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Old 12-28-2021, 01:25 AM   #1
Super360
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Default LG 37LC50C Turns on then off

I have a lg tv here that is one of those commercial tv units. It will power on make a staticky sound then shut off. It does display a picture then it just shuts off what can I do? The psu has good standby voltage as well. I'm wondering if the lamp is dead possibly?
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Old 12-28-2021, 02:59 AM   #2
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Default Re: LG 37LC50C Turns on then off

I think the motherboard has a issue because when I was probing the psu connector accidentally shorted ps_on with 5v standby and it kicked on no issue. I imagine some bga/capacitor issue on mainboard. I'm buying a new motherboard and will report back.

Last edited by Super360; 12-28-2021 at 03:09 AM..
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Old 01-01-2022, 03:24 AM   #3
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Default Re: LG 37LC50C Turns on then off

So I replaced the motherboard to have it do the same thing now I'm thinking it's the backlight inverter is there anyway to test these things.
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Old 01-01-2022, 05:44 AM   #4
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Default Re: LG 37LC50C Turns on then off

Did the backlight work with the ps-on test?

Report the voltages on the inverter cable, 24V and bri, dim and the other two.
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Old 01-01-2022, 06:02 AM   #5
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Default Re: LG 37LC50C Turns on then off

Yes the backlight turns on with ps_on test.
ADC= 4.18V
ON/OPFF= OFF MODE=0.0051V DC 2.74V IN ON MODE
5T5V=5V
5T5V=5V
5V= 0.500V
3.4_ON= 2V WHEN POWER IS ON 0.055V WHEN OFF
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Old 01-01-2022, 06:16 AM   #6
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Default Re: LG 37LC50C Turns on then off

18V=18V WHEN POWER IS PRESSED ON. 7v when power is off
18v=18V WHEN POWER IS PRESSED ON. 7v when power is off
6v= 6when power is on 0.700v when power is off
3.4v= 3.5v when power is on 0.700v when power is off
12v= 1.300v when power is off 12 volts when power is on
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Old 01-01-2022, 06:24 AM   #7
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Default Re: LG 37LC50C Turns on then off

dim=3.3v when power is on 0v when off
i-c=5v when on 0v when power button is off
bri= 1.69v when on 0v when off
All the 24v are 24v when the power button is pressed on 0v when off
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Old 01-01-2022, 07:02 AM   #8
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Default Re: LG 37LC50C Turns on then off

The voltages are fine except for the 5V pin. You must have noticed that too, Now I do not know if it's actually used by the TV, since there's 6V going to the mainboard, trace to find its source on the PSU board.

If the backlight stays on during the ps-on test it's not the inverter, the signals (bri, i-c, dim) that the mainboard is sending are normal.
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Old 01-01-2022, 07:13 AM   #9
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Default Re: LG 37LC50C Turns on then off

Ya I cancelled the inverter theory and now I'm just gonna chuck a used psu into it.
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Old 01-01-2022, 07:49 AM   #10
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Default Re: LG 37LC50C Turns on then off

service manual if needed
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Old 01-01-2022, 08:30 AM   #11
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Default Re: LG 37LC50C Turns on then off

I bought a repair kit for this psu. https://www.ebay.com/itm/tkit28-LG-3...-127635-2958-0
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Old 01-01-2022, 08:38 AM   #12
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Default Re: LG 37LC50C Turns on then off

Quote:
Originally Posted by Super360 View Post
I bought a repair kit for this psu. https://www.ebay.com/itm/tkit28-LG-3...-127635-2958-0
i think these repair kits only have 6 capacitors in them fixes
SLOW START UP
STUCK IN STAND BY

C204
C205
C221
C222
C223
C232

Last edited by vinceroger69; 01-01-2022 at 08:41 AM..
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Old 01-01-2022, 11:38 AM   #13
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Default Re: LG 37LC50C Turns on then off

Well seeing as how you made it easy I opted to just buy the caps outright instead much cheaper.
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Old 01-01-2022, 12:59 PM   #14
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Default Re: LG 37LC50C Turns on then off

Quote:
Originally Posted by Super360 View Post
Well seeing as how you made it easy I opted to just buy the caps outright instead much cheaper.
How i usually find whats in the repair kits and location of parts is too look on ohm supplies web site, kit kit103 is for your psu (good company i have used them a lot here in the uk)
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Old 01-01-2022, 01:04 PM   #15
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Default Re: LG 37LC50C Turns on then off

LOL I was like how did this mf find all these capacitor values. I was searching through the listing trying to find what you saw lol thank you man. Will give ya guys a update when these low-esr ebay special arrive.

Last edited by Super360; 01-01-2022 at 01:06 PM..
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Old 01-03-2022, 10:46 AM   #16
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Default Re: LG 37LC50C Turns on then off

Looking forward to learning what worked/didn't work. Good luck!
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Old 01-17-2022, 03:51 AM   #17
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Default Re: LG 37LC50C Turns on then off

Well update replaced all those caps to have it keep doing the same thing damn.
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Old 01-17-2022, 03:57 AM   #18
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Default Re: LG 37LC50C Turns on then off

I think either the screen or the tcon or something I don't know bout to toss it.
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Old 01-17-2022, 04:07 AM   #19
vinceroger69
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Default Re: LG 37LC50C Turns on then off

does the backlight flash on and off i wonder if this is a 2 second too black fault as ccfl set

ignore the above, i see you can trick the backlight to stay on so not that.

Last edited by vinceroger69; 01-17-2022 at 04:09 AM..
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Old 01-17-2022, 04:10 AM   #20
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Default Re: LG 37LC50C Turns on then off

One of the first and least expensive things you can do when you have an issue is take the powerboard out of the tv, flip it over and look the solder joints over with a magnifying glass if needed, add a little flux to make the solder flow well and add solder to any joints that look even a little suspect. You can practice on a scrap pcb board if needed, careful not to bridge any joints, and always let the board sit for quite a while or discharge the big caps with an appropriate resister before working on it (safety first) to try to keep from getting shocked, it doesn't take 1000 volts to KILL, a lot less can kill, so be careful, it's only a tv.
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