Samsung U32EH4003 problem.

[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.

[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.

[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?

[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 !

[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.

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 ?

[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.

[dick_barton]

Re: Samsung U32EH4003 problem.

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

[HellasTechn1]

Re: Samsung U32EH4003 problem.

What you can do is provide focused photo's of the legend on the board. The photo you have provided is not focused.

I will focus on the highlighted spots. It's my camera...

Power supply /LED driver board P/N BN44-??????

BN44-00664A

[budm]

Re: Samsung U32EH4003 problem.

Power supply /LED driver board P/N BN44-??????

[dick_barton]

Re: Samsung U32EH4003 problem.

What you can do is provide focused photo's of the legend on the board. The photo you have provided is not focused.

[budm]

Re: Samsung U32EH4003 problem.

That's right. I removed the blown LED and soldered a new 3V LED. I am not aware of it's current tating though.
Iv'e used the same on an other samsung and worked fine.
They appear to be 3V led's. It has 2 strips of 9 LED's each.

I'll look for the original led stripe though and see...

Iv'e learned something new here today. The constant current supply used for the LED's.

Are all LED backlight TV psu's like this ?

Yes, they use constant current circuit to drive the LED, the more current the brighter it gets..
"It has 2 strips of 9 LED's each." so 18 LED total, that is more likely to be 6V LED, I have seen that before in some SAMSUNG panel, you should verify to old working LED Vf rating.
There is label for the LED output Voltage under load, I cannot read it due to poor quality pictures.

[dskall]

Re: Samsung U32EH4003 problem.

I am working on same model except for F on end. Some led's are bad. Tested one with led tester. It showed 3.7v at around 300ma. My meter goes from 200ma to 20a so resolution not good. Anode is on small pad. Trying to source some led's for it.

[HellasTechn1]

Re: Samsung U32EH4003 problem.

That's right. I removed the blown LED and soldered a new 3V LED. I am not aware of it's current tating though.
Iv'e used the same on an other samsung and worked fine.
They appear to be 3V led's. It has 2 strips of 9 LED's each.

I'll look for the original led stripe though and see...

Iv'e learned something new here today. The constant current supply used for the LED's.

Are all LED backlight TV psu's like this ?

[budm]

Re: Samsung U32EH4003 problem.

So you installed NEW LEDs on to the LED strips, What is the spec of the replacement LEDs?
Some of these 32" SAMSUNG uses 6V LEDs.
Total numbers of LEDs.?

[dskall]

Re: Samsung U32EH4003 problem.

They measured D+ to ground not D-

[HellasTechn1]

Re: Samsung U32EH4003 problem.

Okay that makes sense. On the video though he measures 180V on both D+ and D- to chasis while i get 0V from D- to chassis.

[dick_barton]

Re: Samsung U32EH4003 problem.

The voltage alters because the leds are driven by constant current, let's say 400mA. When there is no current being taken the voltage continues to rise to supply the current until it reaches it's maximum voltage and cannot supply any more voltage.

If it was driving a string of leds let's say at 65V @ 400mA and you added 2 more leds to that string then the voltage required would rise by (2 x 3V) to 71V and still supply 400mA to the leds.

[HellasTechn1]

Re: Samsung U32EH4003 problem.

That's really weird. I have replaced other samsung TV's burned LED's with the same LED i used here and i had no problem at all. How come it gives 140V open circuited.
Why would the Strip work when i apply 27V from my bench PSU ?

Does it make sense to you ?

How the 140V go down to about 57V for the LED's to work ?

P.S. colour temprature does not match but for only 1 led it's no big deal. forward voltage is the same (i think).

[dick_barton]

Re: Samsung U32EH4003 problem.

I can't find any details yet on the panel but I suspect from the shopjimmy video that the problem is with the replacement leds not matching the original.
They are not interchangeable from one lcd set to another but must match maximum current, forward voltage and colour temperature.
The high voltage when the leds are open circuit or connector disconnected appears to be normal as shown in the video.