NotTaR of Television Sets : Excessive high voltage                  
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Excessive high voltage

Any significant increase in HV should cause the X-ray protection circuits to kick in and either shut down the set or modify the deflection in such a way as to render it harmless.

Symptoms include arcing/sparking of HV, smaller than normal picture, and under certain scenarios, possible excessive brightness.

Causes of the HV being too high are:

  1. Excess B+ voltage to the HOT. The likely cause is to a low voltage regulator failure.

  2. Open snubber capacitors across the HOT. These are under a lot of stress and are located near hot components so failure is possible.

  3. Incorrect excessively long scan drive to HOT caused by failure of horizontal oscillator/sync circuits. However, other things like the HOT will probably blow up first. The picture will definitely be messed up.

  4. Failure of HV regulator (tube sets and a few solid state sets - actual HV regulators are relatively uncommon today.) This may result in an underscanned (smaller than normal) picture.