Slightly greenish raster - Videokarma.org TV - Video

NowhereMan 1966 · #1 02-06-2009, 10:20 PM

All,

What can cause a slightly greenish raster in the picture of a CRT TV. I did notice it a little on my 1982 Zenith System 3. It seems to really do it on one of our local channels more than others but I did adjust the picture to take most if it out. Still, we used another set and the TV station is slightly greenish in color. Still if it is the Zenith could it be a bad board or picture tube?

Many thanks

radiotvnut · #2 02-06-2009, 10:44 PM

The tube is probably showing it's age a little. Turn the color control to minimum. If you notice a green tint, you may need to tweak the CRT bias controls. Those should be located on the 9-181 module. I think I remember some early '80's Zenith's having an auto kine bias (AKB) circuit, meaning there are no bias adjustments. About all you can do in that case is tweak the G2 control on the flyback.

Tinman · #3 02-06-2009, 10:50 PM

This is an observation, AFTER you make sure your greyscale is correct on your set.

I have noticed the greenish tint in quite a bit of "DITITAL" content lately. I Color calibrate broadcast (engineering) monitors, so I sometimes take a double-take when I see this. I check for perfect greyscale and it's dead on. So there IS a green push in some of the converted programming. It seems the techs just don't give a crap about what goes out on the air these days.

zenith2134 · #4 02-06-2009, 11:27 PM

Greyscale/Background is a pretty crucial adjustment that should really be performed on all sets this age.

You'll notice a general improvement; in particular dark scenes. That is, if the greyscale is indeed your problem.

My SZ1927W (9-181) had AKB but I was lucky since it was doing its job just fine.

NowhereMan 1966 · #5 02-07-2009, 11:22 AM

Thanks guys. I wish I had test equipment or even a DVD so I don't exactly know what the proper greyscales are. I did fiddle with it this morning using the controls on the front of the set and got a good picture by screwing around with the tint, picture level (brightness), color level and black level (contrast). On black and white programming, I noticed the greys are softer than the 2006 RCA on top, maybe there could be still a little bit of green hiding in there, I'm not sure, but it isn't green as it was. Maybe the tube is showing it's age a little, it's from 1982, but on color programming, I really don't notice it. If fact, I think I adjusted the picture to where it looks better than the RCA now.

I know I can get aftermarket and/or refurb parts for it on the internet, I wonder if I could get a new tube for it. Hopefully with it being a 1980's era set, I can, either a new tube or there are still plenty out there.

BTW, I've noticed a lot of greens on some programming on my 1702 Commodore monitor with an ATSC tuner so I think the problem is at their end too.

zenith2134 · #6 02-07-2009, 11:48 AM

If you were able to find a new tube for this set, I doubt you'd be able to find a TV shop willing to do a tube swap. And if they were willing to do it, they might charge you some astronomical price.

Again, radiotvnut has given you good advice. Set the color control to 0, for a b&w picture, tint at half, contr and brightn at half, then adjust the r/g/b bias for a black and white picture. (black areas such as letterbars should be black, not tinted) Use a DVD or program with letterbars at the top and bottom of the raster to make it easier. Good luck!

NowhereMan 1966 · #7 02-07-2009, 04:18 PM

Thanks to all although if anyone else wants to chime in, go ahead. I might have to go inside the set to do that but for now I think I got most of the green out by adjusting the front controls. Tinman does have a point where some programming sent digitally something leans towards the green side so I do see from time to time it could be the station too, KDKA-TV here in Pittsburgh does that. When things are good, usually at night, I can get WKBN-TV from Youngstown, also a CBS station, and they were not as green.

bgadow · #8 02-07-2009, 09:50 PM

I remember that in the 80s Consumer Reports always seemed to complain about Zenith sets having a green tint. (at least that is how I remember it) I haven't really noticed it on the ones I've seen, though.

NowhereMan 1966 · #9 02-08-2009, 11:20 AM

Yeah, so far, I managed to get most of the green, if not all of it out, by adjusting the front controls. I only noticed green on KDKA-TV so far, sometimes it clicks in for a sec and then it goes out on their OTA DTV signal. Right now, I have a beautiful picture, almost like it was when it was new although the old girl might show her age from time to time. I think the green is only partially the set's fault as it was said before, sometimes the stations can get their color mix a bit off too.