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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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Old Sony KV2781R typical problems
I just picked up, from a moving neighbor who left it behind, an old 27"
Sony KV2781R, mfd March 1987. I can't pass up a freebie. When you push the on-off switch there is a click and a degaussing sound, but nothing more. Are there any frequent/common problems that I should look for first. I don't want to rebuild the whole set, but hate to just add this to the collecting garage in our landfills until I give it a go. I have a scope, but no schematic for this particular set. Been doing tv repairs since vacuum tube days, for those of you who remember what they are. :-) Advice appreciated. H. R.(Bob) Hofmann |
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It is very common that the drive IC in the power supply fails. It runs
fairly hot, and after a while the mounting screw can loosen up, and thus the IC becomes overheated. I have put small whisper fans in these sets to help cool down the power supply. If any of the decoupler caps in the drive circuits start to go high in their ESR, this IC can also be damaged. It is also best to go through the power supply, vertical and horizontal scan amplifiers, protection circuits, and check for any high ESR capacitors. The caps tend to give problems, especially in the older sets. On the odd occasion, I have had bad flybacks and horizontal output transistors fail, and also cause damage to the power supply. Considering the age of the set, and that it has not been used for a long time, I would expect the CRT to also be very weak. -- Jerry G. ===== wrote in message oups.com... I just picked up, from a moving neighbor who left it behind, an old 27" Sony KV2781R, mfd March 1987. I can't pass up a freebie. When you push the on-off switch there is a click and a degaussing sound, but nothing more. Are there any frequent/common problems that I should look for first. I don't want to rebuild the whole set, but hate to just add this to the collecting garage in our landfills until I give it a go. I have a scope, but no schematic for this particular set. Been doing tv repairs since vacuum tube days, for those of you who remember what they are. :-) Advice appreciated. H. R.(Bob) Hofmann |
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This model was long before the STRS6301 was ever invented. You most
likely have a bad flyback transformer plus shorted horiz output. |
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RonKZ650 wrote:
This model was long before the STRS6301 was ever invented. You most likely have a bad flyback transformer plus shorted horiz output. Oops - you are right! Sorry, I misread the model number sheepish look. |
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Thanks to everyone who posted. I have never in my life paid to have a
tv fixed, starting with when I was in college studying electrical engineering in 1953-1957. Put myself thru college fixing tv sets. P I have an original RCA 630ts in my basement that still gets a picture, that's 55 years old. Bob Hofmann |
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