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Old 01-21-2020, 05:40 PM   #1
aquele
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Default Lg flatron l1917s

Hey guys/girls,

I have an old LG L1917S which doesn't work (doesn't turn on nor the LED turns). I would like to repair it (as a project and to learn more, since it is an old LCD monitor).

I started by opening it, separate the power supply (AIP-0108) and the controller and check the power supply. The power supply seems to be all okay (fuse was ok, capacitors seem ok - C0204 can have a little bulge, not sure). Then i measure the outputs from the power supply (between GND and the pin). 5V had 4.998V (ok!) and 12V had 17.84V (it seems a value too high, but from what i read in other posts here in the forum, the 12V is not regulated without the controller connected - https://badcaps.net/forum/showthread.php?t=62426, so i guess this value is correct - correct me if i'm wrong).

Everything seemed ok. I then connected the controller to the power supply and something very strange happened. Measuring the 5V i now had 0.178V and the 12V rail was constantly decreasing in value from the 17.84V. When disconnecting the controller from the power supply, the problem persisted. If i disconnected the power supply from mains (230V) and reconnected (without controller) i had 5V and 17.84V, again, in the power supply's pins.

From what i have seen, the main problem from power supplies are the capacitors. My problem seems a capacitor problem? Also, can i use capacitors rated for 25V in my 5V rail (in the 5V rail they are rated to 16V and in the 12V rail for 25V)? I don't know any reason why not to use, but since i don't understand much about this system (power conversion).

Best regards
Attached Images
File Type: jpg controllerB.jpg (93.5 KB, 7 views)
File Type: jpg controllerF.jpg (111.4 KB, 12 views)
File Type: jpg powerSupplyB.jpg (138.5 KB, 8 views)
File Type: jpg powerSupplyF.jpg (110.9 KB, 17 views)

Last edited by aquele; 01-21-2020 at 05:45 PM.. Reason: Images as an attachment
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Old 01-21-2020, 05:47 PM   #2
petehall347
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Default Re: Lg flatron l1917s

one looks swollen change those 4 .
its ok to go over voltage .but never go lower unless you know its ok for that particular circuit .
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Old 01-21-2020, 06:00 PM   #3
aquele
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Default Re: Lg flatron l1917s

Quote:
Originally Posted by petehall347 View Post
one looks swollen change those 4 .
its ok to go over voltage .but never go lower unless you know its ok for that particular circuit .
Yeah, that was what I know from electronics but is better to confirm with the specialists

Which 4 are you talking about? The ones inside the red square?
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Old 01-25-2020, 04:50 AM   #4
petehall347
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Default Re: Lg flatron l1917s

yes . might be best change those other 2 as well
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Old 01-25-2020, 11:40 AM   #5
R_J
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Default Re: Lg flatron l1917s

I would also change the 2 small electrolytics in the primary while you have it apart, these two primary caps won't show any bulging or leaking but just dry out over time.
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