High Voltage/Power Supply Issues: No Picture, HV Problems

Many times a Barco set will display no picture due to loss of the high voltage. This can be due to:

• Shorted/imploded CRT
• Bad HV splitter
• Bad HV quadrupler
• Bad EHT board
• Bad SMPS

Check to see if the set is in HV shutdown mode by looking at the red LED on the EHT board. If this LED is on, then most likely the HV splitter, quadrupler or the EHT board itself is bad. There’s no way to accurately check these components with a meter, you need to substitute parts or check your components by installing them in a working set.

Much more rare are shorted tubes. A tube that has lost its vacuum acts like a dead short to the HV section. You can completely disconnect a tube from the set by disconnecting the tube’s red HV lead from the HV splitter and then also by pulling the CRT socket from the back of the tube. Beware, there are high voltages here! Once you disconnect the shorted tube from the set, the remaining two tubes should work normally.

If the red EHT light is not on, the scan fail light is not on, but you still don’t have a picture, it’s still possible to have no high voltage. It’s possible that the EHT board has gone bad (check the fuse on the EHT board, that could be one possibility) or dead, or the SMPS may not be sending power to the EHT board.

It’s also possible that the H shift board has gone bad. There’s a pulse that comes from that board, and if it’s missing, there will be no image displayed.

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