Samsung U60J620DAF Power and Backlights blink

[MEB]

I have this 60" Samsung that is 18 months old. When plugged in to AC, the red power led on the front of the TV AND the backlights flash in sync with each other once every second or so. This will happen indefinitely until AC is removed. I have unplugged the main board from the Power Supply and symptoms repeat as before. I have enclosed a few pictures to start, but will take more later as it is dark outside. Thank you.

[Andrew F. Ali]

With everything connected see if STD-BY5V is constant or pulsating, also.

[CapLeaker]

do you see any picture during that flashing spell? What I mean is if the mainboard runs and just the backlights flash?

[MEB]

Andrew F. Ali - Expected to see STB-5V by the connector shown in the upper center of the attached photo, but did find this SB:8V on the power supply board. If it is somehow related, I got 3-5 VDC fluctuating wildly. It didn't match the beat of the power led and backlights but maybe my meter isn't fast enough.

Mr. CapLeaker - when plugging in to AC and seeing that flashing spell, I saw nothing that resembled picture. But with LEDs disconnected from PS and plugging in to AC, the power LED behaved normally and by turning on and hitting source on the remote, me and my flaslight were able to see the source menus at the top of the screen. The set powered down by itself shortly thereafter.

[Andrew F. Ali]

SB:8V is the stand by voltage. I do think you have a LED Backlights problem Do you have any experience at all in disassembly of the Panel and removing the fragile glass screen??

[MEB]

Yes, I have done a few, but only up to 46". I guess handling the glass that big and finding a place to put it is probably the hardest part? Any words of wisdom are welcomed.

[Andrew F. Ali]

A 60 incher is a big job. You would have to get a buddy to help you with this one. I use six (6) suction pads/cups. Three (3) at the top and three (3) at the bottom. Using long wooden broom handles, pass them through three (3) of the suction pads/cups handles and secure them with masking tape at the top and do the same again for the three (3) of the suction pads/cups at the bottom. Then from opposite sides lift together and rest it down on a carpeted floor covered with a bed sheet. This works for me. Luckily I don't get much 60 or 70 inchers to repair.

[MEB]

Sounds like a good plan. How big, I guess diameter are these suction cups? What are they normally used for to help me find them?

[Andrew F. Ali]

The ones I have are 4-6" in diameter. They are used for lifting sheets of glass. Try e-bay as that is where I got mine from.
What voltages are you seeing on the Backlight LED + and - pins with the black DMM probe on the chassis GND.

[MEB]

Thanks. I will check there.

[Andrew F. Ali]

What voltages are you seeing on the Backlight LED + and - pins with the black DMM probe on the chassis GND.

[MEB]

Thanks for the reply. I am currently away from the TV but will report back after I get home.

[CapLeaker]

Turn the backlights waaay down and see if it kinds of remedies the problem.

[MEB]

Not exactly sure what I am looking for here, but all I can give you are values with the AC plugged in. With the LEDs disconnected from the PS, the TV will power up with remote but not for very long. So plugging in with the LEDs connected gives D+ =160 VDC. With the LEDs disconnected gives D+ =420 VDC. Both when LEDs are connected and disconnected, D- fluctuates around so much I can't really come up with good readings. Let me know if I am not giving you what you need and I can try again.

[budm]

Lift one leg of the diode D9001C or remove it off the board and then check the RESISTANCE in both directions of that diode, report the resistance reading, make sure that you do not touch the probe tips with your hand because I want to make sure it is not showing your body's resistance.

[Andrew F. Ali]

Originally Posted by MEB

Not exactly sure what I am looking for here, but all I can give you are values with the AC plugged in. With the LEDs disconnected from the PS, the TV will power up with remote but not for very long. So plugging in with the LEDs connected gives D+ =160 VDC. With the LEDs disconnected gives D+ =420 VDC. Both when LEDs are connected and disconnected, D- fluctuates around so much I can't really come up with good readings. Let me know if I am not giving you what you need and I can try again.

Yes. So far you are doing an excellent job.

[MEB]

Thanks budm, always a pleasure.

Black lead on Cathode - 235.2K ohms
Black on Anode - 0 ohms

Appears to be SF28G. Thanks.

[budm]

Originally Posted by MEB

Thanks budm, always a pleasure.

Black lead on Cathode - 235.2K ohms
Black on Anode - 0 ohms

Appears to be SF28G. Thanks.

OK, that reading does not make sense if it show 0 Ohms in one of the reading and 235K in another. Are you testing by putting the probes on each end of the diode?
I think you may have the same diode failure like in this thread with the same diode P/N.
https://www.badcaps.net/forum/showth...t=72153&page=2

[MEB]

Yes, I repeated the test several times. Digi-Key and Mouser both have the SF28G or would you recommend trying to upgrade? Any suggestions?

[budm]

I would get a couple of them for either place then, and when you mount it on the board keep the legs long so the body will be 1/4 ~ 1/2 '' above the board to help cooling the diode.
https://www.badcaps.net/forum/showth...t=72153&page=2 the diode did fix the problem on that OP board.
I ask Jason to see if he can ship the extra one to you.