Author Topic: Repairing a monitor (LG 2242T)- bad cap?  (Read 435 times)

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Offline MyHeadHz

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Repairing a monitor (LG 2242T)- bad cap?
« on: February 27, 2019, 09:56:13 am »
This monitor has been squealing recently, and now it has to try a few times to start up.  I took off the back panel and there appears to be a bulged SMD capacitor.  The marking on it are below:

1NIJ
33
100v

There seem to be a lot of options for direct replacement online.  However, I was curious if I would be able to replace that with standard electrolytic caps since I have them around.  The only capacitors I have on hand are 50v.  Would I be able to wire two caps in series to get 100v?  If so, what capacitance would the caps need to be?

Or should I just get a properly rated cap? :)  I have never tried any SMD work, but I guess I could always give it a whirl.
« Last Edit: February 27, 2019, 09:59:48 am by MyHeadHz »
 

Offline MyHeadHz

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Re: Repairing a monitor (LG 2242T)- bad cap?
« Reply #1 on: February 27, 2019, 03:46:28 pm »
Well, I replaced that bad cap and the problem is exactly the same.  Does it mean that the cap isn't the problem, or is it some incompatibility with solid state vs electrolytic caps?



The sound seems to come from that large chip labelled "E2242t,"  which gets quite warm.  It looks proprietary and probably not available.

Any ideas I can try, or am I SOL? :'(
 

Offline magic

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Re: Repairing a monitor (LG 2242T)- bad cap?
« Reply #2 on: February 28, 2019, 07:31:59 am »
I might be superstitious but I would try shorter leads for less inductance. You can even convert it to SMD by spreading the leads apart horizontally to match the PCB pads and bending the remaining part in a sort of half-swastika pattern so that it stands straight and doesn't topple.
It should be a low ESR type too, not sure if this one is.
 
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Offline MyHeadHz

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Re: Repairing a monitor (LG 2242T)- bad cap?
« Reply #3 on: February 28, 2019, 11:53:31 am »
Well, I trimmed the leads and the problem still seems to be about the same, though it is probably actually less severe.

I decided to try what would happen if I took out that capacitor completely, and it was definitely worse.  The capacitor I used to replace the dead one was one from this series from NTE.  It doesn't appear to be a low ESR cap, so that would be the next step.

I reassembled everything to try it out in a normal setup with the new cap (back cover on, etc), and it was noticeably better overall than with the original dead cap.  The sounds are significantly quieter than before, especially compared to the cap-less setup.  The monitor seems to start up more reliably as well.

For a while there has been increasing "snow" or noise on the screen, especially in dark environments.  That appears to be completely gone now.  So, overall, it is good enough for me.  If it starts getting worse, I will spend the ~$10 or so to get a couple of these.  Thanks for the help!
 

Offline switch998

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Re: Repairing a monitor (LG 2242T)- bad cap?
« Reply #4 on: February 28, 2019, 12:10:29 pm »
You should probably replace that with a similar SMD cap. I use Panasonic FK usually, but you would want to match the specs of the original cap closely, so make sure you review the data sheets.

Also, recap the PSU while you are in there, since that is probably the root cause of your issue.
 

Offline MyHeadHz

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Re: Repairing a monitor (LG 2242T)- bad cap?
« Reply #5 on: March 02, 2019, 10:37:30 am »
Well, I was wrong.  It only worked before because it was warmed up.  The next day, it was back to several retries before it would start.

I googled around and saw on Dave's channel and realized that there were two boards- an SMD and a through-hole, whereas my monitor only had an SMD board.  Then it hit me... the power supply is separate.

I soldered some leads on the monitor and hooked up my power supply and everything worked fine.  So I sliced open both the wall wart and my finger to find a bulged cap in there as well.  I replaced that cap ("Su'scon" brand, 105c, 25v, 680mF- 10.3mm x 17mm) with a similarly rated one I had handy (chongx, 105c, 50v, 470mF), and it was just the right size to fit back in the wall wart for reassembly.  Everything seems to function perfectly well and silently now.

Would there be any issue with this cap being a bit lower capacitance?
« Last Edit: March 02, 2019, 10:56:12 am by MyHeadHz »
 

Offline fzabkar

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Re: Repairing a monitor (LG 2242T)- bad cap?
« Reply #6 on: March 02, 2019, 11:21:49 am »
Lower capacitance is not recommended (more ripple). The second cap looks bad, too.
 

Online charlyd

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Re: Repairing a monitor (LG 2242T)- bad cap?
« Reply #7 on: March 03, 2019, 08:29:11 am »
and the first one on the right is also not flat roof if the picture is ok?
 


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