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LCD TV power-up problem


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#1 TDT

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Posted 16 August 2014 - 20:24

Hello everyone. I have a problem with an old Samsung LCD TV (LE32M86), maybe there are some good technicians here that can figure out what's wrong. Please note that I don't know much about electrical stuff and components, I'm just "translating" what a friend of mine says.

 

So, the problem started about a month ago when I noticed that it takes longer to power up than usual. It was like 2-3 minutes from the moment I pressed the power button on the remote till the TV was actually on. I didn't think much about it back then, but a few days ago the "delay" was about 20 minutes! The power led blinks, like it should, the backlight goes on, but the screen stays black, then the backlight switches off, and so on, till it actually manages to start. There is no problem with colors, sound, etc., so I thought it's some power issue. So I sent the tv to a friend of mine that works with electrical stuff, tv's, etc. He tested the power source and found nothing wrong with it, but he did notice that from the moment he tried to start the tv, his testing device showed 12V, then 2V, then 12 and so on, so he said there must be some component that drains a lot of power and the tv cannot start. He changed some capacitors here and there that were a little damaged, but that didn't fix the issue. Another thing he noticed is that a component heats up like crazy, in fact the only thing that heats up much more than it should. I looked it up and it's a Sigmatel SGTV5810C, the audio IC judging from what I found online. Could this be the problem?!

 

One more thing. After the tv starts, if I shut it down and start it up again, it starts normally, like it should. Only if I leave it off for more than 30 minutes it starts so slow.

 

Please, don't start with "buy a new tv" or stuff like this, if you can help in any way, then thank you, if not then please don't reply. 

 

Thanks! :)




#2 Bigkaye

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Posted 16 August 2014 - 20:42

...you should buy another one of those TVs and see if it works the same way, then return it. 

 

If something isn't getting power, but heat is being created, thats probably where the power is going. IR temp gun may help. Get the data sheet for the chip and figure out where the powers are going and see if they are getting there.



#3 a66fm

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Posted 16 August 2014 - 20:46

I should ask your friend to check the capacitors of the power supply unit

#4 OP TDT

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Posted 16 August 2014 - 20:48

If something isn't getting power, but heat is being created, thats probably where the power is going. IR temp gun may help.

Then how come the tv starts after all? Shouldn't it stay off, or in this power cycle for ever?  :/


I should ask your friend to check the capacitors of the power supply unit

That's the first thing he did. The PSU looks fine, no capacitors need replacing...



#5 Bigkaye

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Posted 16 August 2014 - 21:04

Then how come the tv starts after all? Shouldn't it stay off, or in this power cycle for ever?  :/

Why did it work fine when you got it, then only took 5 minutes and now takes over 20 to turn on?? Why does it only happen on the first power up and none after that unless 30 minutes or more has passed?? Tolerances and charging circuits coupled with a latent failure where component hasn't completely failed. Least based on what you've said. You claim one IC that gets hot fast after applying power. Heat is a byproduct of wasted power.

 

Get that chips datasheet and read it over, there should be pretty simple checks to do to tell if its functioning or not. Some may be done in circuit, like power levels while others may need to be done external to the board, checking for shorted pins. Hell, it could require an external oscillator that went out of wack and is just getting the wrong timing pulses and is faulting, creating the heat.



#6 jerzdawg

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Posted 19 August 2014 - 14:03

A few years back Samsung had a big problem with capacitors.  My flagship A650 (at the time) wouldnt turn on (just heard a few clicks).  The warranty was well over a year past but Samsung must have recognized the issue and agreed to a 1 time fix.  They sent out a tech and he replaced the whole power board (he said the caps that were originally used were very cheap).

 

http://www.cnet.com/...lty-capacitors/



#7 OP TDT

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Posted 19 August 2014 - 19:13

A few years back Samsung had a big problem with capacitors.  My flagship A650 (at the time) wouldnt turn on (just heard a few clicks).  The warranty was well over a year past but Samsung must have recognized the issue and agreed to a 1 time fix.  They sent out a tech and he replaced the whole power board (he said the caps that were originally used were very cheap).

 

http://www.cnet.com/...lty-capacitors/

Yeah, I've read about this, but my model is not on that list. No luck so far, changed a few capacitors, but the problem still exists. 



#8 Brian M.

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Posted 19 August 2014 - 19:18

Sounds like a bad inverter to me.

#9 OP TDT

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Posted 19 August 2014 - 20:16

Sounds like a bad inverter to me.

Oh, you will have to be more specific, I'm a noob at this :p Someone else told me that he had the exact same issue, with the same model, but he never got to fix it since the owner wanted it back. But before that, he noticed some fluctuating tension on the sub-board, so the issue could be there. I told my friend this, but it seems there's a lot to investigate...