2. Service
Functional-Group-Diagnostic Trees (Diagnostic Section 2)
71
2.1.3.0.0 A12 Module Test
1 Power on the instrument.
2 Use a DMM to measure the A12 output voltages at the module
solder-lug connections.
3 Verify that they are within the ranges shown below:
+5V supply: at least +5.28 Vdc
+12V supply: at least +12.08 Vdc
-12V supply: at least -12.08 Vdc
QUESTION: Are all voltages approximately zero?
If Yes: Remove power, replace A12, and retest.
If No: One or two are less than specified, Go to, 2.1.3.1.0.
NOTE
A situation could occur during troubleshooting to cause similar
symptoms. If, for example, one of the output voltages were
accidentally shorted to another power supply output voltage, the
protection circuits within the A12 module will shut down all the
output voltages. In order to recover from this protection mode, the
ac power must be removed from the instrument for at least 30
seconds. Then reapply ac power and all output voltages should
return to normal. If they do not, replace A12 and retest.
2.1.3.1.0 Rule Out A1 or Module Fault
1 Remove all power from the instrument.
2 Measure the resistance (to the chassis) of each supply voltage on the A1
motherboard.
3 Verify that they conform to the following ranges:
+5V resistance: 2.0
+12V resistance: 10.0
-12V resistance: 10.0
QUESTION: Do the resistances meet or exceed the values shown
above?
If Yes: Remove power, replace A12, and retest.
If No: Go to, 2.1.3.2.0.
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