FTB 324x High Voltage Troubleshooting

In this second video installment of the FTB 324x troubleshooting series, Bill shows us how to identify failures in the high voltage circuit using three isolation steps.



FTB 324x High Voltage Troubleshooting


In this video installment, we’ll take a closer look at the high voltage circuit and walk through 3 different isolation steps to identify where a failure could lie in these critical circuits.


Tools required for testing:

  • High voltage insulated needle-nose pliers
  • Digital voltmeter rated 1000V+
  • #2 Phillips insulated screwdriver


In the first 3 steps, we identified that the high voltage warning lamp was illuminated. The lamp itself is not a complete indication if high voltage is present. It’s primarily an indicator lamp for technician safety.


Always trust what your meter tells you.


The lamp illuminates around 50 volts DC. There needs to be a 500+ VDC on the red wire TB2 and a 500- VDC on the blue wire TB2, however, so that the xenon flashhead can operate correctly.


  • Check TB2 pin 1 to ground. Reading should be 480-580+ VDC. Ensure you see the positive indication.
  • Now look at TB2 pin 3 to ground and verify 480-580- VDC. It’s critical to see a difference in polarity.


Perform Safety Checklist


1. Turn off unit via interlock switch.
2. Turn off breaker then lock-out/tag-out.
3. Allow high voltage (HV) to discharge (approximately 1 minute).
4. Test TB2 Pin 1 to ground. Voltage should read below 1 VDC to proceed.
5. Test TB2 Pin 3 to ground. Voltage should read below 1 VDC to proceed.
6. Manually short capacitors with HV needle-nose pliers to ensure that HV is not present.


First Isolation Step – Remove the Tower Load


Determine if the cable run or something inside the flashhead could be affecting the production of high voltage from the power converter. We’ll do this by isolating the tower load.


  • Remove the red and blue wires from TB2.
  • Power the unit back on.
  • See if there are any improvements in the voltage readings.


If the voltage has returned to normal ranges, there’s an issue on the tower.


  • Verify the cable runs and check for damages or splices.
  • Check the inside connections of the flashhead.


Second Isolation Step – Remove the Capacitors


If removing the tower load didn’t help, the next step is to isolate the capacitors from the high voltage circuit.


  • Using high voltage insulated pliers, remove the 5 wires leading from behind the chassis just above the HV warning lamp.
  • Re-test with your digital voltmeter.


If the voltage has returned at this stage to normal readings, there’s an issue with 1 or more capacitors.


There are 5 things to consider when trying to diagnose failures within the capacitor bank:

  • +/- 10% of the original stated value of caps in microfarads
  • Shorted/open capacitors (resistance across terminals)
  • Leaking capacitors
  • Swollen capacitors
  • Dented capacitors


If any of the caps fall into the above-mentioned categories, replace them immediately.


How to formally test a capacitor:

  • Isolate the capacitor by removing the jumper wires.
  • Place your meter into the microfarads settings.
  • Read across the top and bottom of the capacitor and verify your readings.


The stated values should be within 10% of the testing value. If reading low, please replace the cap.


Third Isolation Step – Check the Transformer


If high voltage still hasn’t returned, verify the voltage supply from the T1 power transformer.


  • Loosen the 2 screws that secure the red light module above the transformer.
  • Slide the red light module off to the side, making sure it doesn’t touch the back of the door switch or the white 3-position interlock switch.
  • Remove the white/red, white/green and white/orange wires from pins 5, 6 and 7.
  • Power the unit on and place your meter into AC.
  • Read across pins 5 and 6. You should see around 480-580 volts AC.
  • You should see around the same voltages when you test across pins 6 and 7.


If AC voltage is within these ranges, the T1 is operating correctly and you should replace the high voltage rectifier board.


If the voltage is not within these ranges, the T1 transformer itself will need to be replaced.


That completes a close-up look at the PC 324 high voltage path. Continue troubleshooting your FTB 324x xenon tower lighting system with the trigger circuit video.

Watch more xenon tower lighting troubleshooting videos:

FTB 324x Introductory Troubleshooting
FTB 324x Trigger Circuit Troubleshooting

in Xenon Lights