Samsung un32eh5000f No backlight.

[Nitro468]

Samsung un32eh5000f No backlight Can see picture with flashlight.

I'm new to working on LED's fixed plenty of other stuff already.


Powers going to LED
CNL 802

Pin 1 149.5 VDC
Pin 2 128.2 VDC
Pin 3 Not used
Pin 4 128.2 VDC
Pin 5 0.343 VDC

What should I expect ?
Any way to test the LED strips ?

Thank You
Chris

[budm]

Re: Samsung un32eh5000f No backlight.

You have open LED sting that is connected between pin 4 and pin 5.
Samsung BN44-00665A (L32GF_DSM) Power Supply / LED Board

[Nitro468]

Re: Samsung un32eh5000f No backlight.

I was thinking open circuit with the readings.. Is there anyway to bench test them ?

What voltage should I expect, I couldn't find a schematic or service manual for it...

[budm]

Re: Samsung un32eh5000f No backlight.

Right now you are getting 149.5V on pin 1 which is the Anode of the whole LED string, pin 5 is the Cathode return of the whole LED string.
If you look at the Voltage chart as printed on the board, you will see LED Voltage of around 90V with load.
You will have to open up the LCD panel assembly to get to the LED strips to test each one to see which one has open circuit. You will have to test each LED on the failed strip to find out which one/ones is/are bad.
There are more than one version of the LCD panels used in this model, so you must verify what you have.
http://www.shopjimmy.com/catalogsear...ng+un32eh5000f
Fail LEDs are very common failure, when you get it fix make sure you turn down the backlights level.

[jbfr_54]

Re: Samsung un32eh5000f No backlight.

Testing and fixing the LEDs is quite easy and inexpensive but watch carefully when you dissassemble and reassemble the panel. Due to the fact the panel has no screws but only pop-up tabs on the plastic surrounding the LCD, it is is difficult to open and necessitates to put force on the frame for dissassembling. Worse is reassembling as each of the frame tabs must be pushed toward LCD to be locked, again it is necesary to apply important force and the tabs click strongly agin the panel. So, last week, one fixed screen broke by itself without any mechnical strenght or move of the set two days after fixing. I imagine the lcd was broken on the edge for a few 1/10 inchbefore being broken on several inches on the high left hanside corner, probably due to temperature changes. Too bad they switched from screwed metallic panel frames to plastic clipsed system !

[thoma]

Re: Samsung un32eh5000f No backlight.

http://forum.iwenzo.de/grundig-servi...e--t61847.html

see also here

[Nitro468]

Re: Samsung un32eh5000f No backlight.

Thanks for the explanation on the voltages, I had the feeling it was the strips... Disassembly was a bit of a pain, thank god it wasn't a bigger panel... There might be firmware update to address the LED life issue, but I will turn them down....

[ossroy]

Re: Samsung un32eh5000f No backlight.

My Samsung UN32EH5000F is having a very similar problem. Rather than NO backlight, I have a very dim picture. I don't need to use a flashlight to see the picture, but can just see it in the ambient light of my bedroom, which is far from well lit. It does occasionally flicker, getting ever so slightly brighter or dimmer, but it is way too dim to be of any use. Adjusting the backlight setting has no effect. So I replaced the T-CON board after reading that it's a common problem with the backlight and it was only 12 bucks with shipping. Symptom did not change. So now I'm thinking the PS board and not the LED strips since there is some bit of brightness. If it was a bad LED, my understanding is the screen would be totally black. Does this sound correct? Thanks for any thoughts you may have.

Roy

[nomoresonys]

Re: Samsung un32eh5000f No backlight.

@ Roy, Test connector from mainboard to powerboard on powerboard side, sholud be a little legend/map of expected voltages, test with tv plugged in but off then hit power, report both conditions here, give pin number, pin description and condition on and off, demonstration in signature below.

[neilc6]

Re: Samsung un32eh5000f No backlight.

You most likely need full LED strip replacement. Samsungs do not have protection to shut offf the LED supply so backlights will continue to burn out until the screen is dim. You can force the backlight on by unplugging the cable between the main and power supply board. Fairly simple to remove the panel on a 32 inch TV but you still need to be careful. Lower the backlight level on all inputs and all smart apps to around 60 to 70 after replacement.

[ossroy]

Re: Samsung un32eh5000f No backlight.

Thanks guys; I'll open her back up this evening when I get home from work and check things out.

-Roy

[budm]

Re: Samsung un32eh5000f No backlight.

check out this thread: https://www.badcaps.net/forum/showth...ung+ue32eh5000
Also perform main board disconnect to see what will happen to backlights.

[ossroy]

Re: Samsung un32eh5000f No backlight.

With TV plugged in, but OFF:

Pins 1-13 (odd) No voltage

I didn't measure 2-14 because pins were inaccessible.

With TV ON:

Pin Label Voltage

1 B13 13 VDC
3 B13 13 VDC
5 Vamp 13 VDC
7 Vamp 13 VDC
9 GND 0 V
11 B5V 5.2 VDC
13 B5V 5.2 VDC

Pin Label Voltage

2 PWM 1 VDC
4 B13 13 VDC
6 BLU 4.8 VDC
8 GND 0 V
10 GND 0 V
12 A5V 5.2 VDC
14 PS 3.5 VDC


I had to unscrew and flip the board over to measure the even pins, taking great care not to short the pins with the probe tip.

-Roy

[nomoresonys]

Re: Samsung un32eh5000f No backlight.

Did you unhook cable from mainboard to powerboard, see if backlights come on and stay on? as suggested in post #10.

[ossroy]

Re: Samsung un32eh5000f No backlight.

I unhooked mainboard from power board while TV was powered down, and TV would not turn on in that condition. Should I have unhooked them while TV was powered on?

[nomoresonys]

Re: Samsung un32eh5000f No backlight.

No, you did it right.

[budm]

Re: Samsung un32eh5000f No backlight.

With TV plugged in, but OFF:

Pins 1-13 (odd) No voltage

I didn't measure 2-14 because pins were inaccessible.

With TV ON:

Pin Label Voltage

1 B13 13 VDC
3 B13 13 VDC
5 Vamp 13 VDC
7 Vamp 13 VDC
9 GND 0 V
11 B5V 5.2 VDC
13 B5V 5.2 VDC

Pin Label Voltage

2 PWM 1 VDC
4 B13 13 VDC
6 BLU 4.8 VDC
8 GND 0 V
10 GND 0 V
12 A5V 5.2 VDC
14 PS 3.5 VDC


I had to unscrew and flip the board over to measure the even pins, taking great care not to short the pins with the probe tip.

-Roy

You can use skinny probe tip to access the Even number pin via the wire entrance of the connector.

What does not make any sense to me is that you reported " Rather than NO backlight, I have a very dim picture" but you also report "Pins 1-13 (odd) No voltage". If B13V is not working then the T-CON cannot be working either.

[budm]

Re: Samsung un32eh5000f No backlight.

I unhooked mainboard from power board while TV was powered down, and TV would not turn on in that condition. Should I have unhooked them while TV was powered on?

When you unhook the cable between the main board and the power supply board then plug the TV into the outlet, that will put the power supply and backlights driver circuits into self-test mode (it the board has pull-up resistors), so if the power supply, LED driver circuits, and the LED strings are OK then the backlights should come on and stay on as long as the TV is plugged in.
At this point you need to report the Voltage on the power supply connector that goes to the main board and also at the LED connector (LED connector in place).

BTW: Line Voltage: 170V P-P @ 16.6ms. That should be 120 V RMS X 2.828 = 339.36 V P-P.

[ossroy]

Re: Samsung un32eh5000f No backlight.

You can use skinny probe tip to access the Even number pin via the wire entrance of the connector.

What does not make any sense to me is that you reported " Rather than NO backlight, I have a very dim picture" but you also report "Pins 1-13 (odd) No voltage". If B13V is not working then the T-CON cannot be working either.

I didn't have any skinny probe tips, so I just ordered a set from Amazon this morning.

As far as the No Voltage on pins 1-13 (odd), that was when the TV was plugged in but turned off. As shown above, I did have 13V on pins 1, 3, 5 and 7 when the TV was turned on. Or should have I have seen voltage there with the TV turned off as well?


-Roy

[ossroy]

Re: Samsung un32eh5000f No backlight.

When you unhook the cable between the main board and the power supply board then plug the TV into the outlet, that will put the power supply and backlights driver circuits into self-test mode (it the board has pull-up resistors), so if the power supply, LED driver circuits, and the LED strings are OK then the backlights should come on and stay on as long as the TV is plugged in.
At this point you need to report the Voltage on the power supply connector that goes to the main board and also at the LED connector (LED connector in place).

I will have to try again tonight. I had other obligations last night and never got a chance to look at the TV, and now I'm second guessing myself on what all happened on Tuesday.

BTW: Line Voltage: 170V P-P @ 16.6ms. That should be 120 V RMS X 2.828 = 339.36 V P-P.

Now that's embarrassing! I used the formula for Peak and then wrote P-P.