Samsung U60J620DAF Power and Backlights blink

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Thanks for the reply. I left my meter at work. The only one I have at home has rechargeable batteries and it might be awhile. I will get back to you.

[nomoresonys]

Re: Samsung U60J620DAF Power and Backlights blink

So with everything unplugged from powerboard, you do have steady 8 volts on standby pin on CNM803?

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Yes, I tested them before and after I installed them prior to putting the panel back together. The only connections I had to make was the LED connector to the PS and the AC.

[nomoresonys]

Re: Samsung U60J620DAF Power and Backlights blink

Wonder if the new strips were faulty before you installed them, did you test them?

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Thanks, bud.

In summation.

-TV On - Backlights flash on and off in sync with the front power light.
-Got new PS - exact same symptoms.
-Got LED tester - Can light all strings from power supply end. Can"t verify they are all lit through the back holes, but each string stays on steady.
-Assuming it was LEDs, obtained 12 new strips from SJ, disassembled panel. -Using tester all original LEDs tested good.
-Figured I had gone this far, I would put in new strips anyway. Installed, all new strips tested OK and I could light both strings from the PS connector.
Assembled panel and connected everything.
-Saw one brief flash of light and powering up over and over did nothing.
-Removing wires from PS connector, top string won't light, but lower string will.

-Swore alot then disassembled panel.
-There are 6 rows of strips. Top 3 compose one string, bottom the other.
- From the power supply end, the top strips do not light, but the lower 3 will.
-Tested each strip individually. Top strip is dead. No Leds light. 2nd strip has 5 good LEDs and the 3rd strip is OK.

What in the world have I done? Right now, I have 2 PS boards, the old strips which seem to be working, 2 dead strips and 3 new strips.

I contemplated about putting the old strips back in, but seems like I am just going in circles. Appreciate some help.

[budm]

Re: Samsung U60J620DAF Power and Backlights blink

107 V is the Forward Voltage of the LED string @30mA of driven current.

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Found a broken display TV identical to mine on Craig's list. Took the PS and put it in mine. Same flashing backlights issue. Bought this little led tester thing which is advertised everywhere. The TV has 2 strings. Using the tester on one string at a time disconnected from the power supply, both strings lit up and stayed on but at a low level as seen through the holes on the back of the display. Both strings had the exact same reading of 107 on the tester. Am not really sure what the 107 DC means. Looking for input before I disassemble the display. Thanks.

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Am trying to make a schematic of the LED Driver section of BN4400775A power supply for this TV. I ran across a 7014X which is addressed on the board as IC9151. I can not find a datasheet for him, but this one keeps popping up in my hunt. OB2268/9. It is a PWM Controller with 8 pins like the 7014X. I don't know if this is just a coincidence or if I have run across something useful. I searched for 7014X on this site, but only found it mentioned on jason123 post about his Samsung, but it wasn't his problem. May still have to get into the LEDs, but figure I might try to learn something along the way.

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Here are some better pictures of the front and back of PS. Am currently trying to read up on LED Driver circuits and will attempt to trace circuit on board.

[budm]

Re: Samsung U60J620DAF Power and Backlights blink

That is fine, just have to look deeper in that LED driver section next.

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

OK, with black on cathode reads a constant 287.8K ohms. Reversing the leads so red is on cathode, starts around 300-400K ohms and just keeps increasing.

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Thanks for the reply. I will do this tonight when I get home and report back.

[budm]

Re: Samsung U60J620DAF Power and Backlights blink

Can you do the diode resistance reading again with it solder in place?

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Thanks jason123 for the diode. It came today. Measured resistance on new diode. Measured 0L one way and 292K ohms the other. Diode test revealed 0L and .497VDC. Assuming this diode to be good, I placed it in the power supply board, connected everything back up and upon plugging in to AC, symptoms are unchanged. Power light and backlights flash repeatedly in unison every second or so.

[jason123]

Re: Samsung U60J620DAF Power and Backlights blink

in the mail today! sorry wasn't able to make to the post office yesterday

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Thanks. Address on the way.

[jason123]

Re: Samsung U60J620DAF Power and Backlights blink

Happy to do it.. pm me your address

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

Thanks Bud, I will get one from somewhere, install and report back.

[budm]

Re: Samsung U60J620DAF Power and Backlights blink

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.

[MEB]

Re: Samsung U60J620DAF Power and Backlights blink

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