Samsung 50" Plasma HPT5044 No Picture

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Trying to figure out where to probe.

I was looking at VR5500 on the service manual. The one on my board seems to be pointed at the opposite direction than the manual. Is this correct or should I change it to the correct postion stated in the manual?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

I highlighted on the image where to probe -- are you doing it without buffers? Sometimes a pin/hook is marked YOUT.

For now you don't need to worry about Yfr as you will be able to use the scope to adjust it.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Which picture? And yes I'm doing it without the buffers installed

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

I posted here.
https://www.badcaps.net/forum/showpo...8&postcount=77

However, since you do not want buffers connected, see this image.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

So heres what I'm getting,

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

So you are at 2V/div with 10X probe, meaning 20V/div.

You should be seeing close to 200Vp-p across most of the waveform (the SUSTAIN portion) but are only seeing about 60Vp-p.

This probably won't blow up the buffers (it's not shorted) but I also don't expect it to work.

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Try to set up scope so you see suggested pic on page 51. Same panel.
http://www.tgohome.com/ServiceManual...&Search=Submit

You can get a decent trigger in 60 Hz countries, like the US, by setting the SOURCE control to "LINE" in the HORIZONTAL section, then set timebase to 10ms/div and V/div to 50V. It will roll the trace slightly but is usually fine. Centre trace in middle such that with no connection the line is in the middle. Also, if you bought it from far away (~100mi or more), you need to adjust the trace rotation control to compensate for the change in Earth's magnetic field. Make sure VAR is in the CAL'd position on all controls (it should click when in the right position.) COUPLING for trigger should be AC for and channel must be DC.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Oh, I had the VAR set on the other side. (Tested a 3 Volt battery and didn't get the right settings for it to show on the scope)

I set it at 5V/div with a 10x probe and now I'm getting this, its about 200V peak to peak? So its working correctly?


On page 51, it says its for a 42" panel? I'm not finding the same components on my board.

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Hmm, looks better. Everything major appears to be there. Try getting a closer shot on 2ms/div. It's a while since I've done this... need more practice... not enough time.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Here it is on 2ms/div

This is the first time I've used a scope, still trying to figure out how each of these settings work .


What do you think you would you see, if lets say that cap that I'm measuring the scope across was bad? Just wondering.

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Tweak the focus control until the image is clearer. Dropping the intensity control can help on older scopes.
It looks good though.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Great! Heres after tweaking it a bit.

What would it look like if it were bad? Would it have spikes or dips in the waves where it doesn't reach or pass 200v p-p?

Okay, I want to check Yset and Yfr (VR5200 and VR5500), I noticed next to the adjustment points on the board theres always a cap. Is that where I should always place the probe to measure the waveforms?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Incorrect Yfr/Yrr just causes a poor picture (maldischarge.) I usually do not bother adjusting them with a scope because I just adjust it by looking at the image.

I see everything I am expecting. Can you zoom into the first subframe, near the first horizontal division? Drop the timebase to 200 or 500µs/div.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

I should be getting the buffers in the mail today, lets hope this works!

So heres zooming in. I had trouble trying to hold off it, I messed with the trigger level and hold off a bit but heres the best I got.

at 50us/div x10
http://www.youtube.com/watch?v=QVtiNTKu8GA
http://www.youtube.com/watch?v=jCPiW93Y_q0

at 20us/div x10
http://www.youtube.com/watch?v=ltCpjBKx3V8

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

It's kind of hard to see anything there because the trigger is rolling. Try using the trigger to latch on the Yfr/Yrr ramps?

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Where do I probe for the Yfr/Yrr ramps?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

The main outputs have Yrr/Yfr superimposed -- they peak at Vs+Vrr, or about 350~400V.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

I think I got it, I had the triggering coupling source set on channel 2 when I was probing at channel 1.

The trigger stopped rolling and heres what I got on 50 us and 20 us with the hold off set on minimum.

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Hmm, it looks good. I normally use my digital scope for this. I can single-shot capture it and zoom right in to the waveform to see each pulse.

[ghiotom]

Re: Samsung 50" Plasma HPT5044 No Picture

I don't know if having the buffers removed makes a difference, but here's a working 50" Samsung panel image. Your image looks more like the abnormal image on pg 54 referring to the Vsch voltage. It should be around -55V and is produced on the Ysus board. Again, it could be because the buffers are disconnected, but that voltage appears to be absent. Disregard those arrows on my image, they are pointing at the Vsetup peaks and were put there for a different thread.