Mulja tv repair portal

Equipment Repairs => LCD TV forum => Topic started by: xerian on July 13, 2018,10:40:10

Title: LG 42LD751 red LED blinking with all voltages present
Post by: xerian on July 13, 2018,10:40:10

Hello. I have a LCD TV LG 42LD751 sitting in my storage room for a year now. Now I get a smaller version 32 inch with exactly same simptoms. So with two of them I need your help guys.
With power on LED blinks slowly and it can blink indefinitly ( left it over night) Electrolyts are good.
All voltages are present on powerboard. PSON is 3,3V, 3,3V present, 5V present, 12V present and 24V present. Only 24V is litle higher than 20V. I suspect that something on 24V rail is at fault that inverter could not come on. I've searched this forum for similar faults and only find one post that mainboard could be at fault. Is that possible even if the PSON comes on?

Best regards
Danilo

Title: Re: LG 42LD751 red LED blinking with all voltages present
Post by: Turnip on July 13, 2018,11:01:05

Hi Exerian,

Seems the SSB can be cooked in the oven (180C for 10 Minutes) where issues are mostly resolved.

Done it several times but - Ovens have a mind of their own so use a clip on thermometer, and when temperature gets to 200C, turn oven off and insert the SSB.

First time, I relied on the cooker thermostat where chips fell off, second time the Scart sockets melted so had to replace them.

Otherwise, seems to work well - Chris.

Title: Re: LG 42LD751 red LED blinking with all voltages present
Post by: downunder on July 14, 2018,03:55:43

Hi Exerian,

A lot of LGs seem to suffer from the "INV" voltage missing (that's the Backlight-ON signal) and originates from the main board and is fed to the PSU.

If this is missing, then yes, cook the main board as Chris suggests. I preheat to 180 and leave the oven on for 10 min. Then open the door and let the

board cool naturally before moving it. Works for me.                             Bruce

Title: Re: LG 42LD751 red LED blinking with all voltages present
Post by: xerian on July 17, 2018,03:22:47

He he. Old fashion oven repairing. Reminded me on our graphic card cooking decade ago. Now I have BGA so Will try this way.
Does enyone know what chip is in question for this failure?
Probably I don't have stencils for this LG chip so even with BGA present, oven would probably be my best solution.
Thanks guys

Title: Re: LG 42LD751 red LED blinking with all voltages present
Post by: downunder on July 17, 2018,05:00:24

Hi Danilo,

It'll be the main microprocessor - the one with the heatsink affixed.