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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Sony KV-2730, problems with bright picture
Hello all,
My recently acquired Sony KV-2730 EC (a 28" Trinitron set, about 15 years old?) came to me with a broken chopper transistor in the power supply. I replaced that, and now the set has problems with bright pictures. I'm told the problem has existed for quite a while. When using the scart input (AV) or channel 0 (which comes through the tuner), and viewing a bright pic, the top 5 cm of the screen starts to flicker, that is, it jumps around a bit sideways. When this happens, a clicking sound can be heard from somewhere around the chopper. When the pic darkens again, the flicker goes away. Turning contrast and brightness up makes the problem worse. Note that channels 1 and up don't seem to have this problem, only the scart input and channel 0! Possibly related: Once, while I was testing the scart input, the program I was watching had a brief all white picture. The PSU shrieked and shut down. I had to cycle the power to get it working again. I watch tv through my VCR, and have one of the TV's channels tuned to the VCR's modulator. When I change channels, the set emits a short chirp that sounds a bit like the ticking sound. And if I turn the VCR off before the TV, I get the same shriek and the PSU shuts down. Any ideas? A shorted chopper is something I can easily fix, but this is a bit out of my league. And it's a nice television otherwise. BR, Ilkka |
#2
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Ilkka Huikari wrote:
Any ideas? A shorted chopper is something I can easily fix, but this is a bit out of my league. And it's a nice television otherwise. Weak electrolytics in the power supply. --- Met vriendelijke groet, Maarten Bakker. |
#3
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Sounds like the AKB can no longer adjust to the lack of beam current from
the cathodes within the CRT. When a very bright area of the raster is required the cathodes no longer can supply enough electron flow to properly illuminate the phosphors, then the AKB attempts to equalize the current through the three cathodes and causes the flicker. wrote in message l... Ilkka Huikari wrote: Any ideas? A shorted chopper is something I can easily fix, but this is a bit out of my league. And it's a nice television otherwise. Weak electrolytics in the power supply. --- Met vriendelijke groet, Maarten Bakker. |
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