CurtPalme.com Home Theater Forum

RogerH · Joined: 14 Jul 2010 Posts: 64 Location: Minneapolis

I've tried searching for information on two questions (two separate items) but I seem to be pulling up answers to different issues, at least on the question of glow. This is NOT the residual glow that some people observe when they turn their sets off. The other question regards some analog-ish banding that I am seeing.

I am new to plasmas (although not new to LCD/LED or CRT), and I just picked up a new Panasonic TC-60ps34. Not high end by any means, but cheap, and it had pretty decent comments.

Issue # 1

I was under the perhaps mistaken impression that plasmas would go really black compared side-by-side with a non-dimming LED/LCD tvs, but this particular plasma model seems to have a uniform glow in a darkened room that is comparable in brightness to my edge-lit Sony Bravia with 0 IRE input. It is also independent of signal source-it is there on anything from composite to HDMI.

This issue is a uniform, full screen, low-level glow that underlies the actual picture information and is not affected by black level or any user-level controls. It is not an afterglow from a bright screen because it is there even if I turn the set on cold with a black source.

If I put on a pluge test pattern and reduce the black level lower than normal so that no pluge bars are visible at all (and I see no random pixels firing anywhere on screen) there are still discrete lines glowing dimly that look exactly like very dim interlaced scan lines. I wouldn't be surprised to hear that this is normal for plasmas, but it is very real and I did not expect to see anything like it, given the reputation for black blacks.

BTW, I went back to the store and looked at their display model with no signal, and I could faintly detect the same thing even under metal halide lighting, although I'm sure the sales guy though I was insane.

Issue #2

I was also very surprised to see faint but annoying horizontal banding when I have high contrast objects on screen: white credits on black background, bright menu items against gray backgrounds, and so on. Yellow buttons on my bluray player screen cause streaks through the grey background on both sides. I am used to seeing this on CRTs, but I don't know enough about Plasmas to understand how or whether it should be there. The source is known to be clean.

I would have attached a photo of this but it looks just like what is commonly seen on analog displays that have imperfect recovery after video-level transients. I was unable to test this on the store display model.

So my questions are:

Is plasma background glow normal? I guess I was expecting CRT blacks...

Is horizontal banding on high contrast objects part of the plasma technology?

Thanks

RogerH

**Curt Palme** · Posted: Tue Sep 06, 2011 5:59 pm Post subject:

# 1- normal, at least with every plasma that I've seen.

#2- can't say I've seen that, but I haven't played critically with plasmas..

RogerH · Joined: 14 Jul 2010 Posts: 64 Location: Minneapolis

That helps, Curt. One answer like that tells me more than any number of "I've never seen it" replies. The glow itself is usually not an issue when viewing actual content (except during fades to black), but I am surprised that I don't hear more about it.

I still would like to hear if anyone has seen banding, and I may try to find a standard pattern that shows the problem and post a picture if necessary.

BTW, it took me 1hr and 10 minutes to get through to Panasonic, about 15 minutes to explain the questions to the lady writing them down for engineering review, and the promise of a detailed response in 2-3 days.

Or I can ask here and get a reply in a few minutes. Thanks for that.

Tom.W · Joined: 09 Mar 2006 Posts: 6635

The banding could be a ground loop problem.

http://www.epanorama.net/documents/groundloop/index.html

WanMan · Joined: 19 Mar 2006 Posts: 10270

No way to eliminate the faint glow of a black-ish screen in a completely dark room. Plasma requires a precharge condition of the pixels in order that that fire quick enough to be used in video. Trust me, I wish the precharge condition didn't exist, or that SED/FED had made it to consumer electronics.

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Lets add to this.

Do plasmas usually have a poor white? YES

When a component goes bad does it usually take out many more components? YES

If I replace a board that I know is bad and another board is also bad that I didn't know, will it damage the new board? YES

Do plasmas usually cost more to repair then it costs to buy a new one? YES

Do plasmas usually go bad after they are just out of warranty? YES

Do I like plasmas.....? NO

Do I like any digital display device? NO

Have a nice day...... Mr. Green

**AnalogRocks** · Posted: Tue Sep 06, 2011 10:53 pm Post subject:

RogerH · Joined: 14 Jul 2010 Posts: 64 Location: Minneapolis

I am actually a little happy to hear that the glow is normal. It really is not a problem where this TV is going, but I wanted to know if I had a unique problem.

Can anyone explain the reason for the horizontal banding? It's pretty easy to understand in the signal path of an analog display, but I honestly don't know a thing about the plasma architecture from digital input to the display. I should spend some time reading about it on the intertubes, but I thought I'd ask while I was here freaking out about my non-black blacks.

Regarding the wisdom of owning a plasma, I have to say that two days ago I wouldn't have gone near one, but after returning a really bad Samsung LCD/LED to CostCo, my expectations for any flat screen were pretty low. But then I walked by this 60" plasma selling for under $1k, and after researching it a bit I ended up buying it for a bedroom TV, along with a Bravia (which is looking very good) to replace the Samsung. That evening I sat through a blu-ray movie on the 60" screen at a distance close enough to nearly reach the screen with my toes, and I was pretty much stunned at the picture quality.

I'm a latecomer to, and a skeptic of digital displays for TV, and I have no realistic expectation that they'll last even half as long as my old rear projection CRT. But as I walk through my local electronics stores I'm not seeing much suitable for a living room or bedroom that isn't digital, flat, imperfect, and fully capable of crapping out beyond economical repair at any time.

My thanks to those that explained the glow issue. I don't specifically remember reading anything about it, but I had some reason to suspect that it might be normal.

WanMan · Joined: 19 Mar 2006 Posts: 10270

Oh, I am not saying the glow you are observing is 'normal'. If it is due to the precharge condition then so be it. Then again, the voltage level for the precharge could be high (even above normal).