Mitsubishi Projection TV Loses Sync

[snielson]

I have a Mitsubishi WS-65613 TV that has developed a problem. After the TV is on for a while it will suddenly appear to lose horizontal sync. Actually I could be wrong on that. The pitcture just becomes a mess. So far we have been able to fix the problem by turning the TV off and right back on again. We don't even have to wait for anything to cool down.

That right there has me a little puzzled. It seems problems often get better as they warm up.

Once the picture goes bad it doesn't matter which input I put the TV on.

This is not the commong cap problem on the DM board that causes the blinking light issue. I fixed that a number of years ago. I replaced the 4 caps and it has been good until now.

I have looked things over and so far I don't see any obvious bulging or leaking capacitors.

As my test equipment is limited, I'm having trouble getting a heading on this problem. I'm not sure if I'm chasing the power supply issue or something on the signal board. Or, one of the other several boards.

I do have the schematics.

I have fixed several TV's in my life, but I admit I'm very much a rookie. Does anybody have some suggestions?

[Derek23]

Re: Mitsubishi Projection TV Loses Sync

I had that problem on some CRT TVs and were caused by bad caps (with leakage but looking fine even if they aren't lytics) on horizontal section on TV (those near the flyback and h transistor).
regards

[snielson]

Re: Mitsubishi Projection TV Loses Sync

I didn't look much in the deflection end of the frame. It sounds like I need to check out the horizontal down there.

I managed to get a picture of what I'm seeing. Definitly a horizontal scroll. It took a few attempts with a slower exposure to capture it.

Thanks.

[Krankshaft]

Re: Mitsubishi Projection TV Loses Sync

I'd still check for bad caps on the power supply, in the horizontal drive section (the circuitry connected to the primary of the horizontal drive transformer), and caps on the horizontal output with an ESR meter.

I have had plenty of TVs with bad caps that showed no external signs of failure.

An Orion made set comes to mind it had a bunch of low temperature 85c Rubycons with high ESR causing all kinds of problems on the set. The caps were fine but the rated temperature was too low they got replaced with 105c Panasonics.

[snielson]

Re: Mitsubishi Projection TV Loses Sync

It did turn out to be caps on the horizontal output section. I pulled checked and replaced 5 caps. The only one that really tested bad was C5A10 which is a 100uf cap right next to a large heat sink and transistor.