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d.
If any of the remaining signals are not within tolerance, turn the power OFF for 90
seconds, then ON again. If the fault recurs, replace the power supply.
Caution
,
Set the Power switch to OFF and the Battery Enable switch to DISABLE
before removing or inserting a plug-in card.
6.
If the voltage checks in step 5 do not detect an out-of-tolerance voltage, remove all of the
plug-in cards in the card cage. Repeat the voltage checks using the following voltage ranges
(these ranges are slightly wider than those listed in Table 3-1 because there is no load on the
power supply):
Voltage Point
+12V
-12V
+5.1V
+5.1VM
PON+
Voltage Range
11V - 14V
-llV - -14V
4.75V - 5.5V
4.75V - 5.5V
2.4V - 5.2V
a.
If the voltages are within tolerance, one of the plug-in cards is defective. Install the
cards one-by-one while making voltage checks to detect the defective card.
b.
If any voltage is out of tolerance, this could mean a faulty power supply or backplane.
First, replace the power supply. If the problem persists, replace the backplane.
A990 Self-Test Programs
The A990 self-test consists of two test programs (Test 1 and Test 2) that automatically execute
each time you turn on the computer. You also can initiate these tests by pressing Reset Switch
SW1 on the A990 CPU card. Test 1 (microcoded self-test) tests the processor at the circuit level.
Test 2 (VCP pretest) tests the processor at the functional level. For example, Test 1 tests the
hardware associated with the LIA instruction to ensure that the hardware works correctly. Test 2
executes the LIA instruction and checks the results to ensure that the instruction works correctly.
Successful completion of the tests is followed by execution of either a bootstrap loader, the Virtual
Control Panel (VCP) program, or a program sustained in memory by optional battery backup.
(Refer to the A990 Computer Reference Manual, part number 02959-90001, for information on
bootstrap loaders and the VCP.) Which of these occurs depends on how the BOOT SELECT
switches are configured. Refer to A990 CPU Card Switches in Chapter 2.
Test 1
Test 1 is stored as a microprogram in the firmware EPROM on the A990 CPU card. It executes
immediately on power-up and checks all of the hardware on the card. On successful completion
of Test 1, Test 2 is started. If Test 1 detects a failure, it stops executing and the LEDs on the CPU
card display an error code.
3-4
Service
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