Samsung / Hansol BN44-00428b

[budm]

Re: Samsung / Hansol BN44-00428b

It is edge lit LED backlights setup, 4 LED strings total per diagram (from looking at the A and the B version, the component designators are not the same but using the same setup).
I still do not understand by the LED does not even flash on once before going into shutdown, it will have to detect that one or more of the LED strings are not working by trying to fire up the LED, if it detect shorts or open, then it will go into shutdown.
You may have to remove the LED strings and check each LED, you should also check to see if any one of the wires leading to the LED strings are shorted to the chassis.

[kenny1070]

Re: Samsung / Hansol BN44-00428b

" (from looking at the A and the B version, the component designators are not the same but using the same setup) "

That was my assessment as well, which is why I was able to use this solely as a template and simply substitute the designators to match (I little extra work, but sometimes you just have to do).

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" I still do not understand by the LED does not even flash on once before going into shutdown, it will have to detect that one or more of the LED strings are not working by trying to fire up the LED, if it detect shorts or open, then it will go into shutdown. "


And this has been confusing me all along (and still does).
Is it really flashing and I just didn't see it ??? - I don't know.
Now that the panel is dis-assembled and I can clearly see the Leds, I may try it again.
My only other thought would be in the IF1 & IF2 (of the 22 pin conn.) that I have yet been able to decifer. Do they play into the shutdown (protection mode) ?? - If so, how ??


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" You may have to remove the LED strings and check each LED, you should also check to see if any one of the wires leading to the LED strings are shorted to the chassis. "


Can positively say that all the wires are good. I have verified this not only visually, but ohm and induced amp testing (power probe).

I already ordered a replacement Led Bar - but would still like to know the how and why.

I have never actually tested an led before (and don't even know how).
But if you would be willing to teach me, I'd be more than happy to learn - and appreciative.

[budm]

Re: Samsung / Hansol BN44-00428b

You can use three 1.5 batteries connected in series to get about 4.5VDC then put a 220~330 Ohms 1/4W in series with the + lead, Then you can probe each White LED to see if it will light up, the Anode will be connected to the output end of the resistor, the negative will hook up to the Cathode, if you are not sure which is Anode or Cathode, you can just reverse the wire, you cannot damage the LED since it has resistor to limit the current.
I still have to find time to read the training manual, too busy right now.

[budm]

Re: Samsung / Hansol BN44-00428b

"Samsung UN55D6400U" I finally had the time top look through the service and the training manuals, they are nothing like your BN44-00428 board at all.
UN55d7000 uses BN44-00428A per shopjimmy.
What voltage does the chart shows for the LED? 176V?
As you can see, the Cathode return of the LED string is connected to the MOSFET that is turn on by the PWM circuit to set the brightness, if you use small Ohm resistor on the Drain pin (I.E, PIN 7 of CN801A) and ground, the LED for string 1 will come on but you have to make sure that you do have VF1~4 present.

[kenny1070]

Re: Samsung / Hansol BN44-00428b

I saw that on shop jimmy as well.

I do know that this set has never been serviced - since the day it was brand new, so I can't explain why I have this particular board. Wish I had a better answer.

Been over this 1000 times, Can't believe I missed that whole block (wow).

I guess that would have to make this 197v as designated by the key on the top / left corner (marked).

46" - PSLF151B03A = 176v

55" - PSLF171B03A = 197v


So are you thinking that there is just not enough voltage being supplied to the Leds ?

[budm]

Re: Samsung / Hansol BN44-00428b

So you were only gettinG about 125VDC? That is probably not enough the forward bias the LED strings, I see that the filter caps for the VF are rated at 400VDC which is high for 125Vdc supply.
The VF power supply (4) is a booster circuit (two MOSFETs and inductor, IC 9151S)) that boost the VDRV to higher voltage (low current) for supplying the LED strings.
So what dc Voltage do you have at VDRV output? See page 3 of SCH, since VDRV is generated by the same transformer that also generates B13V and other voltages, see what you get on those outputs.

[kenny1070]

Re: Samsung / Hansol BN44-00428b

Won't be able to re-assemble and test that until Sat.

Working 13 + hr. days today and tomorrow.

If you could help me out with exactly where I should be testing - that would be great.

Thanks

[budm]

Re: Samsung / Hansol BN44-00428b

You have to look at page 3 to see the VDRV and the B13 test points, but since the designators of the the REV A board do not match the REV B, you have to do some work to locate the test points.

[kenny1070]

Re: Samsung / Hansol BN44-00428b

Here is what I found in/out of the TM801S.
Had to repost whole PDF annotated (see pg 3).

My DMM registered the A/C input in high voltage (HV).

I had absolutely no other output voltages from the unit - including B13.
Which is a little weird, because I register 13v at the CN801 connector & elsewhere at various jumpers.

Confused.

[budm]

Re: Samsung / Hansol BN44-00428b

OK, it seems to me that the Vdrv is about right at 124VDC (Filter caps are rated at 200VDC), it means that the voltage booster circuits are not working to boost that 124V to 197V.
The IC9151S/9251S are not running. I cannot find the spec sheets for the IC to understand how it works yet. You may want to check the voltage at the VCC pins.

[kenny1070]

Re: Samsung / Hansol BN44-00428b

OK, here's what I am finding :

- Unlike "B" board, the B13 is utilizing Both Mosfets from TM801S
- Vamp (17v) has no Mosfet - direct feed to CN801

Working up a diagram & pictures to explain a little better.

Here's the puzzling part:

- No output voltage from TM801S at B13 or Vamp (all 4 = Ground )
- Backfeed voltage only at all --- terminated at Diodes & Mosfets.
- Found Burn marks on terms 4, 5, 6 of TM801S ( B13 & Vamp output)

Could the lack of supporting voltage be the failure in boost ???

[kenny1070]

Re: Samsung / Hansol BN44-00428b

So it turns out that you were right all along.

This is the wrong board for this machine.

In my earnest to try and track down an actual scheme and possible parts list, I called Samsung (J&J International). I spoke with their tech guys and they insist that there is absolutely no way that this board should have been in this model. Their only hypothesis as to the how, is that it may have been mistaken for the UN55D6400UR model (which does accept it) instead of the 6400UF (which does not). Basically, a clerical error.

So, obviously this board had to have been changed.
Gonna have to talk to my neighbor again (who gave it to me).

So it looks like I'm buying a new board - BN44-00428b.
Don't want to risk moving forward and frying something else.

[mmartell]

Re: Samsung / Hansol BN44-00428b

Hi Kenny did the new board fix your issue ?

[mmartell]

Re: Samsung / Hansol BN44-00428b

...

[asmilie]

Re: Samsung / Hansol BN44-00428b

I recently had the same issue with my UN55D6420 after 2 years and 3 months. The television would intermittently reboot while watching and symptoms progressively got worse over the course of 4 months until the television would not turn on at all. I did unplug the TV for about 2 days and after plugging it back in, it seemed to work for about a day.

After reading multiple forums, I decided to replace the SMPS, which seems to have fixed the problem. There were no visible signs the board failed. If I get some free time, I may try to diagnose what on the SMPS board failed.

[Knackster]

Re: Samsung / Hansol BN44-00428b

Guys,
I'm looking for the same board to replace in my TV but everywhere I look the board is out of stock.

Anyone know of a reputable place that I can get one from?

Thanks,

Chris

[737mechanic]

Re: Samsung / Hansol BN44-00428b

*****Fixed******

I had the same exact problem as the OP and this is what fixed my problem.

I found that the main transformer TM801S had a cold solder if you look at the 3 pictures I posted. The first shows the front of the board with a yellow arrow pointing at the joint that was bad. The 2nd and 3rd show the back of the board with a yellow arrow pointing at the bad joint. I hit it with my soldering iron and problem fixed.

BTW I found this problem because I just happened to see that joint arcing every time the power relay would click.

[stj]

Re: Samsung / Hansol BN44-00428b

some of the other joints are visibly cracked too.
that's why some of us tell people to re-solder transformers sometimes.

[relaxteb]

Re: Samsung / Hansol BN44-00428b

*****Fixed******

I had the same exact problem as the OP and this is what fixed my problem.

I found that the main transformer TM801S had a cold solder if you look at the 3 pictures I posted. The first shows the front of the board with a yellow arrow pointing at the joint that was bad. The 2nd and 3rd show the back of the board with a yellow arrow pointing at the bad joint. I hit it with my soldering iron and problem fixed.

BTW I found this problem because I just happened to see that joint arcing every time the power relay would click.

Seems i had the same problem. Found a cracked solder and resoldered it. Seems like that solved my click issue.

[JOSman]

Re: Samsung / Hansol BN44-00428b

I have the same problem, must try this.

Thanks