Riddled TV Repair Forum

Jerry · Guest

Hello,

Quick update: The set was exhibiting the following behavior:
when you turned it off and then on, quickly, the vertical sweep would
die. And the -18V fuse feeding the STKs would instantly pop. I obtained
a quantity of the 3.15A GMA fuses, and sat down to troubleshoot. Hooked
up my 4-trace scope to a few strategic locations - the horiz sweep input
to the convergence board, a sweep signal a bit further up the line, and
the
vertical output from one of the charge pump drivers. Normal signal except
at the charge pump driver output - nothing there. Long story short, it
was
missing its -15V. The 7915 -15V regulator was misbehaving - if you
cycled power its output would come up +1V ( not only not enough voltage,
but the wrong polarity! ). So I replaced the 7915.

Now the TV works normally - for about an hour. Then R604 opens up. This
is the .1 ohm fuse resistor in series with Q603, one of the primary
power supply switching transistors.

Now that I think of it, all or most of my problems with this TV have
been in the -18V or -15V area. And I'm not alone - I understand that D605 -
a double-schottky rectifier - which feeds the -18V - is a common failure.

Anybody have any thoughts on this? Been there done that?

Google

jon · Guest

No Jerry, but I apprecaiate the feedback. What a headache. I'm
still trying to fix a KV32FS120 That won't even click at the Relay. Just 8
Blinks. Replaced the M board thinking thats where it was, but no. I'll
keep digging may be I'll come across a fix.

John