Question about Sony KV-9PT20 9 in. Television

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Sony KV-9PT20 my vertical is slowing shrinking, any ideas? Thanks, STan

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  • Stanzman Jan 15, 2008

    Jaime, what I found was IC202 9v regulator in the vertical circuit going bad. Thanks for your input.



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Check for cold solder joints near or around the vertical section as well for leaky capacitors.

Posted on Jan 15, 2008


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After a few minutes picture shrinks to single line on screen and then powers off

Since the set works initially, there are likely poor solder connections at the vertical IC. If this is not addressed soon, the IC will fail and need to be replaced. The vertical IC is a small flat IC with about 11 pins or so that may be marked LA7837 or something similar. Try resoldering the pins first. If that fails to resolve the problem, replace teh IC. Feel free to post the marking here so I can verify you have the correct one.


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1 Answer

Sound, no picture...please help!

(Pasted from the one before -)

Since I can't see your screen, I'll guess.

If the picture shrinks away in the vertical, fast or slow, it is in the vertical control circuit.

If the whole picture shrinks in both axes simultaneously, the high voltage circuit is the culprit.
This section is responsible for producing the accelerating voltage for the beam so if it is dropping out (quite common after years of use) there will be nothing to speed the beam to the phosphor to produce light.

Turn up the intensity when the picture drops out to see if you have any trace of light.
If not, it is the latter problem.

If you can still see a horizontal line that flickers a little (from video content) then it is the first problem described.

IF the flyback (HV) transformer is still available, it will cost somewhere between $25-$100 US (many lower cost sources have disappeared) plus labor.
Depending on whether the fault was the flyback or the high power transistor that drives it, there could be additional parts needed.

Since you indicated that it operates OK for a while, it could also be something as primitive as a failed solder joint and these can be tough to find (=$$ labor).

Jun 02, 2008 | Sony KV-32XBR250 TV

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maybe the bytes of the memory are not enough for this case^_^

Feb 21, 2008 | Sony FD Trinitron WEGA KV-32FS120 32" TV

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120VAC dead

There should be a small fuse on the circuit board inside the tv. Sometimes the fuse is soldered direct to the board and not in a holder. Hope this helps you,,, Mechanic

Jan 18, 2008 | Sony KV-9PT20 9 in. Television

1 Answer


In electronics dust has nothing to do. cleaning will not solve your problem your problem is due to trouble in vertical section. mostly it is due to electrolytic capacitor in vertical section is is common problem. also check supply to vertical section. "THE SCREEN SHRINKS TOWARDS THE TOP OF THE SCREEN FOR A FEW SECONDS BEFORE THE PICTURE TURNS UPSIDEDOWN THEN TURNS BLACK." is called fold over. regards thanks

Sep 12, 2007 | Sony KV-32S42 32" TV

2 Answers

Up and away

problem in your vertical circuit look for cold solder joints.

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