Samsung U32EH4003 problem.

[HellasTechn1]

Re: Samsung U32EH4003 problem.

There is label for the LED output Voltage under load, I cannot read it due to poor quality pictures.

Where exactly on the board ?

Why when i apply 3V to each individual led it lits at max brightness ? If they where 6V led's then they would not be able to lit at all with 3V applied on them.
It is not only that i have tried 27Volts on each led strip bit also i tried all LED's individually with 3V from my bench psu.

[HellasTechn1]

Re: Samsung U32EH4003 problem.

Thanks for those. Photo 2 says your led string driving voltage is 65V @ 450mA so the leds are 3V leds.

That makes sense. So are the 180V i get normal ? could it be droping to 60V under load ?

note that in serries all LED's must draw equal ammount of current right ?

[dick_barton]

Re: Samsung U32EH4003 problem.

The voltage adjusts itself to supply the fixed current (450mA) as set up by the constant current circuit in the Led Driver IC.
So voltage is variable but current is fixed.

[HellasTechn1]

Re: Samsung U32EH4003 problem.

OK i undertand. Thank you all for your Useful advices and comment's. They are always welcomed.
I will have to stand by for some new LED's. If i get it right i will all let you know !

[budm]

Re: Samsung U32EH4003 problem.

450mA is quite high so the replacement LED should be rated higher than that, since they are using only 18 LEDs to light up 32" screen it is using lots of current more than usual.
But again, it looks like they are cutting down the cost of building the TV.
BTW, what is the Voltage rating of the cap CM807? 250V?

[te71se]

Re: Samsung U32EH4003 problem.

hi all sorry to bump up an old post but I came across this using my google-fu powers.

I have a Canadian market UN32EH4003FXZC with BN44-00664A power supply board and DF320AGH-R1 made in China panel that I trash picked from our recycling room. It powers up makes sound and I can see video by shining my phone flashlight through the screen. I thought ok easy it's just some bad LED backlights but when I tested the output voltages of the power supply I was getting results that seemed to differ from others.

The CNL802 connector reads:

1: D+
2: S-
3: NC
4: S+
5: D-

On pins 1 & 5 (D+ & D-) with or without the LEDs connected I get 170V, and on pins 2 & 4 (S- & S+) I get 0V.

If I measure across chassis ground I get the following:

Pin 1 D+ 172ish V
Pin 2 S- 155ish V
Pin 3 NC nothing (obviously)
Pin 4 S+ 150ish V
Pin 5 D- 0V

Do these readings seem normal?

There is a slight brown discoloured portion of the power supply board around diode D9801C which I guess is a little concerning.

Is there an easy way to test if this power supply is bad for sure? I don't have a LED tester etc though I imagine if the power supply has been putting 170V across LEDs expecting 65V then I probably have some burnt out LEDs too.

[neilc6]

Re: Samsung U32EH4003 problem.

You probably have a lot of bad LEDs. Here's a pic of a UN40H. The diode could be shorted but easy to test with a multimeter. You can also test each LED individually with the multimeter in diode mode. Fairly easy to work on a 32 in TV though it's not worth much. An open LED will cause the circuit to be at the max rated voltage printed on the silkscreen for the board.