PHILIPS 75PUS7805/12 BLACK SCREEN

[bohaboha]

Hi all this set power on and the ambient lamps lite but the screen is black and no sound i tried Samsung way to test backlight but it did not work i did also try to power of and hold power for some times nothing happened
on power supply big capacitor :394v on tcon the 12v and 3,3v even on Mainboard

[ShaunRutherford]

Check the cables from the mainboard to the T-Con and from the T-Con to the panel carefully, making sure they are not loose or broken.

[bohaboha]

ok i ll do a sherlocks investigation on them thank you

[William1967]

The "Samsung way" to test the backlight does not work on a Philips. So I guess there is no backlight available? 99,9% the backlight is broken.

[bohaboha]

do there is any way to be Shure it is a backlight before opening this big beast quite heavy

[nomoresonys]

Backlight tester, they are not perfect but very handy for testing backlights, 15 dollars and up at amazon and the usual places.

[nomoresonys]

This type is good, more versatile, you can adjust the voltage and current for more accurate testing. It helps to be able to provide more than the typical 30 mA of a lot of the testers which is helpful but not near enough for accurate testing. Specially when working with the bigger screen tvs: https://www.youtube.com/watch?v=7UqAqxJdIDI

[nomoresonys]

This example has the better specs and would be more versatile: https://www.amazon.com/SID-LED-Multi.../dp/B07MT87G2P

[nomoresonys]

This is the lowest price one I see on amazon with the decent specs, I wish I would have paid the bit extra when I bought one: https://www.amazon.com/Backlight-Mul...=CIHQzb8_tjNJf

[bohaboha]

This is the lowest price one I see on amazon with the decent specs, I wish I would have paid the bit extra when I bought one: https://www.amazon.com/Backlight-Mul...=CIHQzb8_tjNJf

Hi i have the usual one and as you say they are not not perfect ill try it but not Shure about it

[EazyBone]

Did you take a strong flashlight to the screen after you turned it on? Some tvs you'll see a picture.

Also what do you mean the ambient light comes on..? Like the led indicator on the TV?

But definitely if you fix tvs gonna need LED tester as they say. I got the same one Sony talking about, it's never once failed me.

[bohaboha]

both are on the red led indicator and the light on the back cover around the edge . i did try with my phone flashlight but it is not strong i ll try to find a better one .for the backlight tester i have this simple one and To be honest I don't know how to test this backlight connector see the picture and please tell me how to do it correctly thank you

[bohaboha]

Did you take a strong flashlight to the screen after you turned it on? Some tvs you'll see a picture.

Also what do you mean the ambient light comes on..? Like the led indicator on the TV?

But definitely if you fix tvs gonna need LED tester as they say. I got the same one Sony talking about, it's never once failed me.

both are on the red led indicator and the light on the back cover around the edge . i did try with my phone flashlight but it is not strong i ll try to find a better one .for the backlight tester i have this simple one and To be honest I don't know how to test this backlight connector see the picture and please tell me how to do it correctly thank you

[EazyBone]

Stick black probe where shown in the picture. Each hole is a ground to a specific red. Stick red probe on red line.

Make sure power supply is disconnected from clip before testing them.

Usually LED tester is safe to accidentally touch probes together also.

It will read like 80v (example number) when you have them connected properly. And will show nothing when you have a shorted line or you aren't putting it in the correct red/black pair. So move them around. Experiment.

But when the voltage goes to 80 or so you'll see light in the back of tv.

Obviously don't do this with AC plugged in

[bohaboha]

Stick black probe where shown in the picture. Each hole is a ground to a specific red. Stick red probe on red line.

Make sure power supply is disconnected from clip before testing them.

Usually LED tester is safe to accidentally touch probes together also.

It will read like 80v (example number) when you have them connected properly. And will show nothing when you have a shorted line or you aren't putting it in the correct red/black pair. So move them around. Experiment.

But when the voltage goes to 80 or so you'll see light in the back of tv.

Obviously don't do this with AC plugged in

'Hi the test black probe on ground (chassis) red probe on red wire =45V step up to 51.5V all of them and there is not a single hole to se the light even with this result it should not light the backlight then i believe i have to get to the backlight it is a big screen and quite heavy set

[lotas]

The backlight is never connected to the common ground! Power + is constantly supplied to the backlight connector, and - (negative) is disconnected, adjustable, controlled by the backlight drivers via mosfets. Here is your connection diagram...

[bohaboha]

The backlight is never connected to the common ground! Power + is constantly supplied to the backlight connector, and - (negative) is disconnected, adjustable, controlled by the backlight drivers via mosfets. Here is your connection diagram...

Hi lotas and thank you so my test procedure was wrong then how should i test it black probe to C8622NC and the red probe to VLED+ if I have understood correctly?

[lotas]

Yes, red is a common + for all backlight strips, and black is -, for each channel separately (that is, two different -).

[EazyBone]

Haha yea forgot to post the picture.