Hitachi P50V701 VA/VS voltage and maldischarge questions.

[Shinju]

Hey all

I am coming back to this set as I have nothing left to fix!

If you all remember I bought this off craigist about 4-5months ago, the bottom buffer was shot, panel fired up with bottom buffer unplugged only showing the top of the screen with lines.

Fastfoward to today. I reseated the Y-buffer ribbons and what would you know the top part of the screen is whole again.

Good news top buffer is good I think. So now on to the rest, when the TV is in no signal mode there is no noise in the blacks and the HDMI white text looks fine.

When I apply a signal or hit TV guide to display graphics I see maldischarge on lighter colors, blue, greens and I think red sparkling.

I checked the VA and VS and they are almost if not double of what they should be.

Sticker 89/68, meter 190/130.

Is this because only have half the screen is playing? Is the Ysus/Xmain damaged?

Here is a photo of the PS, I will upload the rest in a bit.

[Shinju]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

Did some photoshop enhancements to see these better.

I think I am just going to send the original lower buffer in to get repaired, its beyond my capabilities right now for those tiny little legs!

[tom66]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

These power supplies will remain in regulation even with no load. So I suspect your fault is that someone has adjusted the voltages, possibly from the service menu. You must be careful, running with high Va can damage the panel, and high Vs can damage the Y-sus and X-sus boards.

[Shinju]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

Tom66, do you know how to access the service menu on a Hitachi? I once I get the new buffer/repaired I will disconnect the Xmain (ymain piggy backs off it) and look and see what POTS adjust those voltages.

I will also replace the battery in my Voltmeter and see if that changes its been awhile since I have done so it might be getting low and giving me false readings. Although when I tested the input to the PS it was reading 121ac just fine.

Thanks for the reply!

[tom66]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

I have no idea. I don't work on Hitachi plasmas because of a few bad prior experiences. Maybe in the future.

[Shinju]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

Seems turning the pots on the ps didn't make much of a difference I did however see a drop in voltage when I turned the screen power from max to min ect.

I will update with photos of the pots ect later on.

[Shinju]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

Here are some photos of the PS pots and voltage sticker.

I am not sure what to make of this.

VR380 (Ysus) ?
VR580 (Xmain)?

VR251 (?)
VR151 (?)

Seems like when I adjusted VR580 the screen would get dark/washed out, VR380 would get brighter but never dim.

If I adjusted VR580 to low the panel would shut down and 3 blink.

Either way the voltages never got close to what the sticker said it should be, voltage seemed to be doubled.

[tom66]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

So just to make sure your meter is ok, can you check DC volts on the 200V range on a 9V battery.

[Shinju]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

So just to make sure your meter is ok, can you check DC volts on the 200V range on a 9V battery.

Voltmeter was fine, it was the same one I used to adjust the VA/VS on the pn43d450a2d and those voltages matched up. I replaced the battery too, same results.

Power supply toast?

[tom66]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

I am not sure. It could also be a digital board problem as that board can adjust VS/VA via the various control signals.

[Shinju]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

Ah good point, lucky the majority of parts for this beast are cheap (minus the buffers). With the screen Cell intensity being set to min in power save settings the voltages got close to what they were supposed to be but still high.

I left the panel on for about 30-40 min while testing and the X/Y never got excessively hot they were Luke warm. But that is with half a screen running.

I couldn't get the unit to turn on with everything but the PS/MB disconnected it kept throwing a blink SOS.

[tom66]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

I'm not aware of any plasmas that adjust Vs/Va with display brightness so you might have a PSU problem too.

[Shinju]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

The Samsung PN43 when adjusting the VS voltage I dropped the pot to min and the screen got dark/purple.

I have a buffer repair going, I will see what happens when both are plugged in. If it dies I will scrap it, this thing is HEAVY for being the last gen Hitachi plasma!

[tom66]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

That's normal. Plasmas "pink out" when the Vs drops out - this is because green and blue wavelengths require more energy than red.

[Shinju]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

That's normal. Plasmas "pink out" when the Vs drops out - this is because green and blue wavelengths require more energy than red.

Gotcha, probably be my last Hitachi, too much craziness going on with them!

[tom66]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

I had one Hitachi 42" 42PD6600 on my bench once. I unplugged Y-sus and X-sus to diagnose... this put the set into a fault mode from which it never recovered.

The power light blinked an error code as expected. But there was NO WAY to reset after this, it never worked again, I checked everywhere. Some combination of keys? Nope. Unplug and power off? Only solution was to replace the entire digital board.

[Shinju]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

That's no bueno!

Yeah I was worried about something like that or just blowing up a X/Y board but this think seems to want to keep going.

Seems like it was a pretty good plasma panel in its time that's why I picked it up. I hope I can at least get it close to what it was in its glory days!

[tom66]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

Hitachi panels were pretty average.

Up until late, they didn't even do a full 1920x1080p - just some weird 1080x1080 or 1280x1080 resolution. WTF? They are also interlaced displays, which is noticeable on moving content. And they have pretty mediocre black levels.

So meh... I'm not a big fan to be honest.

[Shinju]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

YES! I noticed that on some other Hitachi PDP panels. This one does 1920x1080p, and crazy enough as I have gotten so used to 120hz LCD panels I was watching a scene in Avatar that shows off 120hz really good on sets that have that FRC.

This Hitachi in that same scene felt like it was 120hz it was ultra smooth, but again this is with only halfscreen so I cannot judge anything yet, but it was pretty smooth all around I don't know if this is 600hz or 480hz field drive.

[tom66]

Re: Hitachi P50V701 VA/VS voltage and maldischarge questions.

I can't be the only one, but I hate the effect created by 120Hz features. It just makes films look weird.