"Ken Fowler" wrote in message
...

On 13-Oct-2008, "Steve Ashman" wrote:

Thanks for the advice, but I think I have made an informed decision to
cease
work on this TV as too many people have told me on the group and in real
life that I am more than likely to end up touching something that could
kill
me. The set does not have a mechanical on off switch, but the fuse blows
as
soon as the TV is plugged in, before the standby switch is pressed. As I

said, I am most likely discontinuing work on this TV. I found a similar
one
in working condition for 25 dollars on craigslist. Thanks again.

In all the responses to this posting, the one thing I believe no one has
mentioned is the need to obtain a schematic and servicing information for
the TV. Without the schematic, you are flying blind. Some of us could
make a start at trouble shooting a shorted power supply by a visual check
of the components on the various circuit boards and making resistance
checks on the obvious power rails. Sometimes wisdom comes from experience
and the wisdom helps to identify dangers. But there is usually no
substitute for a schematic if the damage is not visible.

Good luck and stay safe.

Ken Fowler, KO6NO

Although this is fundamentally true for a lot of equipment, unless you have
a detailed understanding of switchmode power supplies, the schematics will
be of little use to you. There are many techniques used nowadays, for power
saving and power factor correction, which really muddy the waters around the
front end of a switcher. Even the way that the primary side high voltage
rail is derived, may be at best not obvious, and often just downright
confusing, if a PFC IC is used, and the supply is a 'universal' type with
automatic input voltage sensing. Locating a suitable 'ground' point on the
primary side can be a very dangerous undertaking, and often, the schematics
can be misleading in this respect.

Given this particular poster's declared skill level, a schematic might have
helped to identify if there was a noise filtering cap at any appropriate
point just inboard of the power lead, but beyond that, I think that he would
probably have been on a loser with this particular repair, so posession of
service info would have been irrelevant.

But yes, in general, I would agree that if you have the skills to be working
on a particular piece of equipment, schematics are certainly desirable.

Arfa