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Samsung TV Continuously Turns on and off (power cycle)

Hi,

I have a 50” Samsung TV model number UN50TU8000FXZA, I dont know much history about the TV. There is a date of 2019 on the power supply board. I have done the following troubleshooting so far:

Symptoms:

When plugging in the TV, the Samsung logo comes on the screen, and within 1-2 seconds the logo becomes partially garbled, and additional 1-2 seconds the tv turns off and then turns back on, starting the cycle again. When plugging in the tv, i can see the leds on the back go through 3 stages of brightness and on the last (when they are the brightest) the logo comes on. I reseated all internal cables with no change in symptoms.

Steps done so far:

  1. I checked all capacitors on the power supply board, no bulging tops.
  2. I left the TV plugged in for about 5 minutes and the cpu on the main board registered 125 degrees F. Seems hot for a resetting/non functioning cpu, but i dont know what to expect.
  3. Disconnected the cable to the main board. Plugged in the TV, the LEDs come on and I measure the following voltages in order at the LED connector on the power supply: 209V, 171V, 171V, 96V.
  4. On the power supply board, the voltages for the main board connection are as follows: 1-G, 2-G, 3-13V, 4-3.3V, 5-13V, 6-3.3V, 7-13V, 8-0-1.4V, 9-13V, 10-0V, 11-G, 12-0-1.6V. Pins 8 and 12 fluctuate between 0 and 1.4/1.6 volts, it spends about 3 seconds at 0 volts, then changes to 1.4/6 and drops back to 0.

Does anybody know if these voltages are in spec? the pins at 13V are correct, there is a label on the board, but the remining pins are descriptions, not voltages. I’m wondering if pin 6 should be 5v? Anybody have any other steps I can try? I can’t really find much in the way of schematics online, so i’m kind of stuck as to where to go next. I really hate to throw money at parts, i’d rather have make an educated guess. My initial thought from what i can tell is the power supply seems ok, it is puzzling i dont see 5V anywhere, which is what drives a lot of electronic boards. I suspect the main board but hoping there is a way to further diagnose.

Rispondi a questa domanda Anch'io ho questo problema

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Update: I unplugged the ribbon cable from the mainboard to the LCD panel, plugged it in and it seems like it booted! Nothing is on the screen, but the LEDs changed brightness a few times, then stayed on constant and i got some kind of boot up sound out of the speakers.

da

2nd update. The main ribbon cable plugs into a long and skinny circuit board that has a ribbon cable connecting it to another long and skinny board. These two boards have additional ribbon cables that come off and (i think go to the lcd panel?). When i disconnect the ribbon cable between the two circuit boards the tv boots. ugh.. i dont think there is much else to do? bad panel?

da

3rd and last update. I was able to replace the buffer boards, a real pia, i do not recommend. It did not fix the issue, i must have a bad/shorted lcd panel. TV went into the trash.

da

Mine did did the same thing , power kept turning on and off , I can just imagine how many more of these model # are garbage , mine went into garbage also , next I will buy Sony , goodbye Samsung😡

da

Has anyone looked at the back of the ribbon cable connecting the main board to the bottom of the screen. I have noticed mine is blackened where there is a hole in the metal back panel. It is also blackened lower near the connection. I’m wondering if the heat over time could have corroded the tiny copper cables in that ribbon cable. I ordered a new ribbon cable to test if that resolves the issue. If it does, i’ll just have to find a way to shield from the heat w/out retaining the heat on the back panel.

da

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7 Risposte

Here’s what Samsung says to do:

https://www.support.com/how-to/how-to-fi...

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I did this 5 times, with no change, thanks tho.

da

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A power fluctuation may be the reason for the error. Also don’t forget to take your TV adapter(if present) for a physical examination and see if the capacitor on the power unit is working.

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did you replace the power control board? seems like the drop in voltage is stemming from there

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Just happened to me. I was going to do what dudes do, take it apart and start replacing things, but instead I just let the stupid thing turn off and on all night long. 10hrs later it's working like normal.

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Heres what worked for me. Let television keep doing power cycle, kept pressing settings button on remote. Eventually got the settings menu and went to support option and picked software update. Television installed update and now working fine.

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I opened up my tv and found that my cable to the power button had a wire exposed. I cut and stripped wire and soldered them together. This fixed the issue with the power cycle for me. I have ordered a new cable because I only want this to be a temporary fix.

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Same problem here. Good picture for about 2 minutes at initial plug in, then off and on with no picture and a 2 flash code.Unit picked up at the side of the road. mfg data april 2021.There are no ttl circuits the 3.3 volts runs the chips and processor. Used freeze spray ,no luck. I recently placed it outside at -10 deg c and will see what happens tommorow morning. I,ve salvaged and repaired 8 ea 50 to 65 in tvs which mostly had a few bad leds. All donated to charity.

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Guy in Desert sarà eternamente grato.
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