Sony KV-35S26 - Picture collapses

[Juan]

I have a Sony KV-35S26 that I acquired with a bad power supply and
shorted HOT. It was deader than a doornail.

Using information acquired from these posts, I replaced two switching
transistors in the power supply (2SC4834), the HOT, and the blown
fusible resistor (0.1 ohm R607) on the power supply.

Voila! The television works great--except . . .

After the set is on for a while, all of sudden the right side of the
picture starts to contract and cave in. Then the horizontal deflection
gives way to a picture that contracts into the middle and goes black.
At this point I've always quickly turned off the set, assuming that if
something's not oscillating I'm probably on the verge of shorting out
the parts that I just replaced.

I let the set sit--sometimes for 30 seconds, sometimes for a couple of
minutes--and when I turn it on again I once more have a very nice
picture. Then after another few minutes of running, the same thing
happens again. It starts to get fuzzy and contract along the right
side, and then it collapses.

I should also mention that when I replaced the HOT, I also went through
the HOT circuit and meticulously resoldered every connection (there
were a few that looked like they might have had ring cracks at the
solder joint). I also resoldered the flyback transformer.

The intermittent nature of the problem after the set's been on a while
makes me wonder if it's heat related. In addition to the components
mentioned above, are there other common failure points in the
horizontal output circuitry?

I sincerely appreciate any help you might be able to offer.

Best wishes,
Juan

 

[Leonard Caillouet]

Most likely you either missed a connection in the h-drive circuit or you
have a badelectrolytic in that circuit. There is a small value
electrolytic, .47uF IIRC, that is reported to be a high failure part in the
sony h-drive circuits. I have not found many bad ones. The culprit is
usually bad solder joints. Check the pin circuit as well.

Leonard

 

[Dani]

Replace VDR 601, it's black, there may be two depending on the model,
they are by the
two 2sc4834 regulators. They go bad sometimes. Be sure to resolder the
horizontal drive, & check the electrolytic capacitor, if it has one,
Dani.

 

[Leonard Caillouet]

Why would you replace the VDR in this case? The VDRs almost never go bad
when the cause of the failure is the output stage shorting.

Leonard

 

[kip]

And if the Black VDR was no good it would take out the 6.8ohm as well...not
to mention the 4834,s.

You have missed a bad cap or still missed adry joint.

kip

 

[Juan]

Thanks for the help and suggestions. I'll recheck the soldering and
look for a bad cap.

Juan

 

[claude]

kv35s26 hot

hi and hoping will have a anwser,
i have a kv35s26 that was already been fixed for blown 4834s but would like to know original horizontal transistor number.was replaced by 2sc5150 but not sure if its original number?
thanks regards
Claude