Acorn A5000 Module Level Service Manual
Copyright © Acorn Computers Limited 1991 Published by Acorn Computers Technical Publications Department Neither the whole nor any part of the information contained in, nor the product described in this manual may be adapted or reproduced in any material form except with the prior written approval of Acorn Computers Limited. The products described in this manual, and products for use with it are subject to continuous development and improvement.
Contents About this manual Part 1 - Fault diagnosis and repair Introduction Test equipment required Checking a 'dead' computer Action if PSU fails Action if main PCB fails Action if upgrades fail What to do next Checking a partly working computer 1-1 1-1 1-1 1-3 1-3 1-3 1-4 1-4 Before the tests Safety considerations Backing up the test disc Validating the test equipment Creating a test IDE hard disc Replacing the customer's hard disc Connecting the customer's equipment Saving the customer's CMOS RAM sett
A5000 Module Level Service Manual Replacing the customer's hard disc 1-19 Switching off the equipment Disconnecting the equipment Packing 1-19 1-19 1-19 Part 2 - Disassembly and assembly 2-1 Introduction Removing the top cover Removing the backplane Removing cables Removing the main PCB Removing the disc drives Removing the speaker Removing the front plastic moulding Removing the power supply unit Main unit assembly Power supply unit Speaker Disc drives PCB Keyboard 2-1 2-1 2-2 2-2 2-2 2-2 2-3 2-3
About this manual This manual is a module level service manual for the Acorn A5000 computer. It is intended as a guide for suppliers at Acorn Service Centres to enable them to trace and repair faults at a module level. Suppliers are not expected to undertake repairs at a component level, as surface mount technology is used on the printed circuit boards of the A5000 computer. Any modules which require component level repairs should be sent to an Acorn Authorised Central Service Workshop.
Part 1- Fault diagnosis and repair Test equipment required Introduction This chapter is a guide to the diagnosis and repair at a modular level of basic faults in the Archimedes 5000 series computer system. It consists of algorithms to enable you to trace and remedy faults in a 'dead' computer, followed by instructions for running the Archimedes functional test software, which is designed to isolate faults in a computer which is partly working.
1-2 Issue 1, November 1991 Part 1- Fault diagnosis and repair
Action if PSU fails There are three ways in which the power supply unit (PSU) may fail: • complete failure • individual rail failure • thermal shutdown The complete failure of the PSU is indicated by the following symptoms: • no cooling fan noise • no green LED on the front panel • no caps lock LED response when caps lock key depressed First check that the fuse in the mains plug has not blown. To do this, remove the fuse from the plug and check with a continuity tester.
What to do next Once you have repaired a fault and the computer is functioning, we recommend that you use the test software described in the following section entitled Checking a partly working computer, to check for and correct any other faults. Notes: 1 You must only connect the power after you have made all the other connections. 2 You must switch off the equipment and disconnect from the mains supply before removing any other connections.
Part 1- Fault diagnosis and repair issue 1, November 1991 1-5
Creating a test IDE hard disc To avoid overwriting the customer's hard disc during testing, prepare a test hard disc. You will need the following equipment: • IDE hard disc to be initialised (UUT) • A5000 test disc (Acorn part number 0292,824) • A5000 series test station, which is made up of an A5000 series computer with the hard disc removed and a keyboard attached (do not use a customer's computer for this test) • Standard RGB colour monitor (Analogue RGB) and cable.
Saving the customer's CMOS RAM settings You need to save the contents of the CMOS RAM before any of the tests are run, and restore them when the last test is over, otherwise the settings will be overwritten This is because the test software uses the CMOS RAM to control the test sequence and store the results. Follow the procedure given below to save the customer's CMOS RAM settings. 1 Insert the test disc (0292,824) into the floppy disc drive.
Running the functional tests About the tests The test disc (0292,824) contains various menu-driven tests. The menus are generated from a set of text files. (You can generate new text files if you wish). There are two types of test: • subjective — you must judge whether the equipment passes or fails these tests. For this reason it is a good idea for you to familiarise yourself with the correct results given by a known good computer (see the section entitled Validating the test equipment on page 1-4).
Action if the battery backed RAM test fails Memory test The screen will clear and the following menu is displayed: MEMORY TEST VX.XX DEALER Amount of Memory 2 Mbytes Running four phase memory test. Lower memory limit &000088BC Upper memory limit &00141EA0 Phase one : incrementing pattern.... Phase two : Cycling bits.............. Phase three : TRUE Hierarchy.......... Phase four : FALSE Hierarchy.......... PASSED.....
External port tests Hardware check The test continues by running a comparison check between the test data file and that which is fitted to the computer. The screen will clear and the following will be displayed: COMPUTER TYPE TEST VX.XX DEALER PASSED CPU version matches PASSED MEMC version matches PASSED OS version matches PASSED Memory size matches PASSED ST506 int. correct setup PASSED ST506 ext. correct setup PASSED IDE int.
Figure 1-3: Printer test Action if floppy disc drive fails Disc interface test The screen will clear and the following will be displayed: FLOPPY DISC TEST VX.XX DEALER Passed Write Protect Test. Passed Verification Test.
Also check that the main PCB links are set correctly. See Appendix F - Main PCB links, plugs & sockets for LK18, LK19 and LK21. Try to format a new floppy disc and retest the drive by attempting to read the original disc on another machine. Note that if this fails the disc may be corrupted. As a final measure, try substituting a known working floppy disc drive. Depending on the outcome of this test, return either the main PCB or the drive to an Authorised Acorn CSW for repair.
Action if video tests fail Standard colour test The screen test displays four colour bars red, green, blue and grey scale. Each colour bar is divided into 6 sections. The number at the top of the screen is the value sent to the individual colour gun. Only one gun is driven at a time for the red, green, and blue bars. The grey scale bar is produced by equal amounts driving each of the colour guns.
Keyboard and mouse tests Note that for the mouse test you will need a mouse jig template to perform the test (see Appendix A - Mouse test jig template). Reset button sub-test During this test you are asked to press the Reset button to test the operation of the switch. If this button works, the program moves onto the next sub-test automatically. If the test fails, refer to the section entitled Action if keyboard fails on page 1-15. Stuck key sub-test This sub-test tests for stuck keys or mouse buttons.
Main keyboard sub-test 3 This test is repeated for the remaining two keyboard LEDs, the display giving you suitable prompts. Note any LED failures before continuing with the next test. This is a subjective test. If the test fails, refer to the following section entitled Action if keyboard fails. Main Keyboard Test Press each key in turn, starting at the bottom left (Caps lock) moving across to the bottom right (Ctrl) key, then up a line to the left hand Shift key.
Test report At the end of this sequence of tests, a report screen shows the status of the tests. REPORTS VX.XX DEALER PASSED PASSED PASSED PASSED PASSED PASSED PASSED PASSED PASSED PASSED PASSED PASSED Hardware Check Memory Test Floppy Disc Test Keyboard Test CMOS RAM Test Time Test Mouse Test Parallel Port Test Serial Port Test Sound Test Video Test IDE Interface Test Select the Hard Disc Exerciser option from the list of individual tests.
When you run the hard disc formatter program, the screen clears and the following information is displayed (the figures given are typical for a 40MB hard disc): HARD DISC FORMATTER Format which drive (4-7)? 4 Drive 4 is an IDE drive IDE drive ADFS:4 identifies itself as : Description : Firmware Version : Configuration : < ? cyclinders, ? heads and ? sectors/track> This disc was last formatted using the standard shape :
Figure 1-4: Procedure after repair 1-18 Issue 1, November 1991 Part 1- Fault diagnosis and repair
Restoring the CMOS RAM settings When you have finished testing, you need to restore the customer's original CMOS RAM settings: 1 Press the Shift and Break keys simultaneously. This produces the top level menu: MENU VX.XX UN-DEF (A) Test Suite (B) Individual Tests (C) Load / Save CMOS (D) Quit Select the test type of your choice 2 Select option (C) Load / Save CMOS. This produces the following menu: LOAD / SAVE CMOS RAM VX.XX UN-DEF 1. Save CMOS RAM to disc. 2. Load CMOS RAM from disc. 3. Exit Program.
Part 2 - Disassembly and assembly DANGER: BEFORE REMOVING THE TOP COVER, ENSURE THAT THE COMPUTER SYSTEM HAS BEEN SWITCHED OFF AND THE MAINS PLUG REMOVED FROM THE SUPPLY. REMOVING THE TOP COVER GIVES ACCESS TO THE POWER SUPPLY. ALTHOUGH THE POWER SUPPLY IS DESIGNED TO COMPLY WITH BS5850 CLASS 1, YOU MUST STILL TAKE CARE TO ENSURE THAT NO METAL OBJECTS FALL (OR ARE PUT) INTO THE POWER SUPPLY UNIT THROUGH THE VENTILATION HOLES.
Removing the backplane Note that the backplane is only fitted on models with a hard disc drive. The backplane (item 9) sits inside the main unit, attached to the main PCB and the backplane/drive tray (item 25). 1 Remove the four fixing screws from the backplane. 2 Remove the backplane from the main board connector SK9 by pulling the backplane upwards. 3 Unscrew the two fixing screws on the lower blanking panel and remove this panel, together with the gasket shield (item 26).
5 The tray has two tabs which fit into the front slots of the unit and four clips, two at each side, holding the tray in place. Remove the tray from the main unit by grasping both ends of the support metalwork. The whole assembly should lift and the end tags disengage from the sides. See the diagram below. Removing the front plastic moulding 1 There are six spring plastic clips on the front moulding ( item 28), three each on the top and bottom, attaching it to the main unit.
Main unit assembly PCB On some models of the A5000, care is needed when DANGER: WHEN REFITTING OR FITTING A REPLACEMENT ASSEMBLY, CHECKS SHOULD BE MADE FOR EARTH CONTINUITY AND FOR DC INSULATION. FOR DETAILS REFER TO Appendix C - Earth continuity testing AND Appendix D - DC insulation testing - class 1. NOTE THAT THE PSU IS A SERVICE REPLACEMENT ONLY ITEM.
A5000 Module Level Service Manual Appendix A - Mouse test jig template 1 Using wood or metal strips, construct a test jig with the dimensions shown in the template (plan view) above. 2 Secure the test jig to a firm, flat, horizontal, non-slip surface. 3 Mark out the three button boxes shown on the template. Notes: • The INSIDE dimensions of the jig are important. • The sides of the jig should be LESS than 5mm high. • The Middle and Right button boxes overlap.
Appendix B - Serial port loopback plug* Item Part no.
Appendix C - Earth continuity testing Test procedure Equipment required An earth continuity tester or appliance tester capable of sourcing 8-25A derived from an AC source with a no-load voltage not exceeding 12V, for example, CLARE A433R-IO. IIt is recommended that the calibration and operation of the instrument is checked frequently enough to ensure its accuracy. DANGER: THE FOLLOWING TESTS INVOLVE HIGH CURRENTS BUT LOW VOLTAGES.
Appendix D - DC insulation testing - class 1 UK information only Before testing Equipment required Check the mains lead and plug for any physical damage and replace if necessary. A portable appliance tester or an insulation tester that provides 500V DC ONLY. Note that the computer contains RFI capacitors on the PSU input. It is recommended that the calibration and operation of the instrument is checked frequently enough to ensure its accuracy. DANGER: THE FOLLOWING TEST INVOLVES HIGH VOLTAGES.
Appendix E - Monitor adaptor cables This appendix describes how to make adaptor cables for monitors not supplied with a 15-way VGA connector. Adaptor type 1 Adaptor type 3 The cable supplied with some TV-type monitors is terminated at the computer end with a 9 pin D-type plug. You need a 15-way plug to 9-way socket adaptor: The cable supplied with some Multiscan monitors is terminated at the computer end with a 9-way D-type plug.
Cable type 5 You need to make this cable to use with monochrome monitors which have a phono input socket. You need a 15-way plug to phono socket adaptor with resistors, to mix the separate red, green and blue signals into a composite monochrome signal (you can fit these components into a 15-way connector shell). You need to make an adaptor cable that has a 15-way Dtype plug on one end, and a phono plug on the other.
Appendix F - Main PCB links, plugs & sockets Introduction Link Fitted This appendix describes the links, plugs and sockets on the main PCB of the A5000 computer. LK8 Yes LK9 Effect Yes P1 P2 Shunt 1-2 Sig.
Link Fitted LK19 Yes Effect Default P1 PL8 P3 No Floppy disc power connector. P2 P3 P4 nc PL9 IDE hard disc drive data connector. This is a Yes 40 way box-header containing all the signals required by the drive in AT mode. Shunt 1-2 Used to connect pin 34 of floppy drive connector B (PL11) to the DISC CHANGE I/P of 82C710 P1 P2 P3 LK22 Yes Yes DISC CHANGE VP on 82C710 Pin 34 of drive connector nc None Connection for Power and Hard disc activity LEDs.
Sockets Skt Fitted Function/Specification SK1 Yes RGB video socket. This is a 15-way mini D-type socket providing an interface to RGB monitors and Scan TVs. RGB video levels are 0.7V Pk-Pk into 75 Ohm. Sync voltage levels are >= 2.0V (TTL). Pin Signal 1 2 3 4 5 6,7,8 9 10 11 RED GREEN BLUE ID[2] OV +5V (750mA fuse) OV IT) ID 1 /SCARY func. switching H NC 12 13 1 14 15 SK2 Yes VSYNC/CSYNC ID[3] Stereo headphone output. This is a 3-way 3.
Appendix G - Final assembly parts list Introduction The parts list in this appendix details the components used in the final assembly of the Acorn A5000 computer. These components, together with their corresponding part numbers, are illustrated in the final assembly drawing given at the end of this manual. Final assembly (Hard and floppy disc versions) Note: Items in bold are only in the hard disc machine.
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