Precision II Operation and Maintenance Manual C
5-6
996-0255 rev. b
Chapter V Troubleshooting
A. Electronics rack troubleshooting
This procedure is designed to allow the user to troubleshoot down to the
module level (CU, PU, CB). It does not allow for troubleshooting down
to the individual component level (IC, transistor, etc.) within a rack
module.
Equipment needed:
Volt Ohm Meter (VOM)
Oscilloscope
Standard scope probe
Phillips screwdriver
10 kΩ
1
/4 watt resistor
NOTE:
In order to perform the following test you must be able
to observe LED’s (light emitting diodes) located on the
power unit logic board. To open the power unit:
a. With rack main breaker off disconnect all cables at
rear of PU.
b. Remove the power unit from the rack and take off
its lid. The logic board is located in the front left
corner of the PU drawer body.
c. Put the unit back into rack with lid off and protrud-
ing ~8 inches from rack so that the logic LED’s can
be observed.
d. Reconnect all cables at rear of power unit and turn
on main breaker.
1) Reset system logic - turn off and then turn back on the
button switch on front of CU601C.
2) Confirm that green LED VOLT OK ENABLE is on. Look
at center of PU logic board. If it is not lit:
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