Service manual

Main keyboard sub-test
For this sub-test, the display clears and the main
keyboard matrix is displayed with the following title at the
top of the screen:
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.
As you move across the keyboard pressing the keys in
the correct order, the key that is pressed should
disappear from the display. The test continues in this
way until all the keys up to the function key F12 have
been tested.
If you press the wrong key nothing will happen. If you
press two keys (the correct key and one other) the
screen is shown in inverse video and the depressed
keys are shown on the screen. If a key fails to disappear
after three attempts, the program displays a failure
message at the top of the screen and then prompts you
to press the Break key. The program then exits to the
Keyboard/ Mouse report screen. Refer to the section
entitled Action if keyboard fails on page 1-15.
If the keyboard functions correctly, the program moves
onto the next test.
Numeric keypad sub-test
For the numeric keypad sub-test, the display clears and
the cursor and numeric key matrixes are displayed on
the screen. The two key matrixes are tested separately:
first the cursor keys, then the text editing keys, and then
the Print, Scroll Lock and Break keys.
Finally the numeric matrix is tested, starting with the 0
key and working along the matrix in the same pattern as
before, finishing with the # key.
If you press the wrong key, nothing will happen. If you
press two keys, this is highlighted in inverse video. If a
key fails to disappear after three attempts, the program
displays a failure message at the top of the screen, and
then prompts you to press the Break key. The program
then exits to the Keyboard/ Mouse report screen. Refer
to the section entitled Action if keyboard falls on page 1-
15.
If the keyboard functions correctly, the program moves
onto the next test.
Keyboard LED sub-test
This test checks that the LEDs on Caps Lock, Scroll
Lock and Num Lock are working.
The screen clears and the following is displayed:
Running Keyboard LED Tests
CHECK <CAPS LOCK> LED IS ON
1 Check that the caps lock keyboard LED is the only
LED on, the other two are extinguished.
2 Press F5 to PASS or F8 to FAIL the test (do this for
each subsequent LED test). Check the caps lock is
extinguished, hence all keyboard LEDs are off.
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.
Keyboard/mouse report screen
At the end of a successful test the following screen
is displayed:
KEYBOARD & MOUSE TEST VX.XX DEALER
PASSED Logitec Mouse Test
PASSED Reset Button Test
PASSED Stuck Keys Test
PASSED Keyboard LED Test
PASSED Main keyboard Test
PASSED Numeric Keypad Test
PASSED MOUSE TEST
PASSED KEYBOARD TEST
THIS SUB_TEST HAS PASSED
PRESS <SPACE BAR> TO CONTINUE
The message that the keyboard has passed the sub-test
refers only to the non-subjective test elements and
should not be interpreted as an overall pass, since you
may wish to fail the UUT on a subjective test element.
Note: During the soak test neither the keyboard nor the
mouse tests are executed (see the section entitled
Performing soak tests on page 1-17).
Action if keyboard fails
Substitute the existing keyboard for a known working
keyboard and retest.
If the fault lies with the original keyboard, disassemble
the keyboard unit (see Part 2 - Disassembly and
assembly) and inspect the keyboard PCB for damage,
loose sockets, stuck keys etc. If you cannot find any
obvious fault, return the keyboard PCB (not the entire
keyboard) to an Acorn Authorised CSW for repair.
If the working keyboard fails, disassemble the computer
case (see Part 2 - Disassembly and assembly) and
inspect the main PCB for the correct positioning of the
following shunts:
• LK1 shunt between pins 1 and 2
• LK2 shunt between pins 1 and 2
• LK4 shunt between pins 1 and 2
• LK5 shunt between pins 2 and 3
If these are correct then remove the main system PCB
and return it to an Acorn Authorised CSW for repair.
Part 1- Fault diagnosis and repair Issue 1, November 1991 1-15