as LIBFS works correctly 2 26 X OSGBPB speeded up i All four head step rates implemented i e CONFIGURE FDRIVE o 1 2 3 gives for 1770 6 12 20 30 mS and for 1772 6 12 2 3 mS 2 271 8 Software patch for spurious Motor on after 1770 reset 4 Following fixed If a a file was open b the disk had been changed c BREAK was pressed then the old disk catalogue would be written to the new disk 2 29 OSGBPB tube problem introduced at 2 26 fixed CONFIGURE FDRIVE 2 has software delay added to hardware delay This allows support of slow step rate drives with 1772 fitted ie CONFIGURE FDRIVE o 1 2 3 gives for 1770 6 12 50 30 mS and for 1772 6 12 3
17. supply unit is mounted on a printed circuit board with wiring to the unit from the main chassis This is different to the previous arrangement where the power supply unit was a unit which effectively had its own chassis As with previous units testing must take place to BS 415 and BS 5750 which are the relevant standards relating to safety The testing that these units receive on production is invalidated should any repair take place on them The Master Compact PSU is more open and relies on the earthing of the main chassis to provide an earth path Also the mains cabling which is connected to the psu via chassis mounted component needs to be dislodged if a replacement psu is fitted This means that should a PSU or other safety critical component be replaced the testing that has been carried out in production has been invalidated As this is an important safety issue Acorn require that any dealer or ASC performing such an operation test the resulting assembly to the prescribed safety standard Doc 9990011 April 1987 7 Acom Engineering News sell unsafe equipment If you wish to repair such units you will require suitable test equipment to undertake the checking You must receive prior written authorisation from Acorn including an agreement undertaking to test any of these items where PSU replacement or replacement of certain safety critical items has occurred Further information is available from Alastair France at Newmarket Road
18. t This device is responsible for decoding CPU address information into device enables selects for the system peripherals The CPU is also controlled by this device in that an access to a 1MHz slow peripheral will cause the CPU to pause MEMORY CONTROLLER CF 30058 1C20 M128 ET 1C48 Compact The prime function for this device is to control the memory paging structure for both RAM and ROM Due to the limited address range of the 6502 and 6512 CPU various techniques have been adopted to allow control of the additional RAM and ROM in the system The device contains two registers ROMSEL and ACCCON ROMSEL controls paging of ROMs and RAM in the region Doc 9990011 A pril 1987 4 Acorn Engineering News amp 8000 to amp BFI while ACCCON controls paging of the shadow and filing system working RAM in the regions amp 3000 to amp 7FFF and amp C000 to amp DFFF By programming these locations the memory map can be altered to allow access to far more memory than the CPU can address directly CHROMA CF 30060 1C40 M128 ET not used Compact This device generates the PAL or NTSC US only colour signal components required by domestic TVs Like the other devices described it is purely digital in its operation However as TV operates on an analogue system further discrete components are required to generate a suitable signal which may be modulated and passed to a TV for display Doc 9990011 April1987 5 Acorn Engineering News SPA
19. y be possible for you to open a spares account with Philips UK However many of the components are standard parts available through normal electronic component sources TUBE ULA SERVICE INFORMATION As you are probably aware we are stopping using the original Ferranti Tube ULA 9C ULA in production of turbo boards and have not used them for 512 co processor boards They have been replaced in this application by a new part the CMOS tube chip sometimes known as the AMI tube chip This new device can be used as a drop in replacement for the Ferranti ULA for internal Co processors but NOT for external second processors or ACWs For external second processors you should continue to use the Ferranti ULA in servicing until an emulator board becomes available allowing the AMI chip to be used in external second processors The Ferranti chip should continue to be used for service of ACWs Relevant part numbers are 2201 266 CMOS Tube Chip use in ALL internal co processors 0201 605 Ferranti ULA use in external second processors ACW Arrangements for the Bipolar Tube emulator will be made known when we have them available These should then be used in external co processors but NOT in ACWs as they will not physically fit Doc 9990011 A prill1987 13 Acom Engineering News REPAIR OF UNITS CONTAINING MODULES We have noticed in certain instances a tendency to return modules for replacement where a repair has been completed In an ET
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