Service manual

Service Manual
Checking a 'dead' computer
This section covers the initial tests that you should
perform on an apparently 'dead' computer to discover
which module or upgrade is faulty. If the computer is
partially working (ie any faults occur after a successful
power-up) go straight to the section entitled Functional
testing on page 4-4.
Follow the instructions shown in the flow chart opposite.
Notes:
1 You may need to reconfigure the CMOS RAM to its
original (factory) default. Make sure that the customer
is made aware of this.
2 Before replacing any of the units as described below,
switch off and unplug both the monitor and computer.
What to do next
In most cases you can now use the test software
described in the section entitled Functional testing on
page 4-4 to check for and correct any other faults. The
two main exceptions to this are:
• when a fault within the keyboard prevents the dealer
test disc from auto-booting – in which case exchange
the keyboard
• when there is a floppy disc drive fault, and the test
software will not load from a known working dealer
test disc – in this case, exchange the disc drive.
If, after all the above tests, the computer still fails to
power-up and provide a screen display, return the entire
computer (with all original modules fitted) to an Acorn
central service facility for repair.
DANGER:
BEFORE ATTEMPTING TO OPEN THE COMPUTER,
OR EXCHANGE EITHER THE PSU OR PCB, ENSURE
THAT YOU HAVE READ AND FULLY UNDERSTOOD
ALL THE INSTRUCTIONS IN Part 3 - Disassembly and
assembly. UNDER NO CIRCUMSTANCES SHOULD
ANY ATTEMPT BE MADE TO REPAIR OR MODIFY
THE PSU. ANY ATTEMPT TO DO SO WILL
INVALIDATE THE ORIGINAL SAFETY TESTS
APPLIED AT MANUFACTURE AND MAY CREATE A
SAFETY HAZARD.
4-2 Issue 2, June 1991 Part 4 - Fault diagnosis