Service manual

Service Manual
Part 4 - Fault diagnosis
This chapter is a guide to the diagnosis and repair of
basic faults in the Archimedes 500 series and R200
series computer systems.
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 working.
Part 5 - Main PCB fault diagnosis is designed to help
repair centres to diagnose and repair faults at component
level on the main PCB.
Note 1: It is a good idea to familiarise yourself with the
tests by performing them on a known working computer.
Note 2: Throughout this chapter the acronym UUT is
used to mean Unit Under Test.
Test equipment required
• 100 MHz Oscilloscope
• DC Voltmeter
• test discs:
• dealer test disc (Acorn part number 0286,832)
• hard disc initialiser test disc (0286,822)
• test SCSI hard disc (see the section entitled Creating
a test SCSI hard disc on page 4-5)
• serial port loopback plug – see Appendix C - Serial
port loopback plug
• headphones (32 ohm impedance)
• analogue multisync colour monitor (suitable for super
VGA)
• hi-resolution monochrome monitor
• Epson FX80 compatible printer (Olivetti JP101 or
Epson FX80)
• 3 x blank BOOK ADFS E format write-enabled, 3.5 inch
floppy discs:
• data disc– for storing customer CMOS RAM
configuration data
• CMOS RAM test data disc– for storing the
manufacturer's default CMOS RAM settings (see
the section entitled Creating a CMOS test data file
on page 4-6)
• scratch disc– used in the disc interface test
• working keyboard (0086,900/A)
• working backplane (0186,001)
• working SCSI card (0173,010 Issue 2+)
• mouse test jig template (see Appendix A - Mouse test
jig template)
• chip extraction tool (68/84 pin)
• standard hand tools, such as screwdrivers and pliers
• earth testers (see Appendix D - Earth continuity
testing)
• isolation tester (see Appendix E - DC Insulation testing
- class 1).
Additional test equipment required
when testing expansion cards
You will need the following additional equipment when
testing expansion cards:
ROM expansion card test:
• ROM Podule Guide (0476,220)
• EPROM (0276,230-01)
• EPROM FS (0276,221) required if not fitted.
10 expansion card + MIDI expansion card test:
• a known working MIDI expansion card (0176,280)
• 10 port tester assembly (0233,020) from which only
the following parts are needed:
• port tester main PCB
• 34way IDC skt to 34way IDC skt cable assembly
• 20way IDC skt to 20way IDC skt cable assembly
• 15way IDC D type plug to 15way IDC D type plug
assembly
• Acorn Econet cable – 2 off.
MIDI expansion card test:
• a second, known good, MIDI expansion card
• 2 Acorn Econet cables (which have been labelled IN
and 0/P)
Ethernet I and II expansion card tests:
• Ethernet I and II test feedback leads – see Appendix
B - Ethernet test feedback leads (you will need to
make these)
• Ethernet T-piece
• Ethernet terminators – 2 off.
Anti-static precautions must be used at all levels of
servicing, ie antistatic matting and wrist-straps. Refer
to Part 3 - Disassembly and assembly for information
on how to gain access to the components mentioned.
DANGER:
WHEN REFITTING OR FITTING A REPLACEMENT
ASSEMBLY, CHECKS SHOULD BE MADE FOR EARTH
CONTINUITY BETWEEN THE EARTH PIN OF THE MAINS
PLUG AND THE FOLLOWING:
• THE BASE METALWORK
• THE REAR PANELS (INCLUDING BLANKING PANELS
AND CONNECTING PLATE)
• THE TOP COVER
USE AN EARTH CONTINUITY TESTER SET TO 25 AMPS.
REFER TO Appendix D - Earth continuity testing.
Part 4 - Fault diagnosis Issue 2, June 1991 4-1