Service manual

Main unit assembly
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.
Assembly is generally the reverse of the disassembly
procedures, but take care with the routing of cables and
ensure that leads are not trapped when refitting
assemblies to the main unit. The following points are also
worth noting when you assemble the computer.
Power supply unit
When installing the PSU, the system should be tested for
satisfactory earth continuity in accordance with
BS7002/EN60950 and DC insulation.
Ensure that you refit the earth wire exactly as shown in
detail B of the final assembly drawing (part number
0092/100/A), which you will find at the back of this
manual.
Also make sure that you connect the faston power
connections to the main PCB in the correct order, which
is as follows:
PL2
-5V
purple wire
PL3
+12V
yellow wire
PL4
0V
black wire
PL5
0V
black wire
PL6
+5V
red wire
PL7
+5V
red wire
Speaker
When refitting the speaker, ensure that you replace the
rubber sealant (item 74) on each side of the speaker.
Disc drives
When refitting the backplane/drive support tray, note that
the tray has two tabs which slot into the front of the main
unit and four clips, two at each side, holding the tray in
place. Ensure that the two tabs on the tray slide fully into
the slots at the front of the unit. If they are not completely
in place, there is a risk of damage to the disc drives when
the unit is moved.
PCB
On some models of the A5000, care is needed when
assembling the main PCB to avoid damaging the EMC
gasket. As you slide the PCB board into the main unit lift
the rear panel, to ease the gasket fingers over the back
edge of the unit.
Keyboard
The computer may be fitted with either one of two
keyboards:
• Panasonic (fitted on most models)
• Keytronic (on some early models).
Both keyboards are identical on the exterior; they only
differ internally, in that they have different PCBs.
Disassembly
1 Invert the keyboard and place it on a soft, level
surface.
2 Remove the eight cross-headed screws securing the
two halves of the case and carefully lift the base
moulding away.
3 The PCB in the Keytronic keyboard is fixed to the top
moulding by six No. 6 x 0.25" screws.
The PCB in the Panasonic keyboard is fixed to the top
moulding directly by four screws, and also by means
of two metal brackets (with four screws and washers).
For the Panasonic keyboard, first remove the two
screws and washers fixing the brackets to the top
moulding, then remove the remaining screws fixing
the PCB directly to the moulding (you can leave the
brackets attached to the PCB).
For the Keytronic keyboard, remove the six screws
fixing the PCB to the top moulding.
4 Note that the reset switch cap must be removed from
the original keyboard and fitted to the replacement.
Assembly
Keyboard assembly is generally in reverse order, with
the following notes:
Slot the PCB support tray under the two fixing screws at
the end furthest from the keyboard cable, then insert the
remaining screws. Check that all keys clear the cutouts
in the top moulding before finally tightening all PCB
fixing
screws.
Mouse
The mouse is a service replacement only item.
2-4 Issue 1, November 1991 Part 2 - Disassembly and assembly