37LH5000 Switches itself off

[tom66]

Re: 37LH5000 Switches itself off

Check BRI on new board. You could have a dud main board...

[Johnboy78]

Re: 37LH5000 Switches itself off

no it does the same as the old board so obviously isnt the fault.

[Johnboy78]

Re: 37LH5000 Switches itself off

what else can i test?

[tom66]

Re: 37LH5000 Switches itself off

no it does the same as the old board so obviously isnt the fault.

...or the board you got is faulty?
But let's for now assume it is OK.

Can you get hold of some 470 ohm resistors?

[Johnboy78]

Re: 37LH5000 Switches itself off

cant unless maplins sell them? wat did u have in mind?

[tom66]

Re: 37LH5000 Switches itself off

Maplins will sell them.
Forcing PSON, BLON and BRI high and testing backlight.

If the screen stays lit, the problem must be on the main board.

[Johnboy78]

Re: 37LH5000 Switches itself off

Personally i think the main board is fine, its highly unlikely both main boards new and old would have the same fault?

[tom66]

Re: 37LH5000 Switches itself off

Personally i think the main board is fine, its highly unlikely both main boards new and old would have the same fault?

You know... I used to think this. I mean, what's the chance?

But quite often, a particular model only has one or two common problems.

And these boards come from smashed screen sets.

But consider this: Your TV has stopped working properly, but you determine that hitting it makes it work (perhaps it doesn't, but you think it does because it's hard to correlate.) And then one day you hit it too hard. Oops, the screen breaks. So you drop it off at the dump.

TV scrap guys pick up a TV (if it doesn't get crushed for metal first), strip it out, and sell the parts. No testing is ever done.

[Johnboy78]

Re: 37LH5000 Switches itself off

i guess so, but how far do u go. do u keep buying the same part and get the same part everytime only to find it faulty or so u think lol, u could never get to the bottom of it unless u had a completely working tv the same and swap out each board till u get the right one.

[tom66]

Re: 37LH5000 Switches itself off

Well, yeah, but there's only one board that controls the LCD brightness via BRI, and that is the main board. Unless LG have done something silly like feed it from the T-con, but I can't see that happening.

[budm]

Re: 37LH5000 Switches itself off

If you disconnect the BRI line from the main board to the inverter board and use 1K resistor between the BRI pin on the inverter board and 5V, and another 2K between the BRI pin and ground which will give BRI PIN 2/3 of 5V feeding the BRI pin. If the backligts stay on steady then the inverter is OK.

[Johnboy78]

Re: 37LH5000 Switches itself off

Just to let u know it was the inverter board at fault. Board replaced and working fine now.

[tom66]

Re: 37LH5000 Switches itself off

I am surprised by this eventual conclusion.

[Johnboy78]

Re: 37LH5000 Switches itself off

No doubt! I thought i would post it up anyway at least its abit of info for you too in case u see anyone else with the same fault in the future lol

[primoz1]

Re: 37LH5000 Switches itself off

Hi. I've got same board from LG37LH4900 but I dont have any voltage no where on the board, except 220 v on the power line and on the Transformer after that stage is no more than 0.09v just for few moments and drop.