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Sony Projection TV intermittent image problem -- KP46WT510

All:

I've been impressed in the past with the accurate answers provided here in this newsgroup (e.g., APC UPS fix), so I hope there's help again! :-)

My 5 year old Sony projection TV (KP46WT510) has developed an image problem. Here's some pictures:

Bad:

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Also bad:

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Just starting:

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Sound is OK, and I've isolated the problem to the TV (not the cable box, etc.).

The "whack" and overnight unplug "reset" tests didn't fix the problem.

There's no new EM sources nearby, other than an occasional black helicopter at night (green in the day). :-)

The signal is being delivered via standard CATV coax. The image intermittently switches between OK and the thin horizontal color bars (R+G+B) in varying proportions (never to 100% of the time). The bars vary with the input-signal.

Oddly, DVDs play fine (also through the CATV coax connection). Must be the higher resolution scan than for CATV.

So my _guess_ is the low-res circuiting that creates the CATV pictures.

I've read on-line about typical convergence problems (and replacing the two STK392-560 ICs), but my TV's image problem does not seem to be one of the common convergence image problems.

Anyone seen/fixed this specific problem? If so, how? (A service call is not likely since I'm a unrepentant diehard DIY'er)

Thanks!

Brian

(If e-mailing please be sure to edit my address)

Reply to
Brian
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No, but it is definitely not a convergence problem.

Leonard

Reply to
Leonard Caillouet

Thanks, that's a start!

Others seen or solved this problem?

-Brian

Reply to
Brian

What about checking for a glycol coolant leak from one of the CRT's onto one of the boards? If your pictures were more blotchier, Id say its time for a coolant change.

Reply to
Circuit

Glycol coolant? I though you were kidding at first. But it is there, apparently.

I pull the back cover off (after unplugging and letting it cool off for a couple of hours).

No signs of leakage, and the little rubber coolant expansion bulbs on each lamp are full.

Wiggled all the electrical connectors I could find, but no change.

"Id say its time for a coolant change." -- might be getting time for a TV change, unfortunately. Too bad ... I expected this $$$ Sony to last

15+ years like my previous Sony CRT TVs.

-Brian

Reply to
Brian

Heres the service manual in PDF:

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You might want to try some freeze spray on the flat pack IC's on the signal board. Something tells me though its probably some SMD electrolytic caps that are dried out somewhere.

Reply to
Circuit

Thanks! There's no troubleshooting table in it, unfortunately, other than for blinking lights.

Interesting. Here's a pic of a suspicious capacitor (with gray plastic blob next to the large capacitor in the center of the pic):

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The grey blob looks factory-applied to me, and is hard. What does a leaking capacitor look like usually?

Thanks, Brian

Reply to
Brian

Just pulled out the big/wide circuit board platform (held in with only three screws!) a bit, and don't see any capacitors that are bulged or have black/brown staining under them.

-Brian

Reply to
Brian

Thats RTV placed in there at the factoty. The caps I am thinking of are silver low profile SMD electrolytics. I dont really know if your TV has them, perhaps not since its a PJTV.

Reply to
Circuit

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