Samsung 50" Plasma HPT5044 No Picture

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

Ok got that. As you can see in my waveform captured above when set at 5v/div it seems to "clip" at +-200v. Using the offset reveals nothing more.

This is an Iwatsu SS-5711 100mhz 4channel scope. Are some scopes designed to not go beyond what the controls are set at or do I have a configuration issue ? I have set the controls as suggested earlier in the thread.

I will lower the V/div so I can use the offset but don't imagine that will produce the form over 200v

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

It's hard to be sure, what's the highest voltage DC supply you have available?

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

There's a few thousand volts in the box out front of my house

Can't I just probe the main filter cap of the PS in this tv, should be about 380vdc, right ?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Nope - that's mains referenced, you'll blow up your ground lead or scope trying to measure that!

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

Oops! Don't want to do that. Is there some household device that puts out that kind of voltage ? I am drawing a blank...

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

If you have something low voltage, say 40V, and a 1X probe, you can test your scope that way...

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

Excellent insight. I think I only have 2 10x probes, they both terminate in little metal boxes. Is a 1x probe the same without the box ?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

I have never seen a probe terminate into a little metal box...

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

Like so... the box has the bnc male connector built into it.

[Agent24]

Re: Samsung 50" Plasma HPT5044 No Picture

That box probably has the adjustment capacitor in it, probably just older and bigger than most.

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

There IS an adjustment pot on the one side. So in this case is a 1x probe physically different from a 10x probe other than that little box ? I ask because I have another probe that doesn't terminate in the box but not in a bnc connector either.

[Agent24]

Re: Samsung 50" Plasma HPT5044 No Picture

Check this out: https://www.youtube.com/watch?v=SX4HGNWBe5M

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

Very good vid, Agent, I think I will watch more videos from that him.

I checked my probes hoping one of them had a switch to go between 1x/10x but nope. There is only a small push button that says "Gnd Ref" for ground reference I suppose.

Perhaps I'll get a 1x probe for this scope, wouldn't hurt to have one.

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

I had another YSUS here and repaired the shorted condition (MOSFETS under lower heatsink) and when installed in the set the conditions and voltage readings are the same.

That's two identical YSUS looking identical when installed.

Can a problem on the XSUS or Control board "appear" on the YSUS ? Is it safe to install the Buffers or where else can I probe ?

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

Hey tom here's a pic of my xmain could you point out where to attach scope probes to check its waveform ? Thabks

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

Since both YMAINS appeared identical (and non-shorted) in circuit I went ahead and installed the buffers one at a time.

With upper buffer alone there was no green light on the YMAIN but the buffer ic's look like they need some work as there were many black or white scan lines.

When I installed the lower buffer as well I didn't manage to get a look at the screen as almost right away the YMAIN protection/fault led came on so I pulled the plug. Both buffers still register NO shorts.

Since the buffers on these sets seem to run in series from upper down to lower could the upper buffer having so many no connects and possible output-pin shorts cause a cascade effect to the lower buffer which would throw the YMAIN into protection ?

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

This is what it looks like when you do a piss poor job on the top two ic's on the upper buffer board. Much better job on the bottom two.

Soon after the pic was taken there was a "snap!" and the top ic was blown. Strange artifacts on the upper half of the screen I hope will be cured by a better soldering job.

But of course that has to wait because my swing-arm magnifier has broken and the magnifier head just dangles by the cord. Lovely.

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

You can hook your probe on the right hand side of the blue caps on the X-main, near the orange ribbons; looking at the image though, you do not have an X-main problem, just an issue with buffer IC soldering or loose/misaligned connectors for the panel ribbons.

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

Ok thanks. Still want to see if I can capture some proper waveforms since I had no luck with the YMain

[mmartell]

Re: Samsung 50" Plasma HPT5044 No Picture

Still thinking something was amiss I went to take measurements of VS/VA/Ve/Vsc. No Ybuffers attached. On the PS, VS and VA measured bang on. Ve on the XMain board measured at 123v instead of the 91v as reported on the panel sticker. Turning the pot had no effect. Beside Ve is VS and when measured there (on the XMain) it was at 213v, 6v more than reported on the PS. When I went to measure Vsc the green light was on the YMain indicating protection. I pulled it and can't find a short.

WTF ???