Proscan PLDED3996A led backlight help

[tom66]

Re: Proscan PLDED3996A led backlight help

What does pin ON/OFF read with multimeter black on chassis, red on that pin?

[boxingfan]

Re: Proscan PLDED3996A led backlight help

3.5v with tv on, thanks

[boxingfan]

Re: Proscan PLDED3996A led backlight help

3.5v with tv on, thanks

Is that reading ok?

[tom66]

Re: Proscan PLDED3996A led backlight help

That reading indicates main board is switching on LED backlight. So fault is with PSU or backlighting.

Can you remove the power board carefully (turn TV off for 30 minutes - unplug at wall - before doing this) and take pictures of the bottom of the board?

[boxingfan]

Re: Proscan PLDED3996A led backlight help

this is the back of the psu, is this what you want? thanks you i know is not fun to help a dumb guy like me

[tom66]

Re: Proscan PLDED3996A led backlight help

Need a clearer photo of top left of this board - ideally with consistent lighting and sharper focus.
https://www.badcaps.net/forum/attach...5&d=1391989814

One tip with board photos: taking a board out into pure sunlight can help. Try using macro photos. If you have a smartphone or camera with tap to focus, tap on a large dark object with contrasted edges, like the device in the top left, to help improve photos. I am able to get super-sharp photos with a Galaxy S2... which is nearly 4 years old and only 8 MP sensor.

[boxingfan]

Re: Proscan PLDED3996A led backlight help

any better? im using an iphone 4 that i know doesnt have the best camera, if not ill get a better camera and sunlight tomorrow, thanks

[tom66]

Re: Proscan PLDED3996A led backlight help

I will try and come up with a response tomorrow (too late right now), but if I happen to forget, please reply again. Photos look usable enough to understand circuit, but I will ask for part #s in trying to decode it.

[boxingfan]

Re: Proscan PLDED3996A led backlight help

thank i just noticed that i took pics of the top right, here is what you ask me, thank you, yea it is late for you (uk) i,m at -5 GMT, so see you tomorrow ill bump this thread

[boxingfan]

Re: Proscan PLDED3996A led backlight help

Bump

[boxingfan]

Re: Proscan PLDED3996A led backlight help

TV is alive!!!!!!!!!! Thanks everyone especially to tom66 for point me to the right direction
It was a bad transistor(QS12)

[tom66]

Re: Proscan PLDED3996A led backlight help

Nice one, sorry I did not have time to get back to you, how did you determine that to be at fault?

[boxingfan]

Re: Proscan PLDED3996A led backlight help

i was going from the on/off pin to the other end testing all components and following the beep, and when i checked the QS12 i got O.L where ever i put the proves so i decided to pull it off and replace with one i took from one of the many boards i have, and i got lucky,i paid $30 for it

[tom66]

Re: Proscan PLDED3996A led backlight help

I'm very surprised that any random transistor would work but nice fix!
Do verify that backlight turns on/off OK - for example when switching sources, you do not see noise or errors on the screen which clear shortly after.

[boxingfan]

Re: Proscan PLDED3996A led backlight help

it has been on for about 1 1/2 h, i did an ota scan, tested all hdmi outputs. lights comes on and off normally, i dont see anything wrong(yet) lol, i'm gonna keep the tv on and going through all the menu

[boxingfan]

Re: Proscan PLDED3996A led backlight help

The transistor I got is very similar to the QS11 that is next to the QS12. Do you think the QS12 and the QS11 are different ?