I'm working on an lcd tv. There was one visibly bulging capacitor on the power supply board. I replaced it and the tv powered on but there is a high pitched screech coming from the replaced capacitor. I replaced it with another cap, and then another cap with exactly the same result. Any idea what the issue might be?
Screaming brand new capacitor.
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You have more bad capacitors in there, and they are causing the power supply itself to make the "screaming" noise.
I highly suggest replacing them all, AND using a higher voltage rating for the replacements.
I highly suggest replacing them all, AND using a higher voltage rating for the replacements.
The screaming isn't likely coming from the cap, probably it is coming from the transformer in the switching pwr supply. Primestar31's advice to use a higher rated voltage cap is good advice, keep the capacitance the same but use a higher voltage rated cap.
The cap that you replaced, did you use the same capacitance value? You usually can't just throw in any cap and there is polarized and non-polarized caps too. If it is a polarized cap, make sure that you put it in correctly, they only go in one way. They'll physically fit either way but polarized caps have a negative and positive leg that you have to pay attention to and put it in correctly. Usually the board has a mark on it for negative, you can look at other caps on the ckt board if you not sure how it goes.
Non-polarized caps can go in either way.
What brand and model TV is it? I'd be willing to bet that Primestar31 is correct and you have more bad caps in the pwr supply. Replace them and the screaming noise will most likely go away.
The cap that you replaced, did you use the same capacitance value? You usually can't just throw in any cap and there is polarized and non-polarized caps too. If it is a polarized cap, make sure that you put it in correctly, they only go in one way. They'll physically fit either way but polarized caps have a negative and positive leg that you have to pay attention to and put it in correctly. Usually the board has a mark on it for negative, you can look at other caps on the ckt board if you not sure how it goes.
Non-polarized caps can go in either way.
What brand and model TV is it? I'd be willing to bet that Primestar31 is correct and you have more bad caps in the pwr supply. Replace them and the screaming noise will most likely go away.
The other possibility is that the bad capacitor caused a transformer or coil in the power supply to overheat. This would cause flow in the tar they use to hold the coils steady. That causes the wire in the coil to vibrate and make the sound you mention. Solution is to replace the transformer. I have experienced this as well.
I suspect that something else failed in the power supply and overloaded the capacitor. Replacing the capacitor has put you back to having the original problem. Do you have a schematic and test equipment?
I've been using a straw held to my ear to isolate where the sound is coming from. I replaced that cap again with a different brand and all the other caps of the same size while I was at it. The sound moved to a smaller cap. I replaced that cap and the sound moved to the transformer which means I'm done. A new power supply is $60. Looks like I need to go that way.
LG 37LC2D. I bought it broken for $25. If I can fix it I'll likely give it to a family member. I have a similar tv already. The aggravating part is that the tv is working great other than the noise.
Amazon.com has a repair kit for the pwr supply of that set for $18.95 and $1 shipping, 12 caps are in the kit. Here's the link...
http://www.amazon.com/dp/B00AV2N8F6/?tag=satell01-20
http://www.amazon.com/dp/B00AV2N8F6/?tag=satell01-20
