Issues with my "new" '73 Zenith - Videokarma.org TV - Video

ihmeyers · #1 08-11-2010, 12:31 PM

Monday I purchased a '73 Zenith console I found (actually DaveWM found for me) on Craigslist. The owner demonstrated it for me at his house and it had a really strong picture and the colors looked good. When I got it delivered yesterday I notice the greyscale was way off (much too blue). That was a quick fix , just brought up red and green. When I put on program material I noticed a lot of bleeding of blue on some scenes. Not all the time but enough to bother me. This morning I opened up the TV to set convergence and got it almost perfect on the test pattern other than the dynamic convergence on the right side that is off just a hair (didn't have the right alignment tool). Much to my chagrin the blue bleed is still there,not reduced at all from yesterday (see attached). Any ideas? Other than that the colors seem right on.

Ian

P.S. Just degaussed. It didn't do a thing to help...

DaveWM · #2 08-11-2010, 01:10 PM

Man that is off a lot. seems like if it was convergence it would not just be on the side like that but on eveything.

can you get a reg off the air shot, better yet a test pattern shot (cross hatch).

ctc17 · #3 08-11-2010, 01:19 PM

I cant really tell what this is. It looks like a white box in the center of the screen, I even put it in photoshop and tried to crank up the brightness but theres just not enough info.

We need some more shots of the issue with different images.

What chassis is it? Hybrid?

old_tv_nut · #4 08-11-2010, 01:30 PM

Why didn't you turn DOWN Blue, instead of turning up red and green? "Suddenly too much blue" says the blue changed and the output stage is now being driven into saturation.

Tony V · #5 08-11-2010, 01:35 PM

I agree with old tv nut...turn down the blue instead of turning up the red and green.
-Tony

kx250rider · #6 08-11-2010, 02:21 PM

I'd say to start from scratch on the white balance setup... First, turn off the Chromatic switch, and turn down the color all the way. Also turn the brightness to center, and picture to minimum.

If yours is a flat chassis (25DC56, 25EC58, etc): Put all 3 G2 pots to min, green and 2 (or 3 if your set has 3) G1 or Drive controls to mid ***If yours is the upright chassis (23EC45, etc), put the 3 G1 jumpers in the LO position on the video output board, as it has no drive pots. Then throw the service switch. check all 3 G2 pots to see that they don't have burnt spots on them, but turning up slowly and seeing that color line appear slowly with the pot, and not "popping on" like an on-off switch. If it does, (VERY common on those sets), you need to replace the pot before going further.

If all are OK, then turn them up one at a time, until you BARELY see a faint line of each color, and try to get it a FAINT, DIM gray line with the 3 pots. Then put the service switch back to full screen, tune in a program and see if the white balance is better. The white balance should be very close, and you can touch it up by SLIGHTLY turning down the dominant color to correct dark areas of the picture, and use the G1/drive pots or jumpers to correct the brightest areas of the picture. If it's still bleeding blue, you have a weak CRT, and you can probably get away with turning the PICTURE control down a little.

One more tip: If someone has set the Bright Limiter too high (the brightness control won't dim the picture enough with the Chromatic switch OFF), turn the brightness limiter control to where the picture is nice at about 3/4 range of the brightness control. If the picture is good now with the Chromatic switch off, but goes haywire with it on, there are hidden brightness, color and tint controls for the Chromatic function. Those are reached with a long, super-thin screwdriver through the center hole in the Color, Brightness, and Tint control shafts. Be ready to clean those though, as they're usually all dirty from nonuse.

Charles

ihmeyers · #7 08-11-2010, 03:29 PM

I'll try starting from scratch. I had to turn up red and green AFTER turning down blue to balance because the picture was balanced but way too dark.

I have attached some more photos, one the convergence the other 2 from programming where you can clearly see the blue. Seems to happen more frequently in bright scenes which may point to overdriving the tube, no??

Thanks to all.

Regards,
Ian

ihmeyers · #8 08-11-2010, 04:20 PM

Followed Charles' advice best I could. I balanced the set at lower color levels. still see the blue but it is reduced until I turn up brightness and/or contrast at which point it gets really bad. As long as brightness/contrast is down it's not too bad. What does this point too?

Thanks again.

Ian

ctc17 · #9 08-11-2010, 04:32 PM

Is the blue drive/screen up much higher than the others?

ihmeyers · #10 08-11-2010, 04:57 PM

Quote:

Originally Posted by ctc17

Is the blue drive/screen up much higher than the others?

At the risk of sounding ignorant (which I am QUITE good at BTW

), what are the drive controls and where are they? Are those the G2 R/G/B controls on the back bottom of the chassis? Those are all set for fairly low output levels and a balanced greyscale picture.

ctc17 · #11 08-11-2010, 05:07 PM

Yea, are they all about the same or is the blue up much higher?

ihmeyers · #12 08-11-2010, 05:12 PM

No, they're all set about the same.

Back to my observation about contrast/brightness, the fact that when I turn that up the bleed gets much worse would indicate that somehow the blue gun is being over-driven, right?

ctc17 · #13 08-11-2010, 05:21 PM

I have seen this on several sets with weak crts. Its always been red because thats the weakest gun and the red control is all the way at maximum. I have usually been able to mostly get rid of it by backing off the controls and playing with the brightness and contrast.

This does not appear to be the case with you set though. If the controls are all fairly low and you get a bright picture that would indicate a strong crt.

What is the chassis number, I may have the sams on that set.

ihmeyers · #14 08-11-2010, 05:54 PM

Thanks for the help. The set is a SC600x. I can get the chassis # off the back tomorrow if that isn't enough. It's a 25" (I think) CRT and a horizontal chassis.

Ian

kx250rider · #15 08-12-2010, 11:22 AM

That sounds, unfortunately, like a weakening CRT. That's very common, but you can still get that tube from VDC, and maybe Hawkeye since I read here that he's still only partially retired. I strongly recommend against trying to rejuvenate it, since it likely will get really good, then fall off quickly to be worse than ever, after a week or a month.

If you do try to order a tube, ask for a black faced 25VDMP22. That will give a beautiful deep picture on that set; better than the original Zenith tube!

Charles