Vertical foldover problem in Sears brand TV.
 

Hello.

I have a Sears brand 27 inch television. Internally it is a JVC. The only
thing that looks like a part number on the main circuit board is
CKF1010-CU2-1.

Recently at the top of the screen I've started to see really bright lines
alternating with regular brightness lines. The bright lines still have some
picture in them but it appears to be flipped backwards. I believe this is
called vertical foldover. Am I correct on this?

Initially the problem only occured after turning the set on, they would
eventually disappear. However lately it has become really bad, starting
almost one third of the way down the screen, and never going away. Although
they do receed abit.

Does anybody know where I should look to start troubleshooting this problem?
I'm an electronics hobbyist. In the past I was able to repair a complete
vertical collapse problem on this set. It turned out to be a bad vertical
power amplifier (an LA7832). I'm thinking it might be a capacitor in the
vertical output circuit, but I'm not sure. How close should the values be
to the values on the capacitor itself.

I would appreciate whatever guidance you can offer me. Thank you.

You are right in what you think look for high esr caps,. this is the most
likely reason for the problem.


"Craig McLean" wrote in message
news:9ksyd.568912$%k.532804@pd7tw2no...
Hello.

I have a Sears brand 27 inch television. Internally it is a JVC. The
only
thing that looks like a part number on the main circuit board is
CKF1010-CU2-1.

Recently at the top of the screen I've started to see really bright lines
alternating with regular brightness lines. The bright lines still have
some
picture in them but it appears to be flipped backwards. I believe this is
called vertical foldover. Am I correct on this?

Initially the problem only occured after turning the set on, they would
eventually disappear. However lately it has become really bad, starting
almost one third of the way down the screen, and never going away.
Although
they do receed abit.

Does anybody know where I should look to start troubleshooting this
problem?
I'm an electronics hobbyist. In the past I was able to repair a complete
vertical collapse problem on this set. It turned out to be a bad vertical
power amplifier (an LA7832). I'm thinking it might be a capacitor in the
vertical output circuit, but I'm not sure. How close should the values be
to the values on the capacitor itself.

I would appreciate whatever guidance you can offer me. Thank you.

On Thu, 23 Dec 2004 05:03:01 GMT, "Craig McLean"
put finger to keyboard and composed:

I have a Sears brand 27 inch television.

Recently at the top of the screen I've started to see really bright lines
alternating with regular brightness lines. The bright lines still have some
picture in them but it appears to be flipped backwards. I believe this is
called vertical foldover. Am I correct on this?

Initially the problem only occured after turning the set on, they would
eventually disappear. However lately it has become really bad, starting
almost one third of the way down the screen, and never going away. Although
they do receed abit.

Does anybody know where I should look to start troubleshooting this problem?
I'm an electronics hobbyist. In the past I was able to repair a complete
vertical collapse problem on this set. It turned out to be a bad vertical
power amplifier (an LA7832). I'm thinking it might be a capacitor in the
vertical output circuit, but I'm not sure.

Yes, change the electrolytic caps in the vicinity of the vertical
output IC.

Here is a datasheet with application circuits:
http://www.steveselectronics.com/files/la7832.pdf


- Franc Zabkar
--
Please remove one 's' from my address when replying by email.

This is usually from defective capacitors in the vertical section. It is
best to do an ESR test on them to determine the defective ones.

--

Jerry G.
======


"Craig McLean" wrote in message
news:9ksyd.568912$%k.532804@pd7tw2no...
Hello.

I have a Sears brand 27 inch television. Internally it is a JVC. The only
thing that looks like a part number on the main circuit board is
CKF1010-CU2-1.

Recently at the top of the screen I've started to see really bright lines
alternating with regular brightness lines. The bright lines still have some
picture in them but it appears to be flipped backwards. I believe this is
called vertical foldover. Am I correct on this?

Initially the problem only occured after turning the set on, they would
eventually disappear. However lately it has become really bad, starting
almost one third of the way down the screen, and never going away. Although
they do receed abit.

Does anybody know where I should look to start troubleshooting this problem?
I'm an electronics hobbyist. In the past I was able to repair a complete
vertical collapse problem on this set. It turned out to be a bad vertical
power amplifier (an LA7832). I'm thinking it might be a capacitor in the
vertical output circuit, but I'm not sure. How close should the values be
to the values on the capacitor itself.

I would appreciate whatever guidance you can offer me. Thank you.

If this is a JVC 27 inch set look for and change C424 100mfd/35V and C425
470mfd/35V. they are near the Vertical IC.

--
-------------------------
Bob La Rocca
Lindenhurst, NY
"Craig McLean" wrote in message
news:9ksyd.568912$%k.532804@pd7tw2no...
Hello.

I have a Sears brand 27 inch television. Internally it is a JVC. The
only
thing that looks like a part number on the main circuit board is
CKF1010-CU2-1.

Recently at the top of the screen I've started to see really bright lines
alternating with regular brightness lines. The bright lines still have
some
picture in them but it appears to be flipped backwards. I believe this is
called vertical foldover. Am I correct on this?

Initially the problem only occured after turning the set on, they would
eventually disappear. However lately it has become really bad, starting
almost one third of the way down the screen, and never going away.
Although
they do receed abit.

Does anybody know where I should look to start troubleshooting this
problem?
I'm an electronics hobbyist. In the past I was able to repair a complete
vertical collapse problem on this set. It turned out to be a bad vertical
power amplifier (an LA7832). I'm thinking it might be a capacitor in the
vertical output circuit, but I'm not sure. How close should the values be
to the values on the capacitor itself.

I would appreciate whatever guidance you can offer me. Thank you.

Thank you all for your assistance. Capacitor C424 turned out to be the
culprit.

"Bob" wrote in message
...
If this is a JVC 27 inch set look for and change C424 100mfd/35V and C425
470mfd/35V. they are near the Vertical IC.

--
-------------------------
Bob La Rocca
Lindenhurst, NY
"Craig McLean" wrote in message
news:9ksyd.568912$%k.532804@pd7tw2no...
Hello.

I have a Sears brand 27 inch television. Internally it is a JVC. The
only
thing that looks like a part number on the main circuit board is
CKF1010-CU2-1.

Recently at the top of the screen I've started to see really bright lines
alternating with regular brightness lines. The bright lines still have
some
picture in them but it appears to be flipped backwards. I believe this
is
called vertical foldover. Am I correct on this?

Initially the problem only occured after turning the set on, they would
eventually disappear. However lately it has become really bad, starting
almost one third of the way down the screen, and never going away.
Although
they do receed abit.

Does anybody know where I should look to start troubleshooting this
problem?
I'm an electronics hobbyist. In the past I was able to repair a complete
vertical collapse problem on this set. It turned out to be a bad
vertical
power amplifier (an LA7832). I'm thinking it might be a capacitor in the
vertical output circuit, but I'm not sure. How close should the values
be
to the values on the capacitor itself.

I would appreciate whatever guidance you can offer me. Thank you.