Chosen Solution
I too have come across this problem for the first time since I bought this Samsung UN55J620. It first turned off or so it seemed, then started a crackling/popping noise in the back near the power cord area. Then I began smelling burnt wire or plastic, I quickly unplugged it. After 30min, I opened it up (removed one back cover) and inspected the power mainboard. Nothing there was burnt up. Although something that resembles a transformer had two of the leads sorta melted. I inspected all the solder points for “Cold-solder” but found none. So I am at a loss. I am considering purchasing the power mainboard for starters. I am just wondering if anyone has truly found both, the problem and solution. Update 02/03/22 I hope this info can shed some light on the condition of the PS or Main/logic boards shape. This is how far I have reached. Attached you will find some corresponding photos. However, I thoroughly inspected the PS with magnifying goggles and a light. I found no “Cold-Solder” joints on either side, no burnt thru marking (other than the darker spots around the diode areas. I should have included a photo of the rear of that board, but I forgot.I do have a multi meter, but I am no Tv repair expert, to be measuring constant resistances and voltages etc. Aside from being a retired A/B work mechanic, I have worked on Cb, Vcrs, Radios, replaced ICs, caps, diodes, resistors etc. I am however, willing to take a plunge here. On photo #2 I drew a Red arrow, this was to ask or say, I assume from what I have seen on a video, that those wires power the LEDs, am I correct? So far, I unplugged that LEDs connector from the PS and tested each lead to see if the LEDs light up, using lite external battery power (four 9v batteries together). Each strip has 14 LEDs, each at 3.0v, = 42v.. I used 36v. I had my son watch the screen for any LED light up, as I applied the voltage to each lead. Unfortunately, most of the LEDs did not light up. A few did, and I believe the top row. So the burnt LEDs was the smell of burnt wire or plastic I was smelling as we heard the crackling. I am assuming perhaps over-voltage may have caused this? In general, When it was all together and I plugged it back in, I would use the remote to turn it on, the Red light blinks 4x and stops, but nothing comes on. The Red light at the inputs panel or Logic main green board on the far left turns on, so does the Blue lights in the middle panel board (T-con).Once again, let me be clear on the “On/Off” issue, the Tv doesn’t turn on, meaning, there’s no picture or a blue screen when On button is pressed. However, when I use the remote and press the power button, the Red Standby light blinks 4 times then stops, this normally means the Tv is turning on. With this, the Red “Optical input light” turns on, so does the Blue Leds on the T-con board. Now, using again the remote, I press power to shut off and Tv shuts off. But, if I try this with the power button on the Tv, it will work as with remote, but when I press Tv button to shut off, it doesn’t work, all the mentioned lights stay on, only I use remote or unplug power cable. Also, I checked for voltage at the connector, which goes out to those LED leads, (see photo), and there was no voltage at those pins. So I assume the power circuit for those LEDs went bad. I also did another test, which I heard indicates if the PS is functioning. With everything connected back and the power cable attached, I pressed the remote power button, and waited for the “pretending” powerup, then I disconnected the cable connector traveling from the logic/main board to the PS ordinarily or supposedly, doing this would cause all the working LEDs to light but it did not. Of course, I already know there’s no power going to the LEDs. The odd thing, or perhaps not, is that I tested for voltage at that black connector and it has 12.65v at all 4 pins, 4.50 on the Stnby pin etc. So I find this weird,- power at this connector, but no power to the LEDs. Also, I took the chance (while system is powered on) and tested those big and small rec/diodes and there was no power on the positive side, but there was on the negative side. Normally current flows one way on the + anode side of the diode towards the cathode side. Unless this means these diodes are shot without showing physical damage.
@jpbravo7 this “something that resembles a transformer had two of the leads sorta melted.” could definitely be an issue. You want to go ahead and post some images of the complete board and of the damaged connections. You could try and find a schematic for the board and see what happened. There must be a reason why this happened and it is unlikely that the failure originated with the “transformer” but most likely with the circuitry to it. Adding images to an existing question
