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Repair guides and support for your LG TV.

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LG OLED tv, intermittent black screen

Block Image

Update: I took the back cover off, and cleaned all the connectors between boards, and then reconnected everything. I turned it on and it the picture came up as it should! I put it all back together and hung it back up, turned it on and... total black screen. Bummer.

55" LG OLED tv

Intermittently - about 95% of the time at this point - when turning on the tv everything works except the screen is totally black. No picture, no menus, nothing. Sound works fine, you can still change channels and adjust the volume with the remote. When the picture does work there is no sign of any defects, everything looks perfect. I've done all the reset sequences and tried the backlight tests with a flashlight (that failed). Any ideas? Maybe reseat some internal connectors? Thx.

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Hi @jamesfriend

What is the model number of the TV?

OLED (Organic Light Emitting Diode) TVs don't use separate LED backlights to light the screen.

The OLED pixels in the screen create their own light, that's why the flashlight test is no good on OLED TVs.

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@jayeff Well that would explain why the test failed then! I added a picture of the label on the tv above, it has the model info. Thanks!

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My Oled TV OLED55C8PVA is currently going through same issues. It went sleep mood but won't on when I try oning it as have tried all means to out it back on but won't on.

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Hi @jamesfriend

Can't find any service info on your model but here's some info from the 55C9PUA service manual that may help.

I linked it because both TVs use the same power board and whilst the mainboard is different I'm thinking that the flowchart linked above will still help.

Check if the voltages shown in the flowchart going from the power board to the mainboard and the voltages from the power board to the "module" (LG name for the screen) are OK.

Here's where to find them on the power board

Depending on what all the voltages are will determine what the problem is i.e. power board to module voltages OK = replace the screen, not OK = replace power board, power board to mainboard voltages OK = replace mainboard, not OK = replace power board.

You can try the Vx1 lock voltage check (see p.44) but since the mainboard is different to the one in your model, the test points may not be the same.

Since the power board is common to both TVs then the voltages (and connector pins test points) are the same. Worth trying anyway.

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Thanks much jayeff, I'll dig out my meter and give this a shot this weekend.

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Hi jayeff - A rookie question, forgive my ignorance: in looking at the diag steps I see things like "check voltage at R7624", with no hint at to 1. which side of the resistor to check, and 2. what is that voltage referenced to? A common ground?

Thanks!

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@jamesfriend

Voltage is always with reference to ground unless specified otherwise.

Initially measure either side of the both of the resistors and compare their values.

Looking at the description if R7624 is low then R7632 should be also if Vx1 is locked OK

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Hi jayeff - Closing this thread out. Sorry it took so long to get back on this, but the tv project got moved aside for an emergency house repair. When I got back to it, the diagnostic references you sent were invaluable. Yes, the power supply was identical to the one in the manual, and the layout of the main board was close enough that I could determine the Vx1 wasn’t the issue. Being an intermittent problem, it took a while to get the tv to fail on the bench, but once it did I was able to determine the power supply board output voltages were not correct. I found an “open box” power supply board on eBay for $100 (really a take off from a tv whose screen had been damaged in shipping). Got that installed and have been running it off an on for a couple days now and it appears to be fixed!

Thanks very much for the assistance, saved me a bunch of money and prevented a big tv ending up in a landfill somewhere.

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