Samsung UN46EH5300 No Picture

[aquaman8]

Hi,

Problem: No backlight, but flashlight test shows picture.

Same power supply board (BN44-00667A) and CNL802A connector as in this thread (https://www.badcaps.net/forum/showthread.php?t=50896).

CNL802A has pins labelled as follows
D1+ D1+ S1- S2+ N.C. S2- S3+ D1- D1-

Measured + 226 VDC between D1+ and chassis ground both with and without the plug to the LED strings connected.

Based on my web searches I believe that a problem with the LEDs is likely, but I would appreciate confirmation from someone in this group.

I would also like to understand how the LED strips are organized. I know from above-mentioned thread that the backlight consists of 4 strips of 11 LEDs each (6 left and 5 right side per strip), but I am having difficulty figuring out how the LED strips are wired to the CNL802A plug. Are all 4 strips in series? Does pin 1 (D1+) go to the anode of strip 1 (referring to the 4 horizontal strips as 1 to 4 from top to bottom), then to S1- and so on as follows

Pin #1 --- strip 1 ----- Pin #3
Pin #9 --- strip 2 ----- Pin #4
pin #2 --- strip 3 ----- Pin #6
pin #8 --- strip 4 ----- Pin #7

I came came up with this scheme based on the S pin designations on the labels thinking they were possibly current Sensor points for the power supply. I might be totally wrong, but am ready to be educated by anyone who does not mind helping me out!

I have attached a photo of the power supply board (BN44-00667A) as well as a close-up of the CNL802A connector on that board.

Does anyone know of a place where I can get a schematic for this power supply board? I am quite good at finding schematics, but this one seems to be very elusive. Any help would be greatly appreciated. I know I do not need this level of detail to troubleshoot, but I would rally like to understand how the board works and what it does when it does not work!

I was also curious (sorry this is such a long post!!), but though I found a Service Manual for this TV, there is no schematic and no info at all on the power supply!? Is there a separate Service manual for power supplies??

Thanks in advance for any and all help with this. Its a friend's mother-in-law's TV and it is her sole companion!

Mitch

[budm]

Re: Samsung UN46EH5300 No Picture

You have open circuit in the LED string, when it is working, the Voltage should be less than 200V, see the chart printed on the board for the LED voltage when it is load.
Look at the bottom side of the board to see how the LED connector pins are conencted to each other.

http://www.shopjimmy.com/samsung-bn4...led-board.htm#
Pictures provided by shopjimmy.

[aquaman8]

Re: Samsung UN46EH5300 No Picture

Thanks and appreciate the reply.

I did look at the trace side of the connector and saw that the following were connected:

Pin 1 &2 (D1+)
Pin 3&4 (S1- & S+)
Pin 6&7 (S3+ & S2-)
pins 8&9 (D1-)

So I see all strips are in series.

Is a schematic for the BN44-00667A available somewhere?

If I can't find appropriate LED strips, is there a source for individual LED that are good quality? I know there are difficult to remove and replace, but I am experienced with SMT component removal and replacement, so I would be willing to give it a try! Success not guaranteed!! I have heard that there are a lot of questionable replacement LEDs out there and would like to avoid cheap counterfeit LEDs

Thanks again for you help,
Mitch

[aquaman8]

Re: Samsung UN46EH5300 No Picture

I have not cracked it open yet, as wanted to be sure it was a likely LED issue before I risked doing more damage to it!

Based on what I have read regarding this model, I am a little confused as to how the wiring harness which connects the LED strips to the power supply (PS) are wired. Basically, I am wondering if I could check the LEDs for operation without removing the LCD display, by isolating the strips at the connector?

Right now I believe that the the strips connect to the Power Supply as follows:

The connector which plugs into the PS board has the following pinout

Pin Detail
1 D+ pins 1 & 2 are joined on the PS PCB
2 D+
3 S1- pins 3 & 4 are joined on the PS PCB
4 S2+
5 N.C.
6 S2- pins 6 & 7 are joined on the PS PCB
7 S3+
8 D- pins 8 & 9 are joined on the PS PCB
9 D-


So given the above, here is how I imagine the LED strips are wired


LED strip 1 Connector pin 1 to anode, 3 to cathode
Led Strip 2 connector pin 4 to anode, 6 to cathode

LED strips 3 and 4 are connected in series,cathode of strip 3 connected to anode of strip 4

LED strip 3, 4 connector pin 7 to anode of strip 3
pin pin 8,9 to cathode of strip 4

Is this a correct understanding of the wiring? As I said I have tried to combine all the info I have found on the web, but some of it seemed contradictory. Again, my goal is to see if I could test the LED strips separately without having to remove the LCD display. This would give me a quick idea of the extent of LED damage (i.e. strip 1, 2 or 3/4).

Of course a wiring diagram for the strips would be really useful, but I have had no luck finding one. I have looked and begged for a schematic for the BN44-00667A power supply as well, but it seems to be either rare or it does not exist. I would really like to look at one to try to understand how it functions.

Anyway, sorry for the long message and I appreciate your time! Any help/ideas/tips would be really helpful!

Thanks again,

Mitch

[abagnani]

Re: Samsung UN46EH5300 No Picture

Aquaman,

Did you ever get this worked out?

I stumbled upon your post because I have the same issue.

I have backlights that work, but do not get as bright as they should. Perhaps only 1 of the LED strips is bad? Did you figure out a way to test this?

[Sleddriver]

Re: Samsung UN46EH5300 No Picture

Wow...this is indeed an old post. Long before my recent one which is similar. Wish he would have posted that SM. Schematics for these 'newer' SS's are indeed difficult to locate.