Ametek DPA1 Series Installation, Operation And Troubleshooting Instructions page 42

Trouble Shooting
5-24. Check the soft start reset circuit as follows:
a. Turn off power. Connect the common lead of the oscilloscope to the positive side of Capacitor C4.
b. Set the BIAS/MAN control fully clockwise.
c. Turn off power and obtain oscilloscope display. While observing oscilloscope, rapidly turn the input power
to the unit off and then on. The display on the oscilloscope should drop to 0 V dc within 5 milliseconds and
then rise to 2 V dc or more in approximately 200 (+20) milliseconds when power is applied. If the oscilloscope
display is as specified, proceed to paragraph 5-25. If the oscilloscope display is not as specified, check the
following components. Repeat this test if any components are replaced.
(1)
(2)
(3)
(4)
5-25. Check the firing circuit as follows:
a. Turn off power. Position BIAS/MAN control to mid-range. Connect the common lead of the oscilloscope to
the anode of zener diode DZ1. Connect the probe of the oscilloscope to the collector of transistor Q6.
b. Turn on power. The oscilloscope should display a pulse train as shown in Figure 4-6, waveform 2.
c. The pulse rate of the sawtooth waveform is a function of the setting of the BIAS/MAN control. Rotating the
control counter clockwise should increase the number of pulses.
decrease the number of pulses. Return the BIAS/MAN control to "0" (center).
d. If the pulse is present and adjustable as specified, proceed to paragraph 5-26. If the pulse train is not
present or the pulse rate of the sawtooth waveform cannot be controlled with the BIAS/MAN control as
specified, check the following components. Repeat this test if faulty components are located and replaced.
(1)
(2)
(3)
(4)
(5)
(6)
(7)
5-26. Check shaper circuit for power SCR Q2 as follows:
a. Turn off power. Connect the common lead of the oscilloscope to the side of C11 that is common with point
#3 on the P.C. board. Connect the probe of the oscilloscope to the junction of C9 and R22.
b. Turn on power. The oscilloscope should display a pulse train as shown in Figure 4-6, waveform 8. The
extension or contraction of these pulses is controllable by the BIAS/MAN control. If the oscilloscope displays
the specified pulse train, proceed to paragraph 5-27. If the oscilloscope dos not display the specified pulse
train, check the following components. Repeat this test if faulty components are located and replaced.
(1)
(2)
(3)
(4)
(5)
36
Transistor Q7.
Resistor R23 through R27.
Diode D12.
Capacitor C15.
Transistor Q6.
Unijunction transistor Q3.
Zener diodes DZ1 and DZ4.
Diode D9.
Resistors R9 and R11 through R13.
Rectifiers D5 through D8.
Transformer T3.
Oscilloscope must be ungrounded for this test.
Silicon controlled rectifier Q5.
Pulse transformer T3.
Resistor R21 and R22.
Capacitors C11 and C17.
Power transformer T1.
AMETEK HDR Power Systems
Rotating the control clockwise should
WARNING
Phase/AMP Series DPA1/DCPA1
Document 9100030