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Some problems with old TV

 
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john42
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PostPosted: Mon Feb 26, 2007 7:11 pm    Post subject: Some problems with old TV Reply with quote

Hello all, I have an old TV (model "Tesla Color 110 ST"), which still works okay, but recently some problem started to appear: the TV works fine, until a there is a completely black screen (e.g. transition between ads). Then the TV emits a series of "pop" sounds (repetition rate about 5hz), which stops after a second or two and the TV works normal again. With each "pop", the screen turns blank and a bright vertical line in the upper half of the screen can be seen for a moment. The "pop" sound comes from the back of the TV as well as from the speaker. To me this sounds like high voltage sparking over (black screen=more HV, something gets overvolted?) This TV uses a high-voltage cascade multiplier, can this be at fault?
And yes, I know I could just trash this TV and buy a cheap new one, but if this is simple to fix, it would be great.

Thanks! Very Happy
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Frank
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PostPosted: Mon Feb 26, 2007 11:31 pm    Post subject: Reply with quote

Get a solder tool and start to resolder every thing in the horizontal and vertical also resolder fly, good luck,
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gilloz



Joined: 03 Feb 2007
Posts: 33
Location: So. Cal High Desert

PostPosted: Tue Feb 27, 2007 6:24 am    Post subject: old TV Reply with quote

Remove the back from the TV and with an air compressor, blow out all the dust that may have accumulated in the set. Dust bunnies can cause an occasional spark or two. Next, with the back off, turn ON your TV in the dark and look in the back and see if you can locate the source or component(s) that these sparks are emanating from. You can also inspect the main board, with power OFF, and see if any components are discolored or burnt. Do this first before you attack your set with a soldering iron.
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john42
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PostPosted: Tue Feb 27, 2007 5:56 pm    Post subject: Reply with quote

Guess I'll never more bother with this TV. I got the back off, cleaned everything around the HV circuits, got out the deflection board, reseated all "daughter" boards (the TV is "modular" coneption) also the flyback, resoldered everything around the horizontal section, replaced two wires that were completely "dissolved" (the insulation was falling out), and put it back together. When I switched it on, I was awarded with a humming sound and suspicious hissing noises coming from the back of the TV. I even didn't bother to watch it if there is still the "clicking" problem.
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john42
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PostPosted: Wed Feb 28, 2007 2:52 pm    Post subject: Reply with quote

Hmm. today I turned the tv on even with the strange noises coming out, however they stopped after awhile but the speaker was still humming.
The "clicking" problem was not solved. Maybe I'll look at it in dark if I can see sparks, if I cannot, the tv is going to trash
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john42
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PostPosted: Wed Feb 28, 2007 5:29 pm    Post subject: Reply with quote

Just letting you know that I have fixed my original problem with this TV. I remembered that I once dismantled a similar TV long time ago and kept the electronics from it, so I just replaced the horizontal drive board and no more clicking.
The sound humming problem still persists. The frequency of the hum seems to change (a tone or so) when switching channels over. I think the humming sound "creeps" from the vertical osc. (switching over channels= the vertical osc. free run freq. is slightly lower), but I have no clue how to fix this. The sound was ok previously so it is obviously a bad connection.
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