Samsung UE22D5003 - constant restarting

I’ve never ventured much into TV repair, but a friend of mine who works at a tire shop uses this TV at lunch break, to play some games with colleagues. However, it started developing an issue where it suddenly would start “rebooting” by itself.

He asked me if I could take a look at it, and sure enough, he brought it to me.

I started verifying the usual suspects: Some capacitors with elevated ESR were replaced. Voltages were good. No broken MOSFET’s. No failing diodes. No abnormal hotspots. Really a random issue.

I factory reset the screen, and still nothing. From time to time, it does it. It just restarts the panel.

And then while tinkering, I just displayed a white background, and it remained on. For a long time! So I messed with the menus a bit and noticed that the brightness of the panel was constantly changing. In such cases, the screen would start rebooting. So it must be something with the PWM driver.

However, information on these devices’ internal workings is scarce, but I did find a way to disable the PWM… Lo’ and behold: there’s a PWM pin that gives feedback from the mainboard, to the power supply.

Do you see it? Pin 2 - Called EPWM. I just disconnected it, and taped it with some Kapton tape to the wiring loom.

And success! - No more flashing backlight and the TV doesn’t reboot anymore. Technically, we fixed it, by disabling a functionality of the TV. Is that good or bad? It depends. This TV isn’t worth investing much time in, and it’s an “occasional use” device. The fault is probably on the mainboard itself, but as said: not economically viable to spend the money.

Nice little fix on an intermittent fault. Took some time to figure out. Good fun. Happy repairing! - 73 de ON8AD