Isolating Hardware Faults
Isolating H ardware Faults
Use the following procedures to help locate a hardware malfunction.
You c an isolate the symptoms to the amplifier or probe by substituting a known
good probe or amplifier. If you suspect that you have a defective probe and you
don’t have another compatible probe, you can use the calibration adapter in place
of the probe
to verify some of the amplifier functions.
Information about some of the failures that can occur with the amplifiers and
probes is l
isted. (See Table 36.) (See Table 37.)
Table 36: Amplifier hardware faults
Symptom Possible cause Repair action
Amplifier does not power on.
LEDs do not turn on and fan
does not work.
Internal power supply problem
Connector loose between main board
and front panel
Front panel is defective
Check for +15 V on power supply connector J2, pin 1
at main board. If OK, replace amplifier board. If not,
replace power supply.
Secure ribbon cable from front-panel assembly to
main board
Replace front-panel assembly
LEDs do not turn on and fan
works.
Internal power supply problem
Connector loose between main board
and front panel
Front panel is defective
Check for +15 V on power supply connector J2, pin 1
at main board. If OK, check power supply test points
on main board: +5VD, +5VA , -5VA, +10V, -10V. If
these voltages check OK, replace the front-panel
assembly. If not, replace the main board.
Secure ribbon cable from front-panel assembly to
main board
Replace front-panel assembly
LEDs turn on and fan does not
work.
Defective fan or defective power
supply
Check for greater than +7V at fan connector J3, pin
1 at main board. If present, replace fan. If not, check
for +15 V input from power supply. If +15 V is present,
replace the ampli fier board. If not, replace the power
supply.
LEDs turn on in a random
pattern (different than is
documented in this manual)
Front panel is defective Replace front-panel assembly
One amplifier range does
not work, other range is OK.
(TCPA300 only)
Defective amplifier circuit
Replace main board assembly
Table 37: Probe hardware faults
Symptom Possible Cause Repair Action
Probe Open LED stays
continuously lit, even with
the probe slider closed.
Open coil in probe. Substitute probe with another probe or the Calibration
Adapter - if the Probe Open LED goes out , coil is open
- repair bad connection or replace coil
80 TCPA300/400 Amplifiers and TCP300/400 Series Current Probes Service Manual
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