Samsung UN32EH5000FXZA, No Backlight

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

200v

[tom66]

Re: Samsung UN32EH5000FXZA, No Backlight

Could just be the over voltage threshold is set there... doesn't mean the LEDs will operate like that continuously.

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

It does seem to fluctuate from 175V to around 185V and back to 175V without settling down.

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

I have a couple more concerns about the LED strips. There is a connector on both ends of each strip. In my past experience with LED TVs, whenever there was a connector on both ends of the string, there was a jumper to another string. This is not the case here. The connectors at the other end are just open. Any thoughts?

Also, can I buy standard ultra bright white LEDs and solder the leads to the pads for test purposes?

[budm]

Re: Samsung UN32EH5000FXZA, No Backlight

I was going to ask you about that since I only see the cable so on one side only.
Are the + and - markings on both end of the strips?
The way the 4-pin connector on the power supply board are setup, the LED strips look to be connected in parallel so it needs only 2 pair of wires.
No one worked on this TV before, right?

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

I was going to ask you about that since I only see the cable so on one side only.
Are the + and - markings on both end of the strips?

Yes, there are markings on both ends. I'm away from the strips right now, but I believe they are flipped from one end to the other.

The way the 4-pin connector on the power supply board are setup, the LED strips look to be connected in parallel so it needs only 2 pair of wires.
No one worked on this TV before, right?

I wondered the same thing myself. I don't see any evidence that would suggest it.

[budm]

Re: Samsung UN32EH5000FXZA, No Backlight

I never seen 32" LED backlights with just two strips with LED driver out put that puts out more than 150V, usually <100V, 42" larger is >100V.
Something does lot look right, unless there are limiting resistor on the strip that we are not seeing.
Can you also please verify that the two strips are connected in parallel?

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

The two positive pins on that connector are connected as are the two negative pins.

[budm]

Re: Samsung UN32EH5000FXZA, No Backlight

So the two strips are connected in parallel, and each strip has 12 LEDs.
I see on the right side of your picture has two tapes attached to the chassis, what were they taping down? since there are no wires shown in the picture.
I can see that the tapes on the left side is for taping down the wires.
https://www.badcaps.net/forum/attach...5&d=1423004264

This is UN32EH405, as you can see, it uses 4 strips of LEDs.
http://s807.photobucket.com/user/bud...?sort=3&page=1
I thinks some one has been inside this panel before you, no way two strips can light up the panel evenly.
BTW, the label on my board and on your board indicate VLED of 147V, 260mA.

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

The tape was holding down the ends of the LED strips. Unlike any other panel I've ever torn into, these strips aren't stuck to the panel with double sided tape, they are attached with plastic clips stuck through holes in the panel. There are only as many clips as there are holes. The strips in my picture have been detached from the panel. I don't believe there is room for two more strips when it is assembled correctly. The white reflective sheet only has 24 holes in it for the LEDs as well. The white sheet would cover any additional strips.

[budm]

Re: Samsung UN32EH5000FXZA, No Backlight

Hmm, interesting.

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

Interesting indeed.

[tom66]

Re: Samsung UN32EH5000FXZA, No Backlight

It could be that each LED is a two chip module with two LEDs in series, perhaps?

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

It could be that each LED is a two chip module with two LEDs in series, perhaps?

Would I be able to tell when the LED barely glowed? I wondered that too, but I could clearly see two or three LEDs inside each module in the pictures I've seen. I've misplaced my 40X loop though, so I can't say for certain.

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

Any other ideas? I suppose I could attempt to get one good string from the two and see if I can buy the other. Though the PSU output worries me.

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

I found the fast track guide. Thanks again for the service manuals Tom. Page three has a mistake though. The picture shows CNL802 pins 1 through 5 labeled D1+, D1+, N.C., D1-, and D1-. The legend under the picture is reversed. Pins 1 and 2 are labeled D1- and pins 4 and 5 are labeled D1+. With that said, on page 4, it looks like D1+ should measure a constant 110V. I measured again and I'm seeing a steady fluctuation from roughly 172V to roughly 185V. It also says D1- should measure 1.3V-32.8V depending on what Backlight Dim is set to. The higher Backlight Dim measures, the lower D1- should measure. Backlight Dim on my board measure about 2V, right in the middle of the range. D1- both fluctuate from a few millivolts to roughly 3V.

I suspect this power board is faulty and that is what blew the LEDs.

At connector CNL802, there are four wires. Pins 1 and 2 (D1+) are grey and black respectively. They run to one LED strip. Pins 4 and 5 (D1-) are also grey and black and run to the other LED strip. How can this be? Even if the PSU was working correctly, one LED strip would read 110V with respect to ground at both pins on that connector. The other would read 1.3V-32.8V with respect to ground at both pins on that connector. My gut is telling me that there is supposed to be a second harness jumping the two LED strips together.

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

Are you guys as stumped as I am?

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

Looks like I'm on my own with this one. I'll report back once I get it working.

[johnboy1313]

Re: Samsung UN32EH5000FXZA, No Backlight

Power supply and LED strips. I bought a set with a broken screen off ebay for 15 bucks.

[CapLeaker]

Re: Samsung UN32EH5000FXZA, No Backlight

so did you try the old power supply? Just for shits and giggles...