Samsung U60J620DAF Power and Backlights blink

[budm]

Re: Samsung U60J620DAF Power and Backlights blink

Pin 1 - UD - +13V
Pin 3 - PWM-BLU - +13V
Pin 5 - PS_ON - +13V
Pin 7 - +13V
Pin 9 - GND = 0 volts

These were taken with the black lead on pin 10 GND.
PS board is only attached to AC.

You must have counted the connector wrong that is why those reading are wrong, no way the control signals can be 13V, please recheck your connector pins.

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Thanks. I will report back after I get home tonight.

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Yes, I did.

Pin 2 - UD = 2.31 V
Pin 4 - PWM_BLU = 3.28 V
Pin 6 = 3.88 V

Pins 1,3,5 and 7 = 12.77 V

Also center leg of DM851C = 12.7 V

Hope this is better.

[jason123]

Re: Samsung U60J620DAF Power and Backlights blink

Hi MEB, any update on this? I have a 40" that is acting the same - flashing backlight. Thanks

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

https://www.youtube.com/watch?v=1kwPFr1VXOo

jason123 Not really. I tried another PS board and it did the same thing. Now I have led issues. The above link is a short video I found, but gives no fix or suggestions.

[vinceroger69]

Re: Samsung U60J620DAF Power and Backlights blink

im sure i saw a video on youtube yesterday regarding samsung flashing back lights they removed the pwm wire from the connector and all was fine i know this isnt a fix as cant alter backlight but did stop the flashing i will see if i can find the video again

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

I have done a complete 360 since starting this. Started out with flashing LEDS and am back to flashing LEDS. If it was the power supply, replacing it with another had the same exact results. Some new strips failed on initial power up, but putting some of the originals back in and all testing good, the LEDS all light with either power supply but flash just the same. The main board is disconnected so it can only be the PSs are both bad and have failed in exactly the same way? I am confused.

[nomoresonys]

Re: Samsung U60J620DAF Power and Backlights blink

Check all the solder joints with a magnifying glass.

[nomoresonys]

Re: Samsung U60J620DAF Power and Backlights blink

With all boards connected and tv unplugged, check those little brown capacitors on tcon board for shorts, meter on diode mode, probe on each end of capacitor.

[budm]

Re: Samsung U60J620DAF Power and Backlights blink

So based on your post 34 & 36 when you test the LED strips outside the panel and powered by the power supply board; they light up OK without flashing ? correct?

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Sorry to be confusing. I tested both strings with little led tester with the power supply to LED connector disconnected from the power board. I could light both strings up that way. When powering LEDs from either one of the 2 Power Supply boards I have, LEDs (both strings) always flash. This is with the LED connector connected to the PS board and the main board disconnected from the Power Supply board.

So, with the PS board connected to the LEDs, whether the main is connected or not, always gives flashing LEDs.

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

OK. I checked all the solder joints on the PS board and saw nothing alarming. It was kind of hard to see with the silicone looking stuff they dumped over the back of the board. I did touch up the 2 connectors though they looked fine. Put the board back in and still have the flashing LEDs.

Then I removed the T-Con board so I could get the heatsink off to get to the capacitors underneath and reconnected it back up. I had to get a microscope to see anything, but I tested every capacitor on the board as instructed and none of them were shorted or visually damaged. I put new heat sink grease on the heatsink and re-installed everything. LEDs are still flashing.

Since the LEDs flash whether or not the main and thus the T-Con board are disconnected or not, doesn't the problem have to be the power supply, the LED wires/strips or failed LEDs ? I sometimes get an idea stuck in my head, so if I am missing something, please tell me. Thanks for all the help.

[budm]

Re: Samsung U60J620DAF Power and Backlights blink

When you perform self test for the power supply/LED driver/LED's by disconnecting the cable between Power supply and the main board, so T-CON or any other boards have nothing to do with self test mode.
So far I have no luck finding fast-track for this model.
Too bad you cannot do the test of the LED strips connected to the power supply board outside the panel to see what you are seeing, using LED tester at low current to test the LED strips is not 100% reliable due to only 30mA of drive current instead of 200 ~ 300mA of real drive current.
When I test the new LED strips, I drive them with the power supply board in self test mode with the LCD panel not in place for 15 minutes to make sure the new LED strips will hold up.

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Thanks, bud. The LEDs have all been lighting in the panel connected to the power supply but continue flashing. I removed the power supply again and removed all the electrolytics. They all tested fine. I ordered new ones to replace all of them just to eliminate them being a possibility. With the power supply back in and powering it up unconnected to anything else but the LEDs, a noise came from the panel, and using the LED tester, I determined the top string of LEDs wouldn't light. This is the second time I have lost the top string. I will take the panel apart again to see what happened.

My wife has issued an ultimatum. I have less than 2 weeks to fix this or I have to buy a new TV before the Super Bowl. I have to fix this one regardless of the outcome of that but am nearly out of ideas.

I ordered another set of strips from SJ and they will probably be here Wednesday. I will test them outside the panel as you suggested this time. Before I do, I want to have a fairly good feeling about the power supply. Can I test the following voltages without burning something up with nothing but AC connected to the board, and what should I expect to see. D+ to D-, D+ to chassis and D- to chassis. I think I should also check the actual wires from the power supply to the LEDs. Also is there any advantage to placing a voltmeter in the circuit to monitor current. I doubt I might be fast enough to pull the plug before damage would occur but was just wondering. This little adventure is getting quite costly but I can't stop now. Thanks for your help.

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Aha, seems like the first new set of strips I bought had problems. I put 3 of the good originals and 3 of the good new ones in there and it is working. As budm eluded to, I think even though the bad strips tested fine under low current with the little led tester, when the PS board was used, they failed under high current.
I think the original problem of the LEDs flashing on and off, must have been some protection circuit on the PS board that shut down and started over and over in a vicious loop. Is that possible?

So I didn't need the 2nd new set of strips I just received, but I am going to put them in there anyway. I don't want to have to do this again any time soon. Thanks to all who helped.

[nomoresonys]

Re: Samsung U60J620DAF Power and Backlights blink

Nice job, seems like it's the backlights 99 percent when you have flashing issues.

[nomoresonys]

Re: Samsung U60J620DAF Power and Backlights blink

Aha, seems like the first new set of strips I bought had problems. I put 3 of the good originals and 3 of the good new ones in there and it is working. As budm eluded to, I think even though the bad strips tested fine under low current with the little led tester, when the PS board was used, they failed under high current.
I think the original problem of the LEDs flashing on and off, must have been some protection circuit on the PS board that shut down and started over and over in a vicious loop. Is that possible?

So I didn’t need the 2nd new set of strips I just received, but I am going to put them in there anyway. I don’t want to have to do this again any time soon. Thanks to all who helped.

Ah, suspected this in post #35. Even shopjimmy sends out faulty parts on occasion BUT they stand behind their parts and will try to make it right.

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Thanks, I learned some things and will know better what to look for next time.