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Vertical foldover problem in Sears brand TV.

C

Craig McLean

Jan 1, 1970
0
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.
 
M

mark

Jan 1, 1970
0
You are right in what you think look for high esr caps,. this is the most
likely reason for the problem.
 
F

Franc Zabkar

Jan 1, 1970
0
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
 
J

Jerry G.

Jan 1, 1970
0
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.
======


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.
 
B

Bob

Jan 1, 1970
0
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.
 
C

Craig McLean

Jan 1, 1970
0
Thank you all for your assistance. Capacitor C424 turned out to be the
culprit.
 
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