Service manual

Service Manual
Part 3 - 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
BS7002/EN60950 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.
NOTE:
STRINGENT ANTI-STATIC PRECAUTIONS MUST BE
TAKEN ONCE YOU HAVE REMOVED THE TOP
COVER.
Introduction
This chapter tells you how to break down a standard A540
or R260 computer into its serviceable modules, in order to
carry out basic checks and replace modules found to be
faulty.
It is recommended that you remove modules in the order
given in this chapter, to ensure, for instance, that no
cables are left connected to the particular item you wish to
remove.
The main unit houses the following:
• SCSI podule (and the Econet podule, in some cases)
• Backplane
• RAM and ARM cards
• Main PCB
• 3.5" floppy disc drive
• Hard disc drive
• PSU.
The keyboard, mouse and monitor are separate units. See
the appropriate third-party service information for the
monitor. The mouse is a service replacement only item.
This chapter makes reference (when it gives item
numbers) to the final assembly drawings (part number
0086,000/A sheets 1 and 2) which you will find at the back
of this manual.
Note on R225 model
Disassembly for the R225 is mostly the same as for the
A540/R260 models. Where there are physical differences (
ie not just different item numbers) these will be noted in
the relevant sections in this chapter.
Removing the top cover
1 Switch off and disconnect the computer from the mains
supply and disconnect all peripherals, including the
keyboard.
2 Place the main unit, with the rear panel facing you, on
a work surface with a clean, soft covering.
3 Remove the top cover:
• Remove the two screws in the sides of the top cover,
immediately behind the front moulding.
• Remove the three screws along the top of the rear
panel and remove the top cover by sliding it off from
the rear of the unit. You may need to spring the sides
apart slightly to make this easier.
Removing the SCSI podule
1 Remove the SCSI data cable (item 44) from the SCSI
PCB (item 4).
2 Remove the SCSI PCB and the blanking panel (item
15) by removing two screws and washers (items 52
and 62).
3 Disconnect the SCSI PCB from the backplane.
4 Remove the double-width blanking panel (item 13) by
removing two screws and washers (items 52 and 62).
5 Remove the SCSI podule from the T piece (item 16).
Notel : Some models may also be fitted with an Econet
podule as standard. You can remove this at the same
time as the SCSI podule.
Note2: R225 models are not fitted with a SCSI podule.
However, they are fitted with a ROM podule and an
Ethernet podule. To remove these, follow steps 2 to 5
above.
Note 3: Carefully store any PCBs, ensuring that all anti-
static precautions are taken.
Part 3 - Disassembly and assembly Issue 2, June 1991 3-1