Hyundai B91a (backlight Problem )

[garrymc123]

Hi there all her is a another Little project of mine that i could do woth some professional advice i got this monitor of a friend . here told me that it turns of after half a hour. when i got it home i pluged it my pc and sure enough i turned of but its just the backlight that is turning of. so i opened it up checked the inverter board but no obvious signs so i checked the capacitor with a meter and it was supposed to be ( 25v 470uf ) but it read 510uf so i replaced it thinking that was the problem. so i put it back together and it still done the same thing. so i thought it must be a heat problem. so i pulled out the hair dryer and when i blew it over the board sure enough the back light cut out and i also did this in a dark room because i could here a crackling noise when it was cutting out to see if i could see a spark or something but couldent see anything

here are some pics






hope someone can help me resolve this problem ie what components to check

thank you

[NxB]

Re: Hyundai B91a (backlight Problem )

whats under the green board

[Krankshaft]

Re: Hyundai B91a (backlight Problem )

Check for bad solder joints crackling is probably arcing.

That green board should be removed and checked too I'm betting it contains the PWM for the inverter. No idea why they would mount it like that though.

[Krankshaft]

Re: Hyundai B91a (backlight Problem )

Check for bad solder joints crackling is probably arcing.

That green board should be removed and checked too I'm betting it contains the PWM for the inverter. No idea why they would mount it like that though.

Hopefully the IC isn't one of those epoxy blobs and that's why there is a separate board.

[EGuevarae]

Re: Hyundai B91a (backlight Problem )

That green board should be removed and checked too I'm betting it contains the PWM for the inverter. No idea why they would mount it like that though.

I've seen that in several Samsung Units. It's like a board by it's own.

[garrymc123]

Re: Hyundai B91a (backlight Problem )

Thanks guys for the advice i have removed the small green circuit board
but can,t see anything of the obvious.

small circuit board pic



where is the pwm so i can check it or any other connections or components to test.

thanks

[mcfischer]

Re: Hyundai B91a (backlight Problem )

I think you should sub the backlights and try the heat test. Your symptoms steer me toward suspecting weak bulbs or bad connections to the bulbs. Reminds me of the Dell 19" model that would work for a long time then shut off the backlights. Cycle power and it works again for a while, sometimes for a shorter time until shut down. All cured by replacing backlights.
Mike