Sony KD-75X750H no backlights

[x_orange90_x]

I just removed the back cover to test the backlights because when I first plug it in it will flash once and then start dark but I can see the image. I got 131v on string 1 and 167v on string 2. Usually when I get a bad set the meter reads 300v and they won't light up. When testing, each set lights up inside the tv. When I plug in the power and check the leads with my multimeter both strings are only about 3v.

Does this difference in voltage between the strings indicate that the lesser has bad LEDs? Or is it normal that they are not the same voltage? I've read some about this tv and no backlights. Since people say they replaced them and it still did not work, hunting at a power supply issue.

[nomoresonys]

With the flash and the difference in your readings, it's probably a bad backlight or two or three...

[howardc64]

Google led strips shows each string is 4 bars x 13 LEDs. 4x13x2.7v/LED=140V assuming both strings have same # LEDs.

Whenever I’ve had LED readings different from the calculated string voltage. Failure has been LEDs.

I’m guessing your PSU shut off backlights when detecting it was out of range.

You could try the following for more definitive confirmation but probably really hard. Need more hands or secure led tester to light string hands free.

with led tester connected to 1 string for backlight. Run a white screen test on YouTube. Can see failed LEDs easily. An external streaming stick already running white screen test might make it easier.

[x_orange90_x]

Google led strips shows each string is 4 bars x 13 LEDs. 4x13x2.7v/LED=140V assuming both strings have same # LEDs.

Whenever I’ve had LED readings different from the calculated string voltage. Failure has been LEDs.

I’m guessing your PSU shut off backlights when detecting it was out of range.

You could try the following for more definitive confirmation but probably really hard. Need more hands or secure led tester to light string hands free.

with led tester connected to 1 string for backlight. Run a white screen test on YouTube. Can see failed LEDs easily. An external streaming stick already running white screen test might make it easier.

I may try this. The most difficult part isn't really securing the tester leads into the plug, it's maneuvering this thing. I had my wife help me lay it down on the table and she was struggling to get it up high enough. Diagnostics would be much easier if they didn't require you to remove the feet in order to get the back cover off.. That is purely unnecessary.

I'm pretty confident that it's bad LEDs causing this. The voltage difference would suggest that an entire strip is out, likely due to a single bad LED 🙄

[howardc64]

I may try this. The most difficult part isn't really securing the tester leads into the plug, it's maneuvering this thing. I had my wife help me lay it down on the table and she was struggling to get it up high enough. Diagnostics would be much easier if they didn't require you to remove the feet in order to get the back cover off.. That is purely unnecessary.

I'm pretty confident that it's bad LEDs causing this. The voltage difference would suggest that an entire strip is out, likely due to a single bad LED 🙄

I usually put tv on bed /carpet upside down (often the fragile buffer boards / flex is exposed during diagnostics ) then not too hard to hold it vertically or lean against the wall. makes navigating menu a little difficult

[nomoresonys]

For the big ones it would be nice to have one of those big slanted stands for working on them, very costly but have seen some diy ones made of wood that look very useful. Specially when you need to see the display and such while trying to work on those monsters.