Sony KDL-75W850C 6 red blinks - where to measure LED voltage

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Bruce White @bmwhitetx

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Postato: 12 ago 2018

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Sony KDL-75W850C 6 red blinks - where to measure LED voltage

I am troubleshooting a Sony KDL-75W850C per the service manual. 6 red blinks indicates either bad power board or LD panel. I have checked power board and I have good 3.3v STBY, 12V, and BL_ON. . It says I need to measure the LED output voltages. I assume I measure them between OUT+ and OUT- on the board. All the other points are measured to Ground. The reason I ask is I get a brief pulse of 132V between OUT+ and OUT- then it collapses to 0. If I measure between OUT+ and Ground I get varying voltages from 0 to 200V ( I assume a cap is charging discharging).

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My friend, I’m struggling to have access to the backlight panel.. do you have a service manual or can you give me some tip where I canget there? I’m in a point now where the TV is 80% disassembles, but I don’t know how to proceed to take the LED panel appart from the LCD screen. Thansk a lot . Eduardo

21 giu 2020 da djedumolina

It has been a while. It seems like once I removed all the screws I was able to get the back off to see the circuit boards. From there I don't remember the process to get to the panel but it seems the bezel was difficult to seperate. Sorry, I can't be much more help. FYI, two years later, another strip went out. We decided to scrap it at that point.

21 giu 2020 da Bruce White

Having the same problem, looking for information on how to replace the strips. If anyone can help or point me in the direction that would be great.

10 mag 2022 da Nelson justiss

@nelsonjustiss it'll depend on your TV's model number. To replace the strips is fundamentally the same on all of this LCD TV's. Take a look at something like this guide It'll be pretty much the same way. The issue is that the larger the TV the easier it is to crack the LCD screen. Amazingly enough they are pretty flimsy and love to flex. To find a backlight array (strip) it is best to get the LCD assembly number of the sticker affixed to the back of the display. Do an online search and see what you find. Of course, if you have the number already or if you are not entirely sure, let us know what it is and we can most certainly try to assist you with that.

10 mag 2022 da oldturkey03

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Abrsvc @abrsvc

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Postato: 12 ago 2018

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There is an LED or two that are out on one or more of the strips. You will need to test the strips and/or the LEDs to locate the one(s) that don’t work. A single shorted LED can cause this. Please note that there are protection circuits that shut down the LED supply to prevent further damage. This is why you see the short pulse of 132V.

Dan

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5 Commenti:

Thanks for the quick reply. What is the best way to test without opening the panel which I assume is a lot of work? Can I disconnect the OUT +/- wires and validate the power supply voltages? Or disconnect the T-con board? The service manual is at a dead end - just says replace LD panel.

12 ago 2018 da Bruce White

There are LED strip testers out there that can be used to verify this, but its not worth it for one set. I have successfully replaced individual LEDs too. But... You need to know which one and these are surface mounted LEDs as well. There is really no easy way to get much further with this other than removing individual strips to see which one is bad. The LEDs are connected in series. Each one fires up using 3.3V (or close to it) Doing the math, you likely have 4 strips of 10 LEDs per strip. I found 2 listings for one strip each for your model on Ebay for $25 a strip. This seems a bit high, but there were only 2 listings. That is probably what the market will bear.

Talk to a local shop to see if they will either replace the strip or replace the LED if you can locate it.

Post your location. Maybe someone here is close enough to help.

12 ago 2018 da Abrsvc

Ok thanks, I'll look at getting to the LEDs. This is for my church in northern Dallas-Fort Worth

12 ago 2018 da Bruce White

As a followup, I was able to remove the screen to get to the LED strips. I also bought a LED tester on eBay. Very handy device. It quickly I showed I had one LED out on a 10-LED strip. Bought a replacement strip off eBay and it works great.

8 nov 2018 da Bruce White

Hi Bruce,

Can you post some photos of the tools and led replacements?

21 gen 2019 da Dara SOK

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My friend, I’m struggling to have access to the backlight panel.. do you have a service manual or can you give me some tip where I canget there? I’m in a point now where the TV is 80% disassembles, but I don’t know how to proceed to take the LED panel appart from the LCD screen. Thansk a lot . Eduardo — djedumolina
It has been a while. It seems like once I removed all the screws I was able to get the back off to see the circuit boards. From there I don't remember the process to get to the panel but it seems the bezel was difficult to seperate. Sorry, I can't be much more help. FYI, two years later, another strip went out. We decided to scrap it at that point. — Bruce White
Having the same problem, looking for information on how to replace the strips. If anyone can help or point me in the direction that would be great. — Nelson justiss
@nelsonjustiss it'll depend on your TV's model number. To replace the strips is fundamentally the same on all of this LCD TV's. Take a look at something like this guide It'll be pretty much the same way. The issue is that the larger the TV the easier it is to crack the LCD screen. Amazingly enough they are pretty flimsy and love to flex. To find a backlight array (strip) it is best to get the LCD assembly number of the sticker affixed to the back of the display. Do an online search and see what you find. Of course, if you have the number already or if you are not entirely sure, let us know what it is and we can most certainly try to assist you with that. — oldturkey03
Thanks for the quick reply. What is the best way to test without opening the panel which I assume is a lot of work? Can I disconnect the OUT +/- wires and validate the power supply voltages? Or disconnect the T-con board? The service manual is at a dead end - just says replace LD panel. — Bruce White
There are LED strip testers out there that can be used to verify this, but its not worth it for one set. I have successfully replaced individual LEDs too. But... You need to know which one and these are surface mounted LEDs as well. There is really no easy way to get much further with this other than removing individual strips to see which one is bad. The LEDs are connected in series. Each one fires up using 3.3V (or close to it) Doing the math, you likely have 4 strips of 10 LEDs per strip. I found 2 listings for one strip each for your model on Ebay for $25 a strip. This seems a bit high, but there were only 2 listings. That is probably what the market will bear.

Talk to a local shop to see if they will either replace the strip or replace the LED if you can locate it.

Post your location. Maybe someone here is close enough to help. — Abrsvc
Ok thanks, I'll look at getting to the LEDs. This is for my church in northern Dallas-Fort Worth — Bruce White
As a followup, I was able to remove the screen to get to the LED strips. I also bought a LED tester on eBay. Very handy device. It quickly I showed I had one LED out on a 10-LED strip. Bought a replacement strip off eBay and it works great. — Bruce White
Hi Bruce,

Can you post some photos of the tools and led replacements? — Dara SOK

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Sony KDL-75W850C 6 red blinks - where to measure LED voltage

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