Sony Model KD-60X690E no picture

I think an LED problem is more likely. The LED strips are usually powered by a driver circuit on the power supply board. You can check this with a bright flashlight shining on the front of the display at about a 20° angle from parallel to the display. If you can see the picture or the menu with the flashlight beam during the "dark" period, the problem is NOT likely to be the T-Con board.

You can also look at the back of the set with the cover removed - most sets have a number of vent holes in the back plate through which the backlight can be seen when it is on. If these holes go dark when the TV goes black, the backlight is being turned off.

When the screen is lit, take a picture quickly and look for dark spots. Maybe one of the LEDs has a partial short that shuts down the LED power and triggers a retry cycle. If so, after a while it will burn out and then the entire LED strip will be inoperative.

Test the LED strips with a variable power supply to the specified voltage. Test the voltage output to them with a multimeter.

But this is the usual outcome. At least you have a picture.

https://www.fixya.com/support/r29790007-repairing_own_television

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You should be able to replace just the bad LED strips however with as much work as it is to get the set apart and back together I always replace all them as other strips generally fail in time. Did they all light up after you replaced the bad ones before you put it back together? This model set has local dimming so servicing it is a bit more complex, you could have a bad backlight driver but that board seldom gives issues, also you could have main or power board issues as power for the backlight driver comes from the power board or you could have main issues as it's the signal from there that turns on each strip.

Unfortunately Kris the answer I give isn't going to be one you want to hear. I've had the exact thing happen a handful of times on set's I had apart to replace the backlights, I'm not totally sure what happens but I believe your screen (panel) was damaged when it's removed and replaced, could have been from static when handling it, I don't know exactly what happens to it but when it's put back together it does exactly what your set is doing when unhooking one of the ribbon cables going from the timing to panel boards. On one occasion I had a set the same model and series and replaced every board, connector ect and in the set I had the panel out of I didn't get a picture, put everything back in the set I had repaired and it worked again, only thing I didn't change was the panel. One thing you can try is check all the smd capacitors on the panel boards for shorts, if you find one shorted remove it, I've had issues with them being bad on a few sets and make the picture black. Sorry I don't have better news for you

There isn't one, just like there isn't a muffler belt on your car...lol...Backlight inverter boards are used on LCD TV's with CCFL lamps, you have a LED lit set. If you don't have a picture and the backlights aren't on chances are you have bad backlights. On this set it's been somewhat common for the defective lamps to damage the power board, I would order both. Below is a link for the parts, will run about $100 with shipping and your local sales tax. Changing the strips is time consuming, use extreme care removing and handling the panel, watch some vids on you tube before trying to do it.

Faulty LED backlight strips. If only 2 years old, contact Sony for assistance.

This sounds like a backlight issue....... If you shine a torch light into the screen do you see a faint picture? If yes then definitely a backlight issue but it could be the led backlights blown or the T-con board, further tests would be required to determine which.

The backlights are located around the edge of screen inside the tv. Now this model is know to have LED failures. The LED strips are you backlights. The LED strips are powered by the power supply board but due to the fact that this model is know to have LED failures, I would recommend replacement of the LED strips, all of them, first. Samsung BN96 25300A Replacement LED Strips UN32F5000AF UN32F6300AF
This website currently doen't have the parts in stock for your tv however this will help you identify the parts and they even have some tutorials.

If you need further help, reach me via phone at https://www.6ya.com/expert/steven_a67ead41eb5fc62a

Check and replace the back-light LED strip. Contact any service technician. http://electronicshelponline.blogspot.com/

An LED TV is still an LCD TV, just with LED backlighting. That model is an LCD TV. The difference is in the backlight. Both LED and LCD TVs use an LCD screen. LED TVs have LED backlighting of the LCD screen, which saves energy.