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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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panasonic TV picture
I have a 27 inch Panasonic TV (pana-black tube) that is about 8-10
years old. The picture has always been good until lately. The top portion of the screen (about 4-5 inches) begins to display a bit brighter than the rest. The rest of the lower portion is only slightly shaded (as compared to the top), although the shading difference is hardly even noticeable. However, in the line that seperates the two shadings, displayed images get scrunched. So you see a normal forehead of a person and from the neck down everything is normal, but their entire face is scrunched down into the line. They look funny but it is annoying. If you give the front bottom of the casing a modest tap, the line goes away and the top shading is the same as the rest of the tube. However, it returns indiscriminately and its frequency is increasing. Are these the symptoms of a major repair or tube replacement? or something more minor that is worth fixing? With a TV this age, replacing the tube doesn't seem wise as the cost would be better spent on a new one. It also doesn't seem wise to take it to a shop and spend $30 to have someone tell me it isn't worth fixing. Thus I am looking for someone who may have already experienced this problem and knows the scoop on my TV. C. Frank |
#2
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Probably weak capacitors in the vertical deflection circuit.
If the tv looks good and does not have color bleed to the right even when the contrast and color are turned up all the way, and the black and white pictures actually look black and white, the tv is worth fixing. If you take it into a reputable shop, usually under a $90 total repair. David |
#3
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This is exactly what I had, since you mention tapping makes it go away
you might have a dry/cold solder joint on one of the vertical IC pins. in My set it was an LA7838 or something similar. Just hit eag of the pin with a soldering iron and you might be good to go, one additional test is to plug the set in and while running tap the heatsink that the vertical IC is bolted to with a wooden dowel, if the picture exhibits the behaviour you mentioned or it goes away you know it's a cold solder joint |
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