Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

OK. So, quick question.

I checked the voltages at the other M+ pins and got no readings. The only pin I get a reading from is the M1+ pin. I tried it both just plugged in and with the Power Button pressed. If the lights are in series, shouldn't I get power to the other M+ pins on the board?

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

There is no just M+ pin, you have M1+ M1-, M2+, M2-, and on and on as explained.
So what do you have on M1+, M1-, M2 +, M2 -, etc.?
I.E.
M1 + = xx V
M1 - = xx V
M2 + = xx V
M2 - = xx V
......
.....
.....
....

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Oh. I was keeping the Ground on the chassis, like checking the M1+ and followed on to the M2+, M3+.

I just checked it both ways. I kept the Neg Lead grounded on the chassis and checked pins 1, 3, 6, 9,and 11. I only got a reading on Pin 1(M1+)

I did get M1+ reading when I touched the other M- leads. Same readings as before, Fluctuating power between about 285-320v.

I then checked each Pair M1+/M1-, M2+/M2-, etc down to M5's noting Pins 5 and 8 were not wired. Again, the only pin that read any power was Pin M1+.

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Voltage redings are ref to chassis GND.
M1+ (Anode) is the receiving pin of the whole LED string, it is fed by the Voltage from the Boost converter circuit, M1- is the Cathode of the M1 string, so if M1- shows 0 Volt then you have open circuit in the M1 string.

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Oh. So, I haven't looked at it that way.

Should I expect to get a Negative voltage off the M1- lead when referenced off GND?

If I get 300v on M1+, am I looking for -300v on M1-?

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

If M+1 string has open circuit then you will not see Voltage at M1-, just think of it as open wire so you will not see the Voltage.
You have Voltage goes into point A but nothing will come out at point B if circuit has open path.

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

OK. Thanks. I'll open the chassis tomorrow and start looking at the LED stings to see if I can trace down the short.

Since I'm not getting any feedback from M1-, should I expect to find the short along the M1 line? I really haven't played with LEDs very much.

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

You will look for OPEN circuit, you will inspect the wire from M1+ all the way to the strip and then check the connector, if it uses to connect the LED strips together, and then check each LED, etc., this is where LED tester comes in handy for quick test.
https://www.shopjimmy.com/sid-gj2c-l...ght-tester.htm
These may be the same backlights strips as used in your panel.
https://www.shopjimmy.com/samsung-bn...-10-strips.htm

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

That's something I don't have.

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

That's something I don't have.

Actually, I may. I have A Power Probe mater kit that might have what I need. I bought it a couple of years ago to work on a car I no longer have and it's been sitting on the shelf all that time. I'll look through it and see what I can find.

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Yeah, no, never mind. It only works for 12-24v systems.

I just amazon'd a tester. I'll have it in a few days.

Gotta love Amazon. Pay for 1 day shipping and it says it'll arrive in 5 days........

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

I think I figured out the problem. No tester needed. It's strip #1.

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Well test Data show M1 strip has open circuit, so there you go, it is confirmed, that is wht M1- shows no Voltage.
Tester is a second choice to confirm the DATA without taking the panel apart to verify if it has open circuit or not.
I would replace all the strips at this points, it looks like many many LED's were over heated due to being driven at full or above the current rating, so when it is fixed you need to turn down the backlights to may be 50% to extend the life of the LED's.

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Thanks. Will Do.
I think we kept the brightness up because the TVs always seem a little dark in our brightly lit room. Even with curtains, we have quite a lot of naturallight throughout our house and it tends to wash outourTVs when we watch during the day.
It seems that Samsung TV don't last very well, this is the second one we bought and this one barely lasted 3 years from manufacture date. Our previous unit was a Plasma that's probably got bad Capacitors on the board. We'd had it, maybe 3 years before it went bad and then finally found a board to replace but after about 2 more years, it went out again.
Samsung might make some really great phones, but their TVs are crap.

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

LED backlights failure are common on TV's using LED backlights.

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

I'll remember that for next time. I just automatically assumed it was a board from my experience with my Samsung Plasma TV that's still sitting in a corner waiting to be fixed. It was fixed once before with a board replacement. Lasted nearly 2 years and did the same thing again, only now those boards aren't available anymore. I've read that it's probably capacitor issues on them, I just haven't torn into it yet to start looking.

[Andrew F. Ali]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

LED backlights failure are common on TV's using LED backlights.

+1k. I would recommend changing out all the strips and turning down the 'Backlight Level' (not the Brightness Level) after replacement to 65-70%. This way the LEDs will last longer as they would not be working at maximum. Each input may have to be adjusted separately as each input may have different picture adjustment.

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

OK. Is that something I do from the screen in the menu? Or, is it something I tweak on the board? I don't recall seeing a Backlight setting in the menu. But, I don't think I ever looked for one either. Once I get everything put back together, I'll post back. I'm waiting on the lights to come in so I can replace them.

What are your thoughts on using double sided tape to mount them with? Do these things get hot enough to melt the plastic tape? I wouldn't want to do it and create a mess that might cause other problems.

[budm]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

The tape will keep the strips to stay down flat which also help dissipating the heat to the chassis, I will not leave out the tape.

[JohnMcD348]

Re: Samsung UN55H6203AF Suddenly Lost Picture, Now Sound

Ok. Thanks. I'll double side tape the strips down when I install the new ones. At the factory, they were only held down with the little plastic pins on each end and there's 1 long strip os strapping tape running top to bottom.

The other way should be better. Like you say, itll be a better heat sink.