Philips 50PUS7363/12 Backlight but no picture

[groomit]

Hi,
I'm having trouble with above mentioned TV. Bought it defect.
Picture was heavily compressed around the horizontal axis. Fiddeled and tried different things (mask clock lines, swap T-Con). But no difference.
Then I identified a heating capacitor on the left hand Signal-PCB (?) below the display. Replaced it by hand soldering. Checked for shorts afterwards. But now the screen stays black.

I can see backlight, but screen stays black.
What I've tried:
- Disconnect right side cable from T-Con -> same (backlight but no pic)
- Disconnect left side cable from T-Con -> I can see vertical stripes (spanning from top to bottom) near the center of the screen. First one white about 5 cm wide. Then two red'ish stripes. Finally the right half of the screen turns white.
- Tried a different T-Con -> Same behavior
- checked Caps on the left LCD-Connect-PCB for shorts (Small PCB below the screen which distributes the signal to the panel)

Not sure the behavior of the right side is healthy. But definitely the left side seems to have some issues.

Any hints on how to proceed?

[lotas]

Yes, I mixed up the number, remove these D004 from both sides, install resistors and that’s it.

[lotas]

- checked Caps on the left LCD-Connect-PCB for shorts (Small PCB below the screen which distributes the signal to the panel)

Take a high-quality photo of these planks.

[groomit]

Take a high-quality photo of these planks.

Sure. Not sure what is important to see. I can do more and closer pictures if needed.

Took a picture of the whole PCB left and right (looking from the back). And there are two closer ones each showing one half of the suspect side.

[lotas]

Here is this section, close-up and also the second plank.

[groomit]

Here is this section, close-up and also the second plank.

Thanks for taking the time. Here the requested pictures. The diode packs read 4267H. Not sure how to measure them correctly. Found some Infos on the forum and will try to follow.

[lotas]

Check the resistance on these 4 pins of each assembly relative to ground and the resistors (one resistor is not original and is installed incorrectly, it should be 101 (100 Ohm), but yours is 100 (10 Ohm)

[groomit]

I measured all 4 diode packs to ground. All come out open line or in the mega-ohms. Except for 1-2 lines which measure around 4-5k on both pcbs.
Good spot on R075 - this is really bad (o.l.). It should be 100 ohm, right?
Regarding R086 - you found my "work". Now that I see it again (1.5 years after initial try) I'm not quite sure I replaced the small cap nearby or the resistor. Doesn't make sense to replace a warm resistor.
You're sure about the value (100 ohms)? My reference was the other PCB which I considered mirrored. There is a 10 ohm resistor installed.

[lotas]

Well, you can see from the photo that R075 is 101 (101 = 100 Ohm), R068 should be the same. Mostly the assemblies that burn here are D004.

[groomit]

Well, you can see from the photo that R075 is 101 (101 = 100 Ohm), R068 should be the same. Mostly the assemblies that burn here are D004.

Thank you for the explanation. I see you do have practical experience with this TV/PCB - glad you found my request :-).
Just to be sure: By R068 - do you mean my replaced resistor R086? Do you think by adding the wrong value I fried something?
I will have a more detailed look on D004 and report back

[lotas]

Yes, I mixed up the number, remove these D004 from both sides, install resistors and that’s it.

[groomit]

Will do.Is it save to use hot air? Not sure how to attack D004 otherwise.
I'm concerned about the glued ribbon nearby

[lotas]

Yes, be careful, do not damage this tape, the air flow should be low, you can stick foil on the tape and direct the flow of hot air against this tape, the board is thin, the components can be easily removed, you don’t need to overheat, you can drop flux on them and heat them up with a regular soldering iron from above and move to the side...

[groomit]

First intermediate update: by just replacing R075 and R086 I made two observations:
- Plugging both PCBs into T-Con resulted in black screen as before
- Plugging the left one only resulted in holy smoke from R075.

I assuume this is related to the old and defective D004 parts on both PCBs?
Will proceed with removing the D004s and the again defective R075.
Is it possible to test the tv with these D004 removed?

[lotas]

Is it possible to test the tv with these D004 removed?

Yes you can, I never put them back and it works for years...

[groomit]

@lotas: You Are. Genius.
Thank you soo much for your responsive and helpful attitude.
I almost scrapped the TV and you helped me fix it with parts worth cents!