NotTaR of Television Sets : Horizontal deflection shutting down     
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Horizontal deflection shutting down

Confirm that the horizontal deflection is shutting down (along with the high voltage since it is derived from horizontal deflection: listen for the high pitched deflection whine, test for static on the screen, see if the CRT filaments are lit, turn up the brightness and/or screen control to see if you can get a raster) and then why:

  1. Power is failing to the horizontal output transistor - this could be due to a low voltage power supply problem, bad connection, etc.

  2. Base drive to the horizontal output transistor is failing - could be a fault in the horizontal oscillator or bad connection.

  3. Problem with the flyback transformer or its secondary loads (flyback may provide other power voltages).

  4. X-ray protection is activating - either due to excess HV or due to a fault in the X-ray protection circuitry.

If the problem comes and goes erratically it sounds like a bad connection, especially if whacking has an effect. If it comes and goes periodically, then a component could be heating up and failing, then cooling, etc.