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Sony TV - Picture Problem

Hello,

I have a Sony Trinitron KV27S22 (December 1997). A couple of days ago, it developed a picture problem. Rather than try to describe it, I have placed the following photos on the web:

Image of color bars: Behaving OK -

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Image of color bars: Exhibiting problem -
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The problem will set in anything from a few seconds to a few minutes after cold-starting the set. The problem will persist for a few seconds before the display completely disappears. Only a cold reset will restore the image. Audio is fine.

I have done some troubleshooting and have narrowed the problem to what I think is a capacitance issue. Using a painter's stick (wooden!), I tapped the various components on the main board and found that the tapping could induce the problem. However, if I hold the ground of the audio connectors, the tapping does not create the problem. When the problem is present, grabbing the ground of the audio connector clears the problem.

The most sensitive part of the board is shown at:

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I have a copy of the Sony service manual for this set but, before I merrily begin replacing all the capacitors, I would like to know if anyone knows a specific cause and/or that I am barking up the right tree.

Many thanks in advance,

John Miller.

Reply to
John F Miller
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How does tapping on the board narrow it down to a capacitance issue?

Any mechanical vibration testing that changes the symptom points to a connection problem. It is possible, though highly unlikely, that the leads to a capacitor have become partially disconnected internally.

I would start by a good visual going over with a light and magnifying glass the solder connections on the bottom of the board.

Reply to
dkuhajda

Thanks for your quick reply.

I suspect a capacitance issue based on the problem not occurring (or even reversing) when I touch a ground on the board (e.g., the audio input ground). When tapping, there's no specific component that is most sensitive and, if, instead of tapping, I apply a more constant force to the components, I cannot reproduce the problem. I have disconnected and reconnected all the connectors to the main board with no effect. I have looked at the underside of the board with a magnifying lamp but couldn't detect any obvious problems.

John.

Reply to
John F Miller

Sonys from this period had a solder problem esp around the tuner and tuner board. I repaired a few recently with this problem. Sam talks about it here:

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Very careful inspection is a must. Some of the solder might have to be sucked off and replaced. The bad joints have a frosted look with a grainy look and sometimes veins running through them. I usually reheat everything and resolder everything that looks bad. Quite tedious. Just did an eMac with the same problem. richard

Reply to
spudnuty

Thanks! I will check that area very carefully.

John.

Reply to
John F Miller

I like those do it yourself guys. They mess up then they bring it in to us and it ends up costing more to have it fixed now then as it would if they would of came in before messing with it.

Reply to
tvguy

Resolder your vertical output IC561.

This will solve your problem.

Resolder the Horizontal Driver Transformer while your in there for good preventive maintenance

-- ========================== Jeff Stielau Shoreline Electronics Repair

344 East Main Street Clinton,CT 06413 860-399-1861 860-664-3535 (fax) snipped-for-privacy@snet.net ========================
Reply to
Shoreline Electronics

Based on his description (problem shows for a while then screen disappears) the protection circuitry is kicking in to blank the picture. A loose connection (or bad solder joint) can definitely cause this. If not a solder joint problem, it is doubtful that a component failure problem would allow him to get a normal picture to submit.

I have a Sony KP-41T15 that has a similar "line paring" problem but in my case there are faulty components in the vertical circuit as the problem condition is continuous from when the set is turned on. The vertical voltage feed to the jungle IC is twice what it should be (approx 3V versus

1.5V). I am suspecting the jungle IC as well but first I have to find the problem components(s).

Bruce

Reply to
Bruce H

Correction to post:

Reply to
Bruce H

Have you done what Jeff suggests ?

Reply to
kip

Jungle IC301 CXA1477 is your line pairing culprit.

Best place to buy these are from B & D

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Original Sony IC's in Original Sony packaging. Around $50.00

Yeah...you can scrounge them up for $20 or so here and there.....but once ya ya bit by a bad one or one that lasts a couple days....OEM is the only way to go on these.

-- ========================== Jeff Stielau Shoreline Electronics Repair

344 East Main Street Clinton,CT 06413 860-399-1861 860-664-3535 (fax) snipped-for-privacy@snet.net ========================
Reply to
Shoreline Electronics

Thanks for the link, Jeff! I'll get around to this and report back (some time after I replace the plumbing in my house and install the insulation on the exterior walls).

So far all the supply voltages seem to be approximately where they need to be but I may have a leaky transistor. Don't want to bug anyone until I do some proper investigation...

Bruce

Reply to
Bruce H

Thanks, Jeff!

I followed your suggestions yesterday and, after being on continuously for more than 20 hours, the problem seems to have gone away.

Regards,

John.

-- John F. Miller

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high performance tools for music and video

Reply to
John F Miller

Just a follow up to my television problem (Sony KP-41T15). I bought the Jungle IC from B & D and it solved the problem. Interesting that the plastic in this set is very fragile and cracks easily. I used slivers of ABS pipe and ABS/PVC solvent to repair cracks.

My next task is to set the convergence (particularly the red CRT gun as I had to replace it). Swapped the yolk and positioned it as close to the original as possible. Everything works except the picture is a little out.

Just wanted to say thanks for the information.

Bruce

Bruce H wrote:

Reply to
Bruce Haugh

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