On Nov 24, 10:11 am, "Arfa Daily" wrote:
"Tov" wrote in message

...

On Nov 23, 10:03 pm, "Jerry G." wrote:
The power supply may be in a failed condition, or there is a short
somewhere in the set. This would require proper troubleshooting, and
not guess work.

Take the set in for a proper estimate. It can be a challange for even
a skilled service tech to repair these types of faults.

Given the age of the TV (at least 17 years) I can't really justify the
expense. I'm prepared to spend my own time, though, in the hope that
it will be a fairly inexpensive fix, once identified.

It would first be necessary to determine if the power supply was
'self-faulting', or tripping as a result of detecting an over-current
condition on one of its rails. Without experience in the field, this may
prove difficult for you to determine, as sometimes, trip conditions can be a
little bit 'round and round in ever decreasing circles'.

Generally, self-faulting of the power supply is caused by faulty
electrolytic caps - which may be open circuit, short circuit or poor ESR -
short circuit secondary diodes, and occasionally more subtle problems in the
feedback circuitry. Reasons for overload tripping include short circuit HOP
transistor, faulty flyback transformer, faulty HV tuning caps, faulty E-W
modulator circuitry, faulty field output chip, faulty sound output chip, bad
joints in HOP stage and so on. To get any more specific help, you would need
to declare the make and model number, and then someone on here might be able
to point you at particular problems for that TV.

Well, I replaced the field output chip and the voltage regulator and
repaired two circuit board damaged connections in the vicinity of the
latter and it works! Just goes to show you can be lucky even though
you don't really know what you're doing. Thanks, Arfa.