Samsung 50" Plasma HPT5044 No Picture

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

I guess I'll just have to wait for my buffers to come in and see how everything goes.

That photo of that abnormal image on the screen on page 54, I did get something that looked exactly like that, but it was pink when I replaced the mosfet on the ysus and tried to power on the TV with just the Ysus and only the lower buffer board on. (Refer to post #44) I don't know if it means anything.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Okay just got my buffers and installed them. TV turns on now but, gets a white screen, then a loud screech, and then a horrible picture. Heres a video of what I'm talking about...

http://www.youtube.com/watch?v=7OLtRNIWnWg

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

That's most likely bad Yrr/Yfr settings. Try turning them to the default settings. Picture should look OK with some maldischarge. Adjust from there. Also, check Vs and Va voltages -- your Va looks too high causing misfiring vertical lines (be very careful not to damage the panel COFs by leaving Va too high.)

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

I noticed that theres a loud screech sound and then loud buzzing coming from the biggest transformer on the PSU.

Its gradually starts out soft and progressively gets louder, and at the same time the picture seems to get whiter and whiter. (sounds like something is about to blow... but I turn it off before more time)

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

That's basically because the panel is trying to pull more power than the PSU wants to allow or is designed for. When the Yfr/Yrr is set wrong it causes the panel to become excessively conductive with all pixels white. Which for a 50" is more than 600W. Normally the control board limits the brightness to put it at a more sane 400W. (If you test a plasma panel with a solid white you'll discover as you increase the brightness the level will top out around 70%, even though it could make 100% bright on individual pixels when the rest of the panel is not as bright. It is just limiting the average picture level.) I bet Vs will drop out slightly during this.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

How do I lower the Va? Is is clockwise or counterclockwise?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Just adjust it very slowly and watch it with a meter. 1V won't kill a panel. 79V will. (I just blew up my pet 50" plasma I keep for experiments. Turned Va to full one way (79V, sticker says 55V) and one of the COF chips smoked!! Luckily, it already had a bad 2" bar on the panel, so it was toast anyway.)

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Ok just checked my Va, it wasn't too bad, about 0.3V off. I'm checking Vs now and its at 176V! But on the panel stick it says Vs: 206V. Is this right? how did it drop that low? Or am I probing the wrong spot?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

As I said, panel is drawing way too much current, so Vs is dropping (hence PSU noise too.) You need to tackle Yrr/Yfr first. You could also measure Vs with X-main disconnected. You should still get a dim image, which will put the PSU under light load.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

I'm measuring Ve on the X-board and it is also low.

How do I know when adjusting Yrr/Yfr when its at the correct spot?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

You want to adjust it to the default specification.

Default configurations are shown on page "EN 65".

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Alright so I set Yrr/Yfr back to defaults, checked Vscan and adjusted to -190 as in the sticker. Va, Vs, Ve is all also correct, but now I'm getting a constant buzzing/crackling noise from the PSU and the picture is still distorted.

I'm seeing that adjusting Yrr and Vscan effects the picture in some way, but when I'm adjusting Yfr, there seems to be no change coming from it at all. What does it do?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Yfr and Yrr should adjust those ramps you see at the beginning of the sustain waveform. Can you see those change at all?

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Well, I've been messing around with the Yfr and Yrr (just adjusting it left and right until I get a good decent picture) but no luck..
I did remember when testing my Ysus with my old upper buffer (without the IC) I did get some random half top picture on with a loud screech also..

I did use buy the buffer boards LJ41-03882A + LJ41-03883A (not specifically not for my panel), as did dsynder from post #41.

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

It is possible the Yrr/Yfr are in protection. Do you see a lit green LED near the connector going to the control board? This indicates the Yrr/Yfr are limited.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

I can clearly see the ramps changing when adjusting Yrr, but only barely a small change when adjusting Yfr from min to max.

Heres what I measured with my scope at 1ms, 50us, and 20us (at default Yrr/Yfr).

The only time I can get a decent picture is when I adjust Vscan to its lowest (about -173V) While Yrr/Yfr are at default settings, as well as Ve,Vs,Va being correct.

Heres a video of what it looks like:
http://www.youtube.com/watch?v=HfKmBSbVqo4


Heres a video of what it looks like when I set Vscan to -190 (as in the panel sticker):
http://www.youtube.com/watch?v=-Hklpl3k5dI


Vs seems to drop out and down when I set Vscan to the correct value?

Also notice how when I turn on the TV the screen is messed up, as well as when I shut it off. (This also occurs when I am switching the input source, and while TV is suppose to be "black" while it sets to the new selected input.)

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

I do see a green LED light on the board under the main board. No LEDs lit on the Ysus though.

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

LED in question is on y-main, not control board.

There are several fuses on y-main. F4005 or F5005 I think is the Yrr/Yfr fuse and may be the problem.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

I can't seem to find the fuses on the Ymain.. What type of fuse is it? pico, glass, or smd?

Did you see my videos on post #116?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Saw your videos... looks a lot like typical maldischarge though the split in the screen makes me consider Va but you checked that.

Fuse should be pico type, like a resistor.