Know anything about tv repair?

[rwest]

A friend of mine at work says he has an older Mitsibishi 27'' console floor model he just replaced. He said it has a great picture but the only sound he gets from it is a high pitched sqeal. He said he give it to me if I wanted it. I'd love to have it, if the sound is reasonably repairable.

I figure a shop'll probably cost at least $150 bucks for service let alone any parts needed. For that it can go the dumpster. I've never done tv repair but this sounds to me like it may be an easy fix. So I'm punting into the wind.

High pitch squeal coming from old floor model tv? Repairable for novice?

[juppy]

Repairable by a novice? I doubt it. Most of the tv's I've seen that have been built in say the last 10 to 15 years or so, pretty much have everything integrated on one board. You'd end up having to replace that whole board ($$$) or having to figure out the exact part that's bad and replacing that (not easy). Plus, if you don't know what you're doing, you can get a rather hard shock from the picture tube/flyback transformer.

[backithink]

Tv repair isnt as hard as it seems as long as you are comfortable enough with your skills especially soldering, i have a 48 inch jvc that had a convergence problem paid over $400 to have it repaired and not only did they not fix it they made it worse, so i got online found a repair manual for $20 found out the problem ordered the parts and replaced the sdk board. but one thing you want to think about always is do i trust my self, even if a tv is unplugged it can still electrocute you even in new hd tv's it takes a couple of hours for this voltage to disapate. It all depend on how comfortable you are with it, lol atleast it isnt your main tv if you fry it, i thought i killed mine pluged it in and it didnt turn on, lol cat stepped on the switch to the surge protector.

[Lespaul20]

Can you just disconnect the speaker and use an external system for sound?

[rwest]

Hey, thanx for the replys. Well I've done some soldering and am comfortable enough around electical components, I've just never opened up a tv.

I did a little digging and it seams a high pitch or sqeal is fairly common, but mostly from what I've read is on a working unit. It seems the sqeal is most likely a transformer as juppy suggests. Of course then it may have an additional problem of no sound. Whereas I can test and replace a speaker if neccessary. But if the speaker is good I don't know where to go from there.

The main board would be the easist route to go, but then I'd probably be throwing too much into it. Anybody have any clue how much a transformer like this might cost? Or maybe about how much a few parts may cost using replace and test.

Juppy when you mentioned trying to find out which part on the board may be bad, is exactly what directed me to to post in the first place. So I'm kinda looking for some help in this direction. I know how to check for voltages with a multimeter and have been inside PCs, fax machines and copiers. What I don't know is board level diagnosis. I was kinda hoping for the "Yep, I seen it. repace this and that" fix.

I was shocked at some of the things I've read online concerning how to diagnose and and repair these noises. One said hold a pencil on the board and listen to the other end. (done similiar on a car ) And the repairs seemed outrageous. Super glue on the transformer's coils, or hot glueing the whole thing. Sounds like a bandaid, rather than a repair.

Last question, how long could a transformer possibly hold a charge?

[flanzig1]

A transformer does not hold a charge, capacitors do and so does the picture tube in CRT type TVs. A squeal or high pitch sound or hum through the speaker could also be a cold/broken solder joint someplace in the audio path. I have had this problem in stereos and have found the bad connection by using a nonconductive tool(plastic stick) to press on areas that I think are for audio. If the sound changes, getting close to the problem area.

[juppy]

Yeah, the main things you have to watch out for, as far as getting shocked, are capacitors and the picture tube. The flyback transformer shouldn't shock you unless you try working on it while it's powered up. Without having a schematic that shows the voltages of all the areas of the board, it can be pretty hard to trace a problem down to the individual component. The stuff flanzig1 posted about checking joints with a nonconductive stick will work sometimes if it's just a cracked solder joint (and that would be a relatively easy and cheap fix). There are numerous things that can let noise into the audio portion of a circuit.....bad capacitor that isn't doing it's job of filtering the noise out, leaking capacitor, cracked solder joints, etc etc. If you do decide to try and fix it though, just be sure to NOT touch the small back end of the tube and especially do not stick a screwdriver or any kind of tool under that thing that looks like a suction cup with a wire coming out of it on the middle of the tube. That's the wire coming from the flyback transformer and it connects directly to the inside of the tube. If a tube's not discharged, it *can* hold a charge of 10,000 to 30,000 volts. Granted, the old way of discharging the tube was to hook a grounding cable to the tv's chassis ground and then alligator clip the other end to a flat blade screwdriver and then hold on to only the plastic handle of the screwdriver while you put the screwdriver tip under that cup till you hit the connector.....at which point there will be a loud snap if the tube's still charged. I don't personally like trying to do that though, so I'm just usually careful about what I touch and stay away from the "shocky parts".

[backithink]

well if your careful you can take the cover off turn it on and see if you can identify the region of the problem heck even an old stethoscope from a thrift store or a garage sale could help you hear better, just be extremely careful when doing this. lol even a kids plastic one may be better cause you dont have to go sticking a metal thing into a live tv just in case you know the dog decides to nudge you while you are looking er listening



Guess i should have read better lol your problem may be with the tube being on its way out, when they age they make a great deal of sound thats something you just have to learn to live with untill it decides it doesnt want to work anymore

[rwest]

That's alot of help guys. I'll be sure to stay away from the shocky parts. 10,000 to 30,000 volts huh? That'll staighten your hair! I'll have to be very careful , maybe I'll get lucky and it'll just be a few cold solder joints, or bad caps. Ya know if I go inside and appears to be too intense, I won't touch it.

Juppy thanks for the laymans description. Flanzig thanks for the clarification on some components. I knew the capacitors held charges but I thought these charges dissipated over time. Unit 's been off over two weeks now. Don't know much about transformers.

Backithink thanks for the final note on the tube. The guys says the picture's as good as new.

I talked to him today, he said it may be a bit before I can get it. It's still holding up his new 44'' plasma. LOL Oh well, even if I have to wait, it's still a free toy.

[juppy]

Originally Posted by rwest I knew the capacitors held charges but I thought these charges dissipated over time. Unit 's been off over two weeks now.

Capacitors and picture tubes *do* lose their charge over time, but it can take quite awhile for that to happen. In the electronics courses I took in college, we were told some picture tubes can hold a charge for several years. So, in other words, just because a tv has been "sitting in your grandma's closet for 4 years", don't automatically think it's discharged, because that's the exact time it'll prove your assumption wrong. Oh, and you're welcome on the "layman's terms" stuff above. Good luck with it.

[tigstah]

i had an uncle who used to repair tv's. when i was a kid, i wanted to do it to. he told me a story of one of his friends, who had electrocuted himself, and he had gone to school for tv repair. he accidentally did touched something and his found him unconscious. that pretty much was that. one of the few things i will not hesitate to call in a profession for.

[rwest]

Originally Posted by juppy don't automatically think it's discharged

Gotcha.