Help! My TV Is Displaying A Band

[David Meek]

Just like it says in the title. My Pioneer RPTV has started displaying a vertical band that is about 3 inches wide and positioned just a little right of the center of the screen. It's only visible when a plain dark gray background is shown (when there is no signal being displayed). The band is slightly darker than the rest of the background. It only started a few evenings ago.

I've adjusted the set using Avia and Video Essentials so the contrast and brightness are set properly. Any thoughts? Should I be concerned?




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[Kevin P]

Does it appear only when there's no signal? If you bring up the Avia or VE gray fields, does it appear in any of them?

Is the band a different color than the rest of the screen, or is it the same gray, just darker?

KJP




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[Lex]

I have no clue what this is. Jon?
Doesn't sound good though. Bummer.

Aren't you glad I resisted temptation to ask if you were on MTV? Get it, band? :roll:

Lex

[David Meek]

Kevin, good idea. I'm heading home so I'll check it. Thanks.

Lex, phonetically in Texan, I should have titled this thread: Hayelp! Mah tayvay is dis playin' ah bayand.




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[Lex]

lol David. I had one display a fatal color bar vertically once, basically, a serious thing. I took it back.

Lex

[David Meek]

I ran through all of the advanced video display screens on my Avia disk last night. The bar doesn't show up at all on any of the screens except for the full screen blue color, and then only VERY slightly. I doesn't show up on the DVD intro screen from my Panasonic DVD player. It does show up as I said earlier in the blank gray screen I get when there is no signal running to the TV. It's a slightly darker gray than the rest of the screen.

Any more thoughts? :sos:




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[Kevin P]

At first I thought you might have a phosphor burn on your blue CRT but then you'd see the band on the Avia gray fields as well as blue. I wonder if the set is picking up interference or some kind of ground loop somewhere (though this usually causes horizontal lines, not vertical).

Did the band appear after you made some change to your system? Try disconnecting cables one by one from the TV and see if the band disappears.

Or just don't worry about it--if you don't see it in normal viewing I wouldn't sweat it. If it gets worse, then call in a tech.

KJP




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[David Meek]

if you don't see it in normal viewing I wouldn't sweat it. If it gets worse, then call in a tech

Kev, that's what I'll do unless someone posts an "Oh, my god no!" response. My "retentive" side made me ask the question though. I wanted to get this diagnosed and make sure it wasn't a serious issue. I'm really concerned about burn-in and it's associated evils.




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[George Bellefontaine]

Oh, my God, no ! :LOL:

Seriously, Tex, just wondering how long you've noticed this problem. I've read somewhere that some RPTVs have shadow problems. Probably some kind of reflection inside the baox between the mirrors and the crt tubes. Some people have had to line the insdie of the tv with dark cloth. But if this was the problem, I'm sure you would have noticed it from day one.




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[Lex]

Ask Pioneer David, see what they say. Is it still under warranty?

Lex

[David Meek]

George, it's only been around (that I've noticed) a few days. Yeah, the duvetine lining is something I'll eventually do, but I want to get it "ISF'd" first.

Lex, yeah it's under warranty for 3 more years. Replacing one gun one time would pay for the whole extended warranty! Seemed like cheap insurance at the time - and now.




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[brucek]

David,

Your fault could certainly be caused by many things. My best advice would be to put in a service call on it, because it's not likely to go away and you do want to ensure you have it repaired under warranty.

I can discuss some possibilites with you, but again since it's under warranty, I don't think you want to touch it.

It's not likely vertical or horizontal deflection or even convergence because your raster seems to be proper and not distorted in any way. Sometimes you can get folds in the deflection waveforms and the result is a darker or brighter raster in the offending area, but usually also results in obvious distortion of the video signal at that point also. This then assumes that the power supplies for these circuits are likely OK and also says the HV supply is also OK since your overall raster hasn't shrunk or expanded..

I wouldn't put too much store in the fact that you can't see the fault when video is applied. It may still be there, but the video signal overwhelms your ability to see it. I won't go into the whole boring story of how a CRT works, but when no (AC) video signal is applied to the cathode of a CRT, the CRT's (DC) biasing to the cathode, G2, G3 and anode HV are set to "just" bias on a raster that is barely visible.

In this state, (assuming a flat AC baseline from the video drive amp), when any AC video signal is then applied to the cathode, the electron beam will brighten that phosphor spot on the screen. So, for your situation, it's in this, "no AC video, DC biased on" condition, that you're seeing this grey vertical discoloration on your screen, and only on the blue gun.

Since most of the DC bias voltages for the CRT's are initially common, I wouldn't think it was any of these at fault, although perhaps a small capacitor specific to the voltage as it feeds the specific CRT . It could also be a distorted "no signal" baseline from the video drive amp for the blue gun - capacitor defective. These amps usually plug on and hang underneath each CRT, so they're easy to replace.

It could be as simple as something fallen on the lens face inside.
If it was coolant contamination in the fluid chambers, the result would more than likely be distortion, rather than a darker than normal band area.

It would be nice to get a visual look at each of the CRT faces with the RPTV opened up. Then you could get a visual of the raster without any video applied and see if it's specific only to one gun. Again this is something you don't want to do because it's under warranty.

Generally, RPTV repair has been reduced to quick board swapping, eliminating any real necessity for discussing what's actually at fault. This seems to be the most efficient way to repair things these days. The CRT's are the only thing that will take any time to replace, but no big deal if they're under warranty.

Anyway, it's a positive thing that your fault is consistantly repeatable and demonstratable, so you'll have no trouble proving your case to the repair person. These types of fault are far better than the intermittant variety that always seem to disappear when you try and demonstrate them. h:

brucek

[George Bellefontaine]

Tex,
Sounds like good advice from Bruce. He really knows his stuff. In fact, I just learned a few new things about crts.




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[David Meek]

Bruce,

Thanks for the advice and the primer! More information is ALWAYS good as far as I'm concerned.

One more question: I'm about to take the whole system down for about a month while I renovate our dedicated (sorry Lex ) HT room. I'm thinking it would be better to wait on the service call until I get everything completed and the system in place in its permanent configuration. Is that a better choice than calling out the tech immediately? This is just a concern that the new layout might introduce other issues that'd need to be looked into.




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[brucek]

david,

Oh for sure, I would wait until the HT room is setup.
This is something that likely isn't going to go away. My suggestion was that you don't "just live with" this problem, it deserves reporting under warranty..

brucek