37LH5000 Switches itself off

[Johnboy78]

Hi guys, got a 37" LG 37LH5000 it has a fault where you turn it on and you get the channel install box up, but straight away the picture gets dimmer in 3 stages from normal brightness to black screen, it does this 3 times then switches off.....any ideas? it will switch on again but does the same thing.

Have opened it up and looked at the caps on the power board but they all look fine....im puzzled, any help would be gratefull. Thanks

[tom66]

Re: 37LH5000 Switches itself off

Check the BLON and DIM signals from the main board. If you need more help, you will need to post pictures.

[Johnboy78]

Re: 37LH5000 Switches itself off

whats the process to check those tom?

[tom66]

Re: 37LH5000 Switches itself off

Pictures of the chassis and power supply and then we'll talk.

[Johnboy78]

Re: 37LH5000 Switches itself off

just doing it now

[Johnboy78]

Re: 37LH5000 Switches itself off

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[Johnboy78]

Re: 37LH5000 Switches itself off

[Johnboy78]

Re: 37LH5000 Switches itself off

[tom66]

Re: 37LH5000 Switches itself off

Can you get a closer shot of the top left connector in this photo, in particular the pin legend in black next to it.

[Johnboy78]

Re: 37LH5000 Switches itself off

yep will do it now

[Johnboy78]

Re: 37LH5000 Switches itself off

[tom66]

Re: 37LH5000 Switches itself off

I can't really see those, any way you can get better focus?

[Johnboy78]

Re: 37LH5000 Switches itself off

i will try, my camera isnt the best lol, or i could write them down probably be better

[tom66]

Re: 37LH5000 Switches itself off

Writing them down would work too.

[Johnboy78]

Re: 37LH5000 Switches itself off

best i can do!

[Johnboy78]

Re: 37LH5000 Switches itself off

the top right is PWR-DTM, then underneath that is ERROR INV ON/OFF

[tom66]

Re: 37LH5000 Switches itself off

OK, it looks like the 2nd down from top left pin is the backlight brightness control.

You will need a digital multimeter.

Set the multimeter to DC 20V. Red probe goes in VOLT jack. Black probe in COM jack. Place the black probe on some exposed part of the metal backing, e.g. the wall mount points. Then touch the red probe to the exposed metal around the connector. The connector to the main board must be installed.

Record the reading when the TV is working, then as it begins to get dimmer and finally when it switches off.

[Johnboy78]

Re: 37LH5000 Switches itself off

hmm ok ill have to get a voltmeter from somewhere. Have u got any ideas what it might be?

[tom66]

Re: 37LH5000 Switches itself off

If the BRI signal is not stable it is the main board, but if it is stable it is power board, inverter board or lamps. Likely inverter board or lamps in my opinion.

[Johnboy78]

Re: 37LH5000 Switches itself off

ok is it possible to test the inverter board and power board too?