Ametek DPA1 Series Installation, Operation And Troubleshooting Instructions page 41

Phase/AMP Series DPA1/DCPA1
5-20. Check BIAS/MAN control P2 as follows:
a. Turn off power. Connect the positive (+) lead of the multimeter to terminal TB1-4, and the negative (-) lead
to terminal TB1-6.
b. Turn on power. While observing the multimeter, adjust the BIAS/MAN control on the Firing Circuit Module
through its range. The multimeter should indicate a range 8 to 24 V dc. If the multimeter indicates the
specified value, proceed to paragraph 5-22. If the multimeter does not indicate the specified value, replace
BIAS/MAN control and repeat this test.
5-21. Turn off power. Open the internal feedback loop of the DPA-1 as follows: carefully unsolder the wire
connected at feedback transformer T2-2, -3, or –4.

Opening the feedback loop permits tests of individual circuits without interaction from other
circuits. If the feedback loop is not opened, there is a high probability that all circuits will either be
turned full on, locked off, or falsely indicate other malfunctions.

With the feedback loop open, only a very small rotation of the BIAS/MAN control (in the MAN or
CW direction) is required to go from "full off" to "full on", and the response will be sluggish.
However, normal operation should be observed for each circuit unless a fault exists.
5-22. Check summing amplifier circuits as follows:
a. Turn off power. Connect the negative (-) lead of the multimeter to terminal TB1-2, and the positive (+) lead
to the positive (+) side of capacitor C4.
b. Turn on power. While observing the multimeter, adjust the BIAS/MAN control through its range. The
multimeter should indicate a smooth operating range of at least –7 V dc to +7 V dc. If the multimeter indicates
as specified, proceed to paragraph 5-23. If not as specified, replace operational amplifier integrated circuit
AMP-1 and repeat this test.
5-23. Check soft start circuit as follows:
a. Turn off power. Connect the common lead of the oscilloscope to terminal TB1-2. Connect the probe of
the oscilloscope to the positive side of capacitor C4.
b. Position BIAS/MAN control fully counter clockwise.
c. Turn on power, and obtain oscilloscope display. While observing the oscilloscope, rapidly position the
BIAS/MAN control fully clockwise. The display on the oscilloscope should start from –7 Volts or less and rise
rapidly to +7 Volts or more in approximately 200 (+20) milliseconds. If the oscilloscope display is as specified,
proceed to paragraph 5-24. If the oscilloscope display is not as specified, check the following components.
Observe previous WARNING; repeat test if any components are replaced.
(1) Capacitor C4.
(2) Resistor R7.
(3) Transistor Q7.
Document 9100030
NOTE
AMETEK HDR Power Systems
Trouble Shooting
35