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Trouble Shooting
b. Check for firing pulses on gates of Q1 and Q2. If SCR's are being triggered, proceed with the general
trouble shooting procedures, paragraph 5-17.
5-15.
Output Controllable From 0% to 50% Only. This symptom indicated that one of the power SCR's is
not firing.
a. Check for proper firing pulses to both power SCR's as described in paragraphs 5-26 and 5-27. If the
proper pulses exist to both power SCR's, replace power SCR that is not firing. It can be located by shorting
gate to cathode on each power SCR. When the gate and cathode are shorted on the SCR which is firing, the
output will drop to zero. Shorting gate to cathode on the non-firing SCR will not affect output.
b. If proper firing pulses do not exist at both power SCR's, proceed with general trouble shooting procedures,
paragraph 5-17.
5-16.
Output Controllable from 50% to 97% Only. This symptom indicates that one of the power SCR's is
continuously gated.
a. Check for proper firing pulses to both SCR's as described in paragraphs 5-26 and 5-27. If firing pulses are
correct and variable to both SCR's, firing circuit is properly gating SCR's.
b. Short gate to cathode on each power SCR. Output will drop to an uncontrollable 50% when the power
SCR that is being properly gated is shorted. If gating cannot be stopped by shorting gate to cathode on the
power SCR which is gated continuously, replace it.
*Percentages of input Voltage, as measured by "average reading" meter such as Simpson 260 or similar type.
5-17.
GENERAL TROUBLE SHOOTING PROCEDURES.
5-18.
Perform steps a through f of paragraph 5-10, if not already accomplished. If the output Voltage cannot
be varied as stated in 5-10 step f, accomplish procedures in the following paragraphs, in the sequence given,
until the trouble is located and corrected. (Repeat step f of 5-10 to verify correction.)
DO NOT make or remove test equipment connections to the DPA-1, or attempt to work on it,
with input power turned on. Hazardous Voltage is present on heat sinks and at input and
output terminals when power is on.
A multimeter (Simpson 260 or equivalent) and an oscilloscope are required for the following
tests.
5-19.
Check the regulated DC power supply as follows:
a. Turn off power. Connect the positive (+) lead of the multimeter to terminal TB1-5, and the negative (-) lead
to terminal TB1-6.
b. Turn on power. The multimeter should indicate 24 (+4.8) V dc. If the multimeter indicates the specified
value, proceed to paragraph 5-20. If the multimeter does not indicate the specified value, check the following
components. Observe previous WARNING; replace faulty components and repeat this test.
(1)
Zener diodes DZ2 and DZ3.
(2)
Resistors R14 and R15.
(3)
Capacitor C5.
(4)
Rectifiers D1 through D4.
(5)
Power transformer T1.
(6)
Associated Wiring.
34
WARNING
NOTE
AMETEK HDR Power Systems
Phase/AMP Series DPA1/DCPA1
Document 9100030
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Table of Contents
Troubleshooting
