sony kv32xbr55 - Left side of screen is totally green until warmed up, then OK

On Sat, 06 Jan 2007 11:53:31 -0500, G.M.Durrence Has Frothed:

What work did the estimate say was to be done?

Most likely defective caps in the horizontal scan area, or in the blanking circuits. If you use an ESR meter on all the caps, you will probably find the defective one. Considering the age of the set, you will most likely find many caps that are high in their ESR spec. You may end up changing a dozen or more caps if you go through the complete set.

Most of these thermo type problems are from caps starting to go defective.

To troubleshoot the set with a scope and meter, you will need the service manuals to be able to determine where you are going, and what you are looking for. This method would also be very time consuming.

Personaly, with a set that old, I would be out shopping for a new LCD type.

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JANA _____

Can anyone offer a clue about what might be causing this? I got an estimate of $250 to repair but I would rather put that on a new flat-panel LCD. I am an experienced electronics technician and handy with an oscilloscope but I am hoping someone might have experienced this problem and save me a lot of time.

Thanks for any help. G.M. Durrence (to reply remove -nospam from address)

On Sat, 06 Jan 2007 13:34:27 -0500, JANA Has Frothed:

Meaning they need to warm up before the problem went away? I can't remember when I've seen a weak cap work better when it was warm (not saying it doesn't happen). Lots of times I've lucked out with some freeze spray reviving caps. Guess the OP could wait until the set warmed up and the pic was ok then use a little freeze rather than removing dozens of caps and esr'n all of them.

That's how it always is with electrolytics, the ESR drops as the temperature rises. You can try it with any marginal 'lytic and an ESR meter, shoot the cap with freeze spray and the impedance will skyrocket. Heat it with a hair dryer and it will drop.

Rule of thumb is that if something works better as it heats up, look at the caps. If it works better cold, look at the semiconductors. If it's erratic, look at solder joints.

If it gradually fades back to normal from left to right, then the most likely cause is a bad capacitor near the flyback. It will probably be a high voltage one (160v-300v). When electrolytics start to fail, they get better as they warm up. Andy Cuffe

snipped-for-privacy@gmail.com

If the set will work ok when warmed up with the back off, I would let it warm up, run ok for a few minutes, and then apply cooling to all the caps to see if one or more respond with a bad picture. If not, then go after cooling the other components. Alternatively, you could apply heat to components when the set is first turned on and see if you can speed up the process toward getting a good picture. Method 1 is preferable.

H. R. (Bob) Hofmannn