Basic HTML Version
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phase shift networks in the gate circuits of drive SCRs
produce the new phases.
REMEDIES FOR IITOUGH DOG" LAMP PROBLEMS
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Lamp circuit failures tend to follow a pattern. Usually both
phase A and phase B lamps are lit simultaneously, or
neither lights.
Locate the malfunctioning lamp's SCR number
(displayed
Q#)
by running the Single Lamp Test. The displayed num-
ber corresponds to the SCR number screened on the Con-
trol Board. Also displayed are corresponding jack and pin
numbers.
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SYMPTOM: LAMPS ALWAYS ON
A circuit's phase A and phase B lamps may remain simul-
taneously lit. If both light with equal brilliance, you have a
shorted SCA. However one lamp may be brighter. This is a
very different problem. If both lamps are common to the
same SCR, don't replace the SCA. Instead, replace the
brighter lamp's diode, which is shorted. Now retest the cir-
cuit.
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SYMPTOM: LAMP ALWAYS OFF
If a single lamp is out, the lamp, itself may be burned out.
Or the lamp's series diode may be open. Insert a known-
good bulb. Enter the Lamp Test. Now you'll need a jumper
wire for an easy, component-level checkup ...
• CHECK THE DIODE. If you suspect an open diode,
momentarily short across the suspected part.
Lamp
lights now:
Replace the diode .
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• CHECK THE GROUND CONNECTION.
If you
suspect an open connection, momentarily jump from
ground to the SCR anode.
Lamp lights:
Proceed to the
next bullet (step).
Lamp doesn't light:
Check for an
open connection or wire... Keep the ground end of the
jumper connected. Walk the other end of the jumper
back toward the lamp. Tap the ungrounded end of the
jumper at each connection point between the anode
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