vp50hdtv10a Buffer testing

[topfli8979]

I have a Vizio p50hdtv10a, what is the proper way to test the ic's on the buffer boards? I have put meter in diode mode, grounded on buffer board then ran all through the pins connecting to the panel. I have gone through 2- y sustains, it works for about a hour then starts flashing screen. So its gotta be the buffers shorting out the y boards.

[tom66]

Re: vp50hdtv10a Buffer testing

Samsung panel? In which case it's unlikely to be the buffers but the power supply going crazy. We are seeing another TV with same symptoms. Nominally 200V output measuring more than 300V! This probably kills the Y-main in short time.

[topfli8979]

Re: vp50hdtv10a Buffer testing

Its a LG panel, voltages are all good. I even thought of the power supply also, replaced with different power board after first y board went. Did the same thing after about a hour. Its destroying the Ipms some how.

[tom66]

Re: vp50hdtv10a Buffer testing

Check the Vs to be sure. It's pretty rare for IPMs to die from failed buffers on an LG.

[topfli8979]

Re: vp50hdtv10a Buffer testing

195.7 vs. Steady. 60 va. Steady

[tom66]

Re: vp50hdtv10a Buffer testing

Hmm, what about the -Vy and Vsc?

[topfli8979]

Re: vp50hdtv10a Buffer testing

199 vsc, 114 -vy

[tom66]

Re: vp50hdtv10a Buffer testing

-Vy looks too low to me. Should be close to -200V. Can you post a picture of the plasma panel voltage sticker?
Also, you need to check Vs when the screen is flickering.

[topfli8979]

Re: vp50hdtv10a Buffer testing

All of these readings are with a good Y main installed, sorry I didnt tell you that, Im just trying to get this figured out so I dont blow another. Only running the set for a few seconds at a time to test. I will get the picture of the voltage sticker.

[topfli8979]

Re: vp50hdtv10a Buffer testing

sorry for poor picture quality.

[drpj23]

Re: vp50hdtv10a Buffer testing

I think the readings just got flipped....but if 114 is vsc then that also is a little low..but not enough to affect anything.

[topfli8979]

Re: vp50hdtv10a Buffer testing

drp, you are right the -vy is -199, the vsc is 114. Wouldn't I need a scope to adjust the vsc?

[tom66]

Re: vp50hdtv10a Buffer testing

I think you need to get -Vy first. -Vy is important for erasing the display, pixels will get stuck on without correct -Vy.

[topfli8979]

Re: vp50hdtv10a Buffer testing

I can do this with a vmeter, just adjusting the -vy pot?

[tom66]

Re: vp50hdtv10a Buffer testing

Yes.

[topfli8979]

Re: vp50hdtv10a Buffer testing

Alright -vy is up -200, +vsc 120. Should I just go for it and run the set, these y boards are so expensive. Nothing else I need to test?

[tom66]

Re: vp50hdtv10a Buffer testing

Just run it.
As SOON as it starts flickering, cut it off.
If it doesn't short then, no damage done.

[topfli8979]

Re: vp50hdtv10a Buffer testing

So far so good, but I am getting red and green sporadic pixelation ONLY in the upper left hand corner of the screen. I know the tv is 6 years old, have seen it on numerous plasma sets. But not in just one corner.

[tom66]

Re: vp50hdtv10a Buffer testing

Yeah, that indicates incorrect Vsc or -Vy, or Setup/Setdn timings, as it ages, you may need to tweak these voltages slightly but NO more than 10V should be necessary.

Sometimes it cannot be resolved without firmware updates made to the control board.