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TROUBLESHOOTING & REPAIR
F-78 F-78
COMMANDER 400
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ABNORMAL SOLENOID PULL & HOLD COIL WAVEFORMS
1V
20 ms20 ms
200 MV
5 ms
The scope pictures above are exam-
ples of a short at the output of both
the pull and the hold coil circuits on
the control PC board. The overcur-
rent circuits in the pull and hold coil
circuits will shut down the circuit when
an overcurrent is sensed, preventing
damage to the circuit. The waveform
on the left will cause the solenoid to
not pull in. The waveform on the right
will cause the solenoid to pull in, then
drop out. Check for shorted solenoid
coils and grounded leads.
SCOPE SETTINGS
Volts/Div.......................1V/Div.
Horizontal Sweep...20 ms/Div.
Coupling.............................DC
Trigger.........................Internal
SCOPE SETTINGS
Volts/Div...............200 MV/Div.
Horizontal Sweep.....5 ms/Div.
Coupling.............................DC
Trigger.........................Internal