Samsung S24A350H Backlight Problem

[Schorsch87]

Hi Guys,

i have a problem with my Samsung Display. The LED-Backlight doesn't work anymore. I can see the picture using a flashlight. At start-up the backlight lights up for a split second. The Mainboard has a connector for the LEDs. The connector has 6 pins. 1,2 named LED1 LED2, 3,4 named V_out and 5,6 named LED3 LED4.

The LED named pins have stable voltage of about 4V. The other ones aren't very stable. It jumps from 13,92V to 36V and then pumps down to 13,92V.

So, please help me.

Regards

[cmia]

Re: Samsung S24A350H Backlight Problem

Pictures of the board please / read the FAQ

[Schorsch87]

Re: Samsung S24A350H Backlight Problem

The small connector leads to the LED backlight. Both pins in the middle have the pumping voltage. The other ones read the stable 4V.

Regards

[Schorsch87]

Re: Samsung S24A350H Backlight Problem

Hey, does anybody know something that would help me?

[Schorsch87]

Re: Samsung S24A350H Backlight Problem

Come on guys :/

[jetadm123]

Re: Samsung S24A350H Backlight Problem

The external power adapter provides a 12vdc output, correct? Odd that you're seeing a 36V spike at V_out. I would try the following: test the input voltage from the power adapter right at the input jack of the motherboard. If you still see the 36V spike, then there could something wrong with the power adapter itself. I believe the LED pins should be driven at 5VDC, but you're reading 4V, which could indicate a possible short or a bad voltage regulator. As a final note, please verify your meter is operating correctly. Measure a 9V battery to verify it's reading voltage correctly. If not, try replacing the meter's battery.

[budm]

Re: Samsung S24A350H Backlight Problem

Please post the P/N of the LED DRIVER IC, it looks like it uses 4 strings of LED.

[Schorsch87]

Re: Samsung S24A350H Backlight Problem

I tested the power supply right at the input jack on the mainboard. The voltage is stable at 14V.

Here's the partnumber: BD9264EFV 149 H36

Regards

[Schorsch87]

Re: Samsung S24A350H Backlight Problem

Another ideas?

[budm]

Re: Samsung S24A350H Backlight Problem

So far I have no luck finding the data sheet for this IC (BD9264EFV) yet.

[JoeyJoe]

Re: Samsung S24A350H Backlight Problem

Is the power adapter supposed to be 14v? What is the rating on the label?

[Schorsch87]

Re: Samsung S24A350H Backlight Problem

Is the power adapter supposed to be 14v? What is the rating on the label?

It's the right voltage. 14V and 2.14A is the rating.

I have no idea what the problem might be. And I don't find an Service Manual with test points or something like that. I don't know the backlight works. If I would know I could test it with an external power supply.

Regards

[jetadm123]

Re: Samsung S24A350H Backlight Problem

One suggestion: around the area of the LED driver that budm circled, try looking for a fuse marked something like FXXX (where XXX is some number). If there is a fuse check it for continuity.

Also, please provide a more focused photo of the circled area where we can actually read the numbers stamped on the board itself.

[ben7]

Re: Samsung S24A350H Backlight Problem

The BD prefix leads me to believe that the LED driver IC is made by Rohm. BUT, I can't find this chip listed on their website
It might have been a custom order chip, maybe you can contact Rohm to see if they made the BD9264. They do have a chip listed on their site as BD9267, which is an LED driver. OR, perhaps the BD9264 is an obsolete part. You'd think they would still have the datasheet for the obsolete part though...

[Schorsch87]

Re: Samsung S24A350H Backlight Problem

Here I have a more focused picture. Can't find any fuse. I thought about a defective cap, maybe a SMD, but I don't own the right testing device. Just a multimeter.

Thanks for the advice ben7.

Regards

[jetadm123]

Re: Samsung S24A350H Backlight Problem

This is a tough one since there's no datasheet for the BD9264. Difficult to know which pin does what. I only thing I can suggest is to check the power mosfet right above the inductor, L101, for a short. The mosfet is stamped 9997GH. Look up the data sheet for a AO9997GH. With power off and your meter set to resistance, place your probes across:

Gate-->Source
Source-->Drain
Drain-->Gate

[Schorsch87]

Re: Samsung S24A350H Backlight Problem

I had already checked the mosfet. This is what I do first. The power mosfet is in a good condition and shows no shortcut.

[flocko]

Re: Samsung S24A350H Backlight Problem

Hi can you check the voltage on the six pin plug again but using the two center pins3/4 as the common as they look to be joined see what do you get pin1 and pin3/4= p2 and p3/4= p5 and p3/4= p6 and p3/4=

[Schorsch87]

Re: Samsung S24A350H Backlight Problem

I do not know what has happened, but the Display is working again. I wanted to measure the voltage over pin1-pin3/4 and after placing the measuring tips the backlight started working?! I'm a little bit confused
Now I have to monitor if it is working on every condition.

Regards

[flocko]

Re: Samsung S24A350H Backlight Problem

It sounds to me as if you could a cold solder connection on the two common pins number 3/4? glad it working for you Regards flocko