8040024 Rev. A (6/94)
4
Table 2: Troubleshooting
Fault
Possible Cause
Corrective Action
Panel meter fails to
indicate a reading.
Power switch is off.
Turn switch on.
Power cord not plugged in.
Plug in power cord
Fuse blown on rear panel
of indicator.
Replace the fuse.
No power coming from power
source.
Check the service fuses, cir-
cuit breakers, and wiring
associated with power source
and repair as needed.
Defective interconnecting cable.
Check continuity and replace.
if needed.
CAUTION
When checking diode or connec-
tions to diode, do not use a multi
meter which could subject the diode
to more than five milliamperes for-
ward current, or more than 200
volts reverse bias. Excess current
or voltage will permanently damage
the diode.
Connections to the diode sensor are
loose or disconnected.
Check the continuity at the
cryopump connections pins 3
and 4. Repairs must only be
made by a qualified
technician.
Polarity of diode connection is
incorrect.
Check the polarity.
Defective front panel meter.
Check the millivolt output of
electronics. It should be 0-35
mv. Replace the meter if the
signal is present and the
meter is not reponding.
Defective electronics.
Repair as required by a
qualified technician.
