Is Repairing an LCD Monitor Feasible?

Discussion in 'Odds & Ends' started by Bud, Dec 30, 2009.

  1. Bud

    Bud Bionic Poster

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    I just replaced my top of the line, 3 year-old, 21" Samsung LCD monitor with a new 24" Samsung LCD... due to a power/backlight issue.

    For the last few months, it required a short warm up period... or else it would click off. So, I'd turn it on (the backlight would shut off after 3-4 seconds) and leave it on for a couple minutes (with the backlight off). Then, I'd quickly turn it off then back on at, which point it would stay on. To solve this, I never turned the power off... just used a screen saver.

    To make a long story short... it somehow got turned off and I could not keep it on after that (even with the previous warm up routine). It would stay on for 10-20 seconds and then the backlight would turn off (even though the blue power light was still illuminated on the front bezel).

    To anyone with experience troubleshooting/repairing LCD monitor issues... Is this worth fixing?
     
    #1
  2. cucio

    cucio Legend

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    From the symptoms you describe I'd definitely check out the inverter. It normally takes the form of a longish circuit board, the size of a pen, with one connector at each end, and contains a very characteristic part, the transformer. If the connectors or the board have burn marks, it is well worth trying to replace it.

    You can buy a new one in the bay for something like $10 and it is a very easy operation, more or less like replacing a faulty RAM stick from a PC.

    [​IMG]
     
    #2
  3. cucio

    cucio Legend

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    Oh, and one thing...


    MAKE SURE YOUR MONITOR IS UNPLUGGED BEFORE YOU OPEN IT
     
    #3
  4. Bud

    Bud Bionic Poster

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    Thanks Cucio! Will give it a try... not much to lose at this point :)

    I made the mistake, many years ago when workin inside an Apple II+... of fiddling around while it was still plugged in. I accidentally touched the power supply (which was completely exposed on those first generation PC's) :twisted:

    I was only 11 or so and learned a valuable lesson.
     
    #4
  5. Bud

    Bud Bionic Poster

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    I've got it all pulled apart but don't see anything that resembles the pieces above :oops:

    I'll take a pic of the innards and post it a bit later :)
     
    #5
  6. Bud

    Bud Bionic Poster

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    Innard Pics

    [​IMG]

    [​IMG]
     
    #6
  7. cucio

    cucio Legend

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    Argh, sorry, I talked off my ass :oops:. Apparently that kind of inverters is only found in laptop LCDs, to generate the high voltage necessary to power up the backlight from the low voltage supplied by the battery. I guess in monitors this comes directly from the power supply circuitry. That and replacing broken LCD panels are the only LCD repairs I have direct experience with, and always with laptops.

    I guess the main suspects are then the backlight itself and the circuitry that powers it, probably the former, since there doesn't seem to be any obvious burn marks.

    There are message boards for this kind of stuff out there, they usually pop out soon enough in Google searches.

    Edit: anyway it is a fluorescent light bulb, so there should be an inverter somewhere, maybe integrated in the power supply, perhaps those two transformers at the left with the white and cyan wires coming out of them. Are there two light bulbs, one at the top and other at the bottom?
     
    Last edited: Dec 31, 2009
    #7
  8. jmnk

    jmnk Professional

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    your problem is either the inverter (as cucio suggests) or the backlight. The inverter is usually quite easy to replace. You just need to google (or search on ****) for 'inverter for --your LCD name here--). You can/should also search by any of the serial numbers you have on those white labels. It takes try and error, if you are lucky someone may post a picture of exactly same LCD as yours with inverter part number listed.
    However the problem is that there's no easy way to tell if maybe it is the backlight. You should have long thin white tubes running along the edge(s) of the lcd. It looks from the pictures like they will be running along top and bottom edge. These are harder to replace, you need to be extra careful not to touch/destroy any of the flex connectors attached to lcd screen. Frankly I've tried this a few times with various luck. On the other hand there's not much to lose - so again google for 'backlight for --your LCD monitor here--'.
    You may also try to replace the entire LCD panel (so your power supply, connectors, etc stay). Regardless of the brand of your monitor the panel itself likely comes from a well known vendor - so search by one of these white labels serial numbers, **** should have some.
     
    #8
  9. Bud

    Bud Bionic Poster

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    Thanks... will give it a try before closing it up and ditching it (assuming I don't succeed) :)
     
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  10. Bud

    Bud Bionic Poster

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    BTW, I did find out the issue and have the parts on order. It appears that 3 of the electrolytic capacitors are fried (common problem). I have to de-solder the old parts and then re-solder in the new parts. Hopefully, it will work once completed.

    I'll post a pic of the bad parts, when I get a chance :)
     
    #10
  11. Bud

    Bud Bionic Poster

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    The problem

    Look at the pic below. The capacitor tops should be flat like those pointed to by the green arrow. When they blow, the contents basically push out the top... which is why the bad capacitors, pointed to by the red arrows, are bulging.

    Therefore, the 3 bad capacitors with the bulging tops must be de-soldered, removed and then replaced.

    [​IMG]


    Bulging Capacitors (below)

    [​IMG]
     
    Last edited: Jan 11, 2010
    #11
  12. Bud

    Bud Bionic Poster

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    Woohoo! Success...

    After de-soldering the 3 bad capacitors, then re-soldering in the new ones... the monitor works just like new :)
     
    #12
  13. cucio

    cucio Legend

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    Good job! Many perfectly functional devices stop working because of electrolytics aging. That nasty stuff they have inside is pretty corrosive. Shorted trafos are common suspects, too.

    I love to repair things, throwing away stuff which can be mended with little effort makes my little green heart bleed.
     
    #13
  14. Bud

    Bud Bionic Poster

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    That's the only reason I opted to fix this, as well! I figured if I can repair it for a few dollars and learn something in the process... rather than just tossing it into the garbage pale, it would be well worth it. Amazing how a few dollars (parts and shipping were 8-9 dollars total) in electronic parts can end up making a whole lot of waste. The monitor is just like brand new, now.

    Perhaps someone else in the future will run across this thread and opt to fix their LCD monitor rather than just trash it. I've heard 90% of these LCD repairs are simply replacing inverters or capacitors.
     
    Last edited: Jan 15, 2010
    #14
  15. jim e

    jim e Hall of Fame

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    Nice job Bud! I have a problem with my monitor as well. I just died on me. Mine will not power up at all, not even a green light to tell you its powered up, as if the unit was unplugged. I checked the fuse by temp bypassing it, and that was not the problem. Any thoughts on what may be the problem with symptoms like this?Otherwise its just going in the trash, if there is a possible solution,I would give it a try.
     
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  16. Bud

    Bud Bionic Poster

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    Did it give you any indication of a problem prior to breaking? If you can, pull it apart and take pics of the inside like I did with mine.

    When you get it apart, it should look similar to what's in post #6

    If you're going to trash it... advertise it on CL for free or see if a monitor repair shop will take it. That way, they can fix it on their dime and it won't be heading to a landfill. After researching it... many monitor repairs on these LCD's are very inexpensive... and just require some time, 2-3 dollars in parts and a small soldering tool.
     
    Last edited: Jan 15, 2010
    #16
  17. jim e

    jim e Hall of Fame

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    There was no indication of any failure, it just stopped, like someone unplugged it.If all esle fails, your idea to give it to someone who can make use of it is a great idea, thanks.
    Here's a picture of it. The caps look okay, at least they are not raised like yours, they all seem flat. My first thought was a fuse, so I removed the fuse, and temp. jumped it to bypass it, and it made no difference.

    [​IMG]
     
    Last edited: Jan 15, 2010
    #17
  18. Bud

    Bud Bionic Poster

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    Are the capacitors located in the upper left side of the picture also flat? Does there appear to be anything leaking out the bottom of any of them? Sometimes, they'll leak as opposed to puffing up on top.

    It sounds like it could be the power supply. Not sure how hard/expensive that is to fix but perhaps someone else who knows will chime in.

    I'm wondering if you take one of those live wire testers (with the little light) and touch a lead after the power supply... you can at least diagnose if it's the power supply or not.
     
    Last edited: Jan 15, 2010
    #18
  19. jim e

    jim e Hall of Fame

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    yes, the left side ones are flat as well, and no signs of leakage. you are prob. correct, something with the power supply.
     
    #19
  20. David_Is_Right

    David_Is_Right Semi-Pro

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    Nice job on the repair!
     
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  21. Polaris

    Polaris Hall of Fame

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    Good work, dude! That is inspirational, in this age when there is so much incentive to just throw things away when they stop working.
     
    #21
  22. cucio

    cucio Legend

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    Let's start with the obvious. Are you sure there is voltage in your wall outlet? If it is not a fuse, then maybe a loose/broken wire somewhere? Tried another power cord? Power circuits are normally quite easy to diagnose with a multimeter if you know your electronics.

    Another easy repair worth a try is going over solderings that may have gone cold with a "soderling" iron. (lol, I have seen people here misspell Soderling as Soldering, so I thought I might as well counter-attack.)

    Once my GF's CRT (yeah, bulky, power wasting CRTs are still useful if you are a digital photographer and need calibrated colour fidelity) was flickering. Apparently some components in the horizontal deflection circuit get too hot to the point they may melt the nearby soldering paste, leading to loose electrical unions. You could see mild scorch marks and matte soldering points. I just went over the whole section of the board remelting the paste and pop went the flicker.
     
    #22
  23. Bud

    Bud Bionic Poster

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    Thanks! Now... what do I do with the extra monitor :-? :grin:

    I agree about checking the obvious... as I once had a power cord that went kaput! Someone suggested I check and sure it enough... it was the power cord :)
     
    #23

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