charging diode, and reverse-current diode.
Look for loose or broken
connections, charred resistors, and loose or broken tubes. Check the tubes
by substituting known good ones.
Before replacing a component, make sure
that the power is off.
d. Elimination of the trouble.
Your job is to repair troubles.
So
take pride in your work by doing a neat repair job. Learn how to use your
tools properly and efficiently.
e. Test circuit.
After repairing the trouble, make sure the circuit
works by performing an operational check.
f. So you see, the standard troubleshooting procedure is both logical
and systematic.
It takes you where you want to go in the shortest time.
Now, let's deal just with the modulator and see what can go wrong with it.
3.
Trouble symptom.
No modulator output pulse.
Assume you've localized the trouble to the modulator.
The first
step in troubleshooting the modulator is to check the output pulse. You can
do this easily by connecting a synchroscope to the test jack provided for
this purpose. If there is no modulator output pulse, isolate the trouble by
making the following checks:
(1) Check the input trigger pulse to the THYRATRON. If the trigger
is not present, the THYRATRON won't fire. Then, you will have to check the
timer unit.
If the trigger is present, measure its amplitude.
If the
amplitude is too low, the trigger will not fire the THYRATRON.
(2) Check the modulator plate voltage. Usually, there is a meter on
the modulator panel for this purpose. If the meter indicates no modulator
plate voltage, then check the output of the high-voltage power supply.
(3) Look for lighted filaments in the THYRATRON and charging diode.
Replace the tubes with known good ones.
(4) Check each of the components in the modulator. An open charging
choke, PFN, or pulse transformer primary will cause loss of modulator
output.
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