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Old 02-02-2022, 10:45 AM   #41
Diah
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Default Re: LG 70UH6350 Mainboard issue

sorry i did mistake.. Tuner related to 12V rail
only DCDC 5V normal /USB & Audio Amp
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File Type: jpg DCDC.jpg (104.0 KB, 9 views)
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Old 02-02-2022, 10:56 AM   #42
Storyteller12
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Default Re: LG 70UH6350 Mainboard issue

Did some more testing and found this coil L2307 shorted to ground. Iím removing now to see if it clears the shorts on the smd caps.
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Old 02-02-2022, 11:17 AM   #43
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Default Re: LG 70UH6350 Mainboard issue

Thanks Diah, I found both shorted. However it’s not shorted to ground.

I’m removing them now to test
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Old 02-02-2022, 11:21 AM   #44
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Default Re: LG 70UH6350 Mainboard issue

Sorry, I was thinking they were caps. that why I thought they were shorted. They just have continuity.
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Old 02-02-2022, 11:24 AM   #45
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Default Re: LG 70UH6350 Mainboard issue

if you mean on the one you marked ,, C730 its labeled DUMMY will read short LOL

look on the L i remarked to you before.. open them one by one the 24 will back to normal i suspect DCDC so start with it.
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Old 02-02-2022, 11:27 AM   #46
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Default Re: LG 70UH6350 Mainboard issue

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Originally Posted by Storyteller12 View Post
Sorry, I was thinking they were caps. that why I thought they were shorted. They just have continuity.
they are the internace of 24V to DCDC and Audio AMP. one by one need to take out and turn on check your 24V back to normal.
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Old 02-02-2022, 11:41 AM   #47
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Default Re: LG 70UH6350 Mainboard issue

Ok. I took each one out and still tested 27v. However I did replace the one I took out first l5800 before taking the second one out of circuit l2038. After I remove l2038 I did get red light on optical audio port
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Old 02-02-2022, 11:43 AM   #48
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Default Re: LG 70UH6350 Mainboard issue

Also still have shorted smd caps with l2038 out
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Old 02-02-2022, 11:47 AM   #49
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Default Re: LG 70UH6350 Mainboard issue

you said the Optical work now... are you sure the 24V still high?
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Old 02-02-2022, 12:01 PM   #50
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Default Re: LG 70UH6350 Mainboard issue

keep L2308 out from boards... you need to test this 2 zener zd2303 zd2300

dont give any attention on c703 its dummy. mean both pins connected together
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Old 02-02-2022, 12:59 PM   #51
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Default Re: LG 70UH6350 Mainboard issue

Quick update. The L2038 is measuring 11.77v so that’s not tied to the 24v.

I did test the zener diodes

Zd2300 measure 592 one way and 409 the other way.

Zd2303 shorted together one way reading 043 and 081 the other way but not shorted
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Old 02-02-2022, 01:01 PM   #52
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Default Re: LG 70UH6350 Mainboard issue

Also I made a mistake by plugging in the tcon each time I powered on. After unplugging that completely I got the 24v down to 25.3v.

So I’m guessing the tcon is bad also but is the 25.3v is still high correct.
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Old 02-02-2022, 01:02 PM   #53
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Default Re: LG 70UH6350 Mainboard issue

Another note the optical audio doesn’t always light up. If I completely unplug it from the power supply it will light up. But if I just power down from the remote and power back on it doesn’t light up.
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Old 02-02-2022, 01:17 PM   #54
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Default Re: LG 70UH6350 Mainboard issue

because we dont have the service manual... if L2308 12V rail then look on other circuit IC and its L most time will have same NO, from yours OP photo i cant see it very well--
if you removed the T-CON .. T-CON took Panel VCC from 12V, rail,
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Old 02-02-2022, 04:17 PM   #55
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Default Re: LG 70UH6350 Mainboard issue

All the ic circuits with L that measured 25v I removed but unfortunately none seems to solve the problem and bring voltage back to 24v. Might have to throw the towel in on this one for now and hope to find a used board in the future
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Old 02-02-2022, 05:34 PM   #56
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Default Re: LG 70UH6350 Mainboard issue

Having 25v on the 24v supply is not your problem, that 24 volt supply is not regulated that close and if the tv is not operating there will be very little load on that supply so the capacitors will charge to a slightly higher voltage.

When you tried the other main board and had backlights, did you also get an image on the screen? ie menu

Last edited by R_J; 02-02-2022 at 05:37 PM..
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Old 02-02-2022, 06:33 PM   #57
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Default Re: LG 70UH6350 Mainboard issue

I can’t test the image because it’s a slightly different main board and doesn’t match the tcon. The power supplies are the exact same so I knew it would work to test the backlights.
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Old 02-02-2022, 06:34 PM   #58
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Default Re: LG 70UH6350 Mainboard issue

Quote:
Originally Posted by Storyteller12 View Post
Quick update. The L2038 is measuring 11.77v so thatís not tied to the 24v.

I did test the zener diodes

Zd2300 measure 592 one way and 409 the other way.

Zd2303 shorted together one way reading 043 and 081 the other way but not shorted
These readings don't seem right, I would take them out of circuit and test them again, unless there's a reason for those readings.
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Old 02-02-2022, 07:36 PM   #59
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Default Re: LG 70UH6350 Mainboard issue

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Originally Posted by nomoresonys View Post
These readings don't seem right, I would take them out of circuit and test them again, unless there's a reason for those readings.
My 12v tested fine and that circuit is tied to the 12v rail so Im just assuming that those diodes are fine. I would like to find what is shorting all the smd caps and the 1 ic I mentioned a few post back. Since I donít get backlights Iím guessing itís something on that part of the circuit.
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Old 02-03-2022, 06:58 AM   #60
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Default Re: LG 70UH6350 Mainboard issue

https://www.youtube.com/watch?v=XhqwC3BFBug
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