LG42X3 panel question

[PowerAmpFreak]

Hi all.
I'm working with a LG 42X3 panel fitted in a Fujitsu plasma. Problem was a shorted IPM on the Y-SUS. This one is using the STK795-811A (YPPD-J014C).
It was replaced successfully.
When powering it up, I read all operating voltages OK. I also monitor the power consumption of the set and in a few seconds the power meter shows 635W (!!!) when I as quick as I could, disconnected the set from mains.
The power meter is reliable, it's no problem in measuring, since this power meter shows both appearent power and effective power simultaneously, together with power factor.
First throught was that Z-SUS had a failure, so I carefully measured across the IPM and that measures fine. But, when Z-SUS is disconnected, the power meter shows only 100W, which should be quite normal.
So, my question is, is it big chances that the Z-SUS IPM is bad anyways?

[PowerAmpFreak]

Re: LG42X3 panel question

Oops, just a correction. The IPM was the STK795-820 (YPPD-J018). This is used on both Y and Z-SUS.
Problem is still present. When having Z-SUS in circuit set draws 635W quickly.
It looks I need to replace the Z-SUS IPM aswell, don't you think?

[tom66]

Re: LG42X3 panel question

I'm not sure 635W is abnormal. I have a 42" standard definition plasma here (mid 2003) which is rated for 600W.

[PowerAmpFreak]

Re: LG42X3 panel question

I'm not sure 635W is abnormal. I have a 42" standard definition plasma here (mid 2003) which is rated for 600W.

Well then, I might let it be on for a while. I never saw this much power consumption before so I directly thought this was indicating a problem.

[dumpystig]

Re: LG42X3 panel question

Wiki:

Plasma displays use as much power per square meter as a CRT or an AMLCD television.[citation needed] Power consumption varies greatly with picture content, with bright scenes drawing significantly more power than darker ones – this is also true of CRTs. Typical power consumption is 400 watts for a 50-inch (127 cm) screen. 200 to 310 watts for a 50-inch (127 cm) display when set to cinema mode. Most screens are set to 'shop' mode by default, which draws at least twice the power (around 500–700 watts) of a 'home' setting of less extreme brightness.

[PowerAmpFreak]

Re: LG42X3 panel question

Appearently I was a chicken, when power meter showed 635W I unplugged the set from mains in panic, afraid of blowing the IPM again.
But my fear was not necessary, cause the peak of 635W just last one or two seconds, then power consumption goes down to 300W.
So, this was a successful IPM replacement on Y-SUS board.

[dumpystig]

Re: LG42X3 panel question

Happy days pal

[cadiman]

Re: LG42X3 panel question

Full white for that panel is around 300 watts (warmed up) if I remember.

Start up could easily be more than double.

Make sure you have good stable 15 v to that new ipm. The caps near the ipm fail due to the heat.

[PowerAmpFreak]

Re: LG42X3 panel question

According to the pcb silkscreen I noticed two supplies for the IPM. One +15V and one +18V. I haven't verified the voltages in those nodes but I will make some measurements. Do you think a simple DC voltage measurement will do, or do I need to hook up my scope to it? I would suspect quite a lot of high frequency ripple in these points even if the caps are good, caused by the high gate and bootstrap charge currents inside the IPM.
I might replace the caps and verify the DC levels as a middle way.

[PowerAmpFreak]

Re: LG42X3 panel question

The silkscreen was wrong! On upper side of pcb the silkscreen says +18V and bottom side +15V. The IPM requires only one supply voltage and the correct one is +15V. This measures fine.
Today another plasma came in, with an identical Y-SUS damage. Old IPM now successfully removed. This is starting to be fun!