"news.verizon.net" wrote in message
...
A friend of mine gave me an old 27 inch TV that no longer works. Upon
inspection of the insides, I noticed the "5A 125V GMA" fuse was blown. I
purchased a 10 pack of these fuses, and when I replaced it the fuse blew as
soon as the TV was plugged in again. I am assuming that there is a short
circuit on the board somewhere. How would I go about finding the short?
Is it possible the power cable or its connection to the circuit board is
related to this short?

Thanks in advance.


This can be as simple as a short circuit diode in the bridge rectifier, or
as complicated as any one or more of a number of parts in the SMPSU. In CRT
TVs the degauss posistor can also cause fuse blowing.

Note that the 'ground reference' rail in a SMPSU is actually a couple of
hundred volts negative and can easily supply lethal current!

One trick you can try instead of blowing more fuses and possibly making the
damage worse, is wire a 60W mains voltage bulb across the fuse holder - this
will limit the current to a value that avoids further damage and provides an
opportunity to measure voltages (or at least see where there aren't any that
should be). Note that once you have the bridge rectifier working it might be
possible to store a hefty charge on the big electrolytic capacitor - that
can give a very nasty bite!

In theory you should use an isolating transformer to power the set while
working on it, but the important thing is to *AVOID* touching anything
earthed while inadvertently touching any live part!