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.
|NotTaR of Television Sets : Excessive high voltage
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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:
- Excess B+ voltage to the HOT. The likely cause is to a low voltage
- Open snubber capacitors across the HOT. These are under a lot of
stress and are located near hot components so failure is possible.
- 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
- 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.