A TV which appears to be dead except for a once a second or so tweet or flub
usually indicates an overload fault in the power supply or a short in one of
its load circuits. In some cases, the low voltage (including B+) will just be
reduced to a fraction of their normal value as a result of an overload on one
of the outputs - usually the main B+.
|NotTaR of Television Sets : Dead TV with periodic tweet-tweet, flub-..
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This may be caused by a shorted rectifier in the power supply, flyback, or
even the yoke, but check the the loads first. Wait a few minutes for the
filter caps to discharge (but stay away from the CRT HV connector as it may
retain a dangerous and painful charge for a long time), use an ohmmeter across
the various diodes in the power supply. Using an ohmmeter on the rectifier
diodes, the resistance in at least one direction should be greater than 100
ohms. If it is much less (like 0 or 5 ohms), then the diode is probably bad.
Unsolder and check again - it should test infinite (greater than 1M ohms) in
Summary of possible causes:
- Bad solder connections.
- Other shorted components like capacitors.
- Other problems in the power supply or its controller.
- Bad flyback.
- Short or excessive load on secondary supplies fed from flyback.
- Short in horizontal yoke windings.
- Problem with startup drive (cycling on overvoltage).