APX 525/625 Generator Revision C Diagnostics
©
2005 Del Medical Imaging Corporation
7/5/2005 Page 168
Check for a shorted commutation capacitor
1. Turn off power to the generator and allow 5-10 minutes for the inverter capacitors
to discharge. Verify with a voltmeter that 0 VDC is measured across the inverter
capacitors as well as on the commutation capacitors. (These terminals are
located on the outside of the generator, at the rear of the power module panel).
2. Disconnect the wires and copper straps from both commutation capacitors.
3. Place an ohmmeter across each capacitor to check for a short.
Check for missing input or defect on the kV Regulator board feedback circuit
or the gate drive circuit
1. Turn off power to the generator
2. Place the kV Regulator on an extender card
3. Connect an oscilloscope to R4 and logic ground, setting the time base for 100
microseconds
4. Make an exposure and check for 2 – 3 pulses 80 microseconds in duration. If
pulses are not present, the kV Regulator board may be the problem
5. Check for presence of +25 VDC supply voltage to the switching transistors at the
anode of CR5
6. Make another exposure and check for output drive pulses at R18 and R19
7. Connect a 2-channel oscilloscope to R44 and R45 on the kV Regulator and note
the feedback during an exposure. If no feedback is present, the kV feedback
cable may be defective or may have a bad connection at the high-tension tank or
power module
Check for failure of inverter board components
1. Turn off power to the generator and allow inverter capacitors to discharge for 5-
10 minutes. Verify with a voltmeter that there is 0 VDC across the inverter
capacitors
2. Measure the resistance of each SCR out of circuit in forward and reverse bias
mode. Check gate to cathode measurements also. Replace components and/or
inverter board as necessary
3. Check for loose wiring connections in the inverter circuit. Pay close attention to
the push on connections to the SCR gates
Check for Malfunctioning mA/Rotor board
1. Turn OFF power to the generator
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