LG plasma MZ-42PZ44 YSUS short

[PowerAmpFreak]

Re: LG plasma MZ-42PZ44 YSUS short

Without having the board in front of me, but as I remember there are 4 trimmers and 4 different voltage regulators on the board.
I'll check each of them.
Wiz, is it logical that the screen behave like this if any of the voltages is incorrectly trimmed?

[Wizard]

Re: LG plasma MZ-42PZ44 YSUS short

These top and bottom pots are only for adjusting the correct "on-length" pulses and is kind of critical. This is why I suggest adjust these to original setting and see. That's on YSUS board itself.

Otherwise need scope and service manual for particular panel not the maker of the TV.

Oh, are you getting red or green sparkles? This is either underdisffusion or overdisffusion. This is on two pots on power supply for Va and Vs. Adjust these slightly after 1/2 hour warm up.

Cheers, Wizard

[PowerAmpFreak]

Re: LG plasma MZ-42PZ44 YSUS short

I'll blindly follow your advice. Will be back on Saturday checking this out.
Yes, there are red/green sparkles actually.
By the way, I've got another set (A sony) using the same YSUS board with green sparkles, this may also be fixed by adjusting the powersupply then..
I'll report the results, thanks a lot, Wiz

[NxB]

Re: LG plasma MZ-42PZ44 YSUS short

I had sparkles too and adjusting the 2 pots helped a little. They went away completely when I input the DVI signal.

[Wizard]

Re: LG plasma MZ-42PZ44 YSUS short

Which pots? Diffusion (sparkles or black sparkles) issues is related to the voltages for the Va and Vs from the power supply. It is characteristic of the plasma panel needing different voltages as they age.

Cheers, Wizard

[NxB]

Re: LG plasma MZ-42PZ44 YSUS short

I adjusted Va, Vs and the pots on the ysus. The ysus pots took out most of the sparkle but also affected black level.

[PowerAmpFreak]

Re: LG plasma MZ-42PZ44 YSUS short

I trimmed the Va and Vs voltages according to sticker on panel. Va 65V and Vs 187V. Screen is very good...most of the time. The green sparkles is all gone after adjusting Va and Vs. Unfortunately something is not perfect, because once in a while the screen fades out, randomly, sparkles and comes back.
It can run for one hour without any problems, but suddenly it behave weird and picture comes back again...
The pots on the new ysus board is set like the old board, so this is not the problem. I believe this is related to another problem in the tv and doesn't have much to do with the ysus board, right?
I'll check with the owner how far he will go with this tv.

[PowerAmpFreak]

Re: LG plasma MZ-42PZ44 YSUS short

The TV may operate correctly for a while, draw approximately 300W from the mains. Suddenly the screen goes out (just like turning down Vs) and random pixels and lines are shown on the screen for a while. Then screen goes all black and set only draws 125W from the mains. Va and Vs supplies and +5V are still up and running during fault condition. Any advice?

[NxB]

Re: LG plasma MZ-42PZ44 YSUS short

Something overheats.

[PowerAmpFreak]

Re: LG plasma MZ-42PZ44 YSUS short

No, it can't be an overheating issue since the time the TV works correctly from starting it may vary from not-at-all to 2 hours. So there are nearly 200W less power consumption when the failure shows up.
Also, I think the YSUS module decrease in temp on the heatsink as the failure is present.

[PlainBill]

Re: LG plasma MZ-42PZ44 YSUS short

No, it can't be an overheating issue since the time the TV works correctly from starting it may vary from not-at-all to 2 hours. So there are nearly 200W less power consumption when the failure shows up.
Also, I think the YSUS module decrease in temp on the heatsink as the failure is present.

Then the other possible cause - a bad solder joint somewhere.

PlainBill

[PowerAmpFreak]

Re: LG plasma MZ-42PZ44 YSUS short

Regarding bad solder joints - I've examined the powersupply board extremely careful and it's OK if solder joints are concerned, so I suspect other boards. What is the result if there are a problem with the Z module? Could this lead to 200W less power consumption and a completely black picture? Besides, when the failure shows up, screen shows random pixels and lines before it goes completely dark.

[PlainBill]

Re: LG plasma MZ-42PZ44 YSUS short

Regarding bad solder joints - I've examined the powersupply board extremely careful and it's OK if solder joints are concerned, so I suspect other boards. What is the result if there are a problem with the Z module? Could this lead to 200W less power consumption and a completely black picture? Besides, when the failure shows up, screen shows random pixels and lines before it goes completely dark.

If I recall correctly, the set draws less power on a black scene. The random pixels and lines would indicate a problem with the main control card, or somewhere upstream in the small signal board.

I just verified this. The plasma set I checked draws 3 watts when turned off. On a (nearly) black screen it draws 135 watts. Tuning to a broadcast channel the demand jumped to 225 - 235 watts. As I recall, the maximum rated draw of this set is 275 watts. So, yes, a problem in the signal path could be the cause of the drop in power consumption if it causes the screen to go black. Perhaps another (better?) way to say it is "Anything that causes the screen to go black will cause a drop in power consumption" (except an arc in the power supply).

PlainBill

[PowerAmpFreak]

Re: LG plasma MZ-42PZ44 YSUS short

Thanks for your info Bill, very good for me to know. So this sounds like the "power parts" are behaving correct and the problem is logic/picture signal loss, as you say.

[mbates14]

Re: LG plasma MZ-42PZ44 YSUS short

or the issue that caused the shorted y-sus, your now observing it. could be an intermittent short in the buffer causing the protection circuits to cut the Y-sus regulators off, then back on. hence why your screen goes black. then comes back. i had the INFAMOUS magnovox plasma do this before the buffer IC blew completely out, blowing out the mosfet bank in the Y-sus board.

replacing the mosfets, and getting a new buffer board fixed the issues on the maggie.

[PowerAmpFreak]

Re: LG plasma MZ-42PZ44 YSUS short

Thanks for your post, this may be the case.
I think I've got two other buffer boards which I will try out. If the problem is still there chances are present buffer and Ysus board is ok.

[Innov8tive1]

Re: LG plasma MZ-42PZ44 YSUS short

Hi all, I am having very similar issues with a Prima plasma which uses the LG boards. I replaced the Ysus with a rebuilt one from E-Bay from a place in Cali. that has 100% pos. feedback. Very reasonable price but he does require a core to be sent back to him.
So anyway, put in the new board and the set fired up (was dead with blown fuse on Ysus before, just like the one in this thread) but the picture was good sometimes and would show sparklies or show kind of a shadowed pixelated image of something that was on the screen a few minutes ago. But next scene everything looked perfect. After running it about 20 mins to warm it up before adjusting anything I heard a "pop" sound and it died again, took out the Ysus fuse and there is a dead short between Vs and Ground. I can only conclude that it is the hybrid as I can not find another shorted component anywhere else on the board.
I called the company I bought it from and he says it is likely one of the buffer boards. I looked them over very carefully and can find no craters or any other damage on any of the ics. Sounds like he will replace the board as their stuff has a 3 month warranty which is good! I will also be sending him my buffer boards and he will test them and sell me a replacement for whichever one is bad.
Sounds like if the Ysus keeps blowing then it's gotta be one of the buffer boards. Hopefully this helps someone.........hopefully it helps me!

[PowerAmpFreak]

Re: LG plasma MZ-42PZ44 YSUS short

Great thanks for that info! Yes, it sounds very similair to my story..
I had two other buffer boards (from another working TV) with identical part numbers which I tried to put in the LG. GOSH!! It's a REAL PAIN to get the flatwires into the sockets on the buffer boards back.
There must be some trick to achieve this...
The flat's are so short there are next to impossible to get them in place and lock the socket.

[Innov8tive1]

Re: LG plasma MZ-42PZ44 YSUS short

I agree about the flat wires. They are very difficult to put in. And you want to be very careful with 'em! I can't believe how many there are in these sets and that there aren't more failures due to broken connections. Lots going on in there!!
When I get the boards back I will definitely post a follow up.

[PowerAmpFreak]

Re: LG plasma MZ-42PZ44 YSUS short

Said and done, tried two other buffer boards. >No improvment<
Picture is still giving me a headache, fades in and out, bla bla bla....
Think if the YSUS board I bought on Ebay is actually bad and cause this? Hmm.....