Sunday, 24 April 2011

LG 32LX2R Faulty power supply.

A LG 32" LCD TV that would not power on, the fault occurred following a mains power outage.

The PSU board looked fine, no bulging or stained capacitors. Aquick google went straight to the point, somebody with identical experiences who recommended changing the output stage capacitors (circled) anyway.

http://forums.moneysavingexpert.com/showthread.php?p=27092505

post number #31



The capacitors were sourced, 14 in all. The board was of reasonable quality, no problems removing the old ones.

Here is a close up, all the old capacitors looking ok


So in went the caps. I measured all the old capacitors and they were all in spec for capacity on a basic Fluke multimeter....

However the TV now worked. I would be interested to know the failure mechanism of the capacitors but a good result and Google delivered as the capacitors really dint look suspicious.

Update:

Here is the capacitor list:

2200uf 10v x 1
1000uf 35v x 4
1000uf 25v x 2
1000uf 10v x 3
680uf   25v  x 2
100uf   50v  x 2

Update:

The likely failure for the capacitors is poor ESR, (equivelant series resistance) at given frequencies. I have access to a proper LCR bridge. A quick measure shows ESR varies with physical size on new capacitors, I will need to look into specs for given values and see if there is a large deviation from spec.

Update:

Ok, I had kept the capacitors and measured them all. Here is a table of typical ESR values. This is from a manual of an ESR meter made by Peak electronics. I hope they dont mind me using it, here is a link to there meter http://www.peakelec.co.uk/acatalog/jz_esr60.html

There are three 10v 1000uf capacitors in the TV PSU, two measured just under 0.2ohms but one measured 2.1 ohms, so it looks like this was the likely culprit.

The esr meter above can be used in circuit, I hope to try one out soon !

16 comments:

  1. Do you have a list of the condensators used in the power supply?

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  2. I do have a list, not with me now so I will add it to the blog entry later.

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  3. Hi, do you know what component B105 is on this board? I have managed to snap it off when replacing the caps. Thanks, Tom

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  4. I don't have access to the board any more Im afraid. I found what looks like a pretty good parts list. Could it be Q105 ?

    Q105 0TR387500AA 2SC3875S(ALY) NPN 5V 60V 50V

    Parts list here

    http://www.brelect.fr/ve/32LX2R.pdf

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    Replies
    1. Hi, can you share a full schematic diagramm. I need to check my PSU YP2632T. I have a schematic w/o this PSU.

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  5. Hi there, i had the same problem on my tv, i have changed all the capacitors and now i have a green light for power at the front and then the blue light at the bottom lights up then goes straight off again... hear it clicking on and off... not sure what else to check? any ideas?? cheers

    ben

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    Replies
    1. Make sure that you haven't fitted one of the caps the wrong way round. The white shadings on the top of the board denote the caps negative pole.

      Alan

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  6. Hi Ben, it could be a second fault and need some proper fault finding.......but if the TV was fine before and it just went dead, and changing the capacitors has bought it back to the point you say, from my experience of repairing things I would say go back over every bit of the TV you worked on and check nothing got damaged, a plug missed out or something got disturbed near where you soldered the new capacitors. It could all be fine but well worth a check.

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  7. i have a different problem the lcd no pwer from the remote, but it turn off well fron the remote.
    i have to turn in on in the front switch.
    thank to everybody and sorry for mi englis i write fron spain

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  8. Got similar issue, power outage and then TV is only thing not working. Stripped down & all capacitors working, someone also suggested a fuse, but not sure which as the plug was changed & tested with another unit (PC) without issue, leading me to believe the TV power unit is where fault lays....

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  9. hi
    my lg was working very well
    but today when I connect it simply does not connect
    red light keeps burning power
    but does not work with the buttons on the TV
    with the command also not
    can tell what can be please
    thank you

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  10. Good evening ... I apologize for my writing I have the same power supply board repair kit capacitors but I should also replace a damaged transformer YP2632L-T102

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  11. Solve my one, TV does not Work the Power supply 6V is OK and 24V Turns On and within few minutes it turns off.what should i do

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  12. Hello,
    Don´t know where the fuse for PSU is placed. Can´t see it on the plcture. Is it solved or does it have a socket?

    ReplyDelete
    Replies
    1. The fuse is soldered on. It's down by the power socket. F101

      Delete
  13. I had the same or similar problem: red Standby LED on, screen off, nothing happens if I press the power button. The screen stays off.

    Solved by replacing the 3 capacitors "1000uF 10V" on the power board.
    Just those 3 capacitors replaced. Everything seems working fine now.

    Thank you!

    ReplyDelete