Power Supply Troubleshooting - HP 5340A Operating And Service Manual

Model 5340A
Maintenance and Service

5-39. Power Supply Troubleshooting

Determine which power supplies are regulating at a n incorrect voltage by measuring the
a.
output voltage.
b. If any supply is a t or near zero volts, the supply could be current limiting. Disconnect the
output leads for that supply
c. Again measure the voltage. If the output is still bad, the failure exists in the power
supply circuit. Use the typical voltage charts shown to isolate the defective components.
d. If the output obtained in step 3 is now good, there could be a short circuit in the instru-
ment, or the supply could be current-limiting improperly. Substitute a resistive load for
the supply under test as listed on the next page.
If the output is still good, a n excessive load exists somewhere in the instrument. Connect
e.
an ohmmeter between ground and on the feeder line in question (which is still discon-
nected from its power supply). Start removing the plug-in PC boards until a significant
change is observed on the ohmmeter. Then isolate the execessive load. Check also for
shorted wires.
f. If the output obtained in step
sary current. Use the typical voltage charts to isolate to the defective component.
especially for the same voltage on any two leads of a transistor, indicating a shorted
transistor.
5-20
at the A30 power supply motherboard.
4 is bad, the power supply is not able to provide the neces-
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