#46
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Those RCAs were built for cost, but I have to tell you, design wise they were very well sorted. There were no "that's just the way they are" performance issues. Even when put behind a 35" tube, they produced a very nice artifact free picture. As far as convergence, all RCAs of that era used a pre-yammed yoke and a flexible magnetic convergence/purity band in place of the mechanical beam bender that everyone else used, and I can state categorically that in the thousands of those I had repaired over the years, I never had a convergence issue on any of them. Generally, a blue outline is a weak CRT, but the halo would not be static: it would change and flare outward with contrast and brightness level. If you see the halo at very low brightness levels, I would say it's not a weak tube. If the tube is strong, I'd lean towards a bad jungle IC causing that. Uncommon but I've seen them. I can't think of anything in the eeprom that would cause that. John |
#47
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Too much Blue in picture Screen shot
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#48
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OK, I see the pic. If you put an image on and freeze frame it (like a DVD), and the blue flaring does not change with brightness/contrast or G2 changes, then it's not the tube (huzzah).
Just to be sure it's not convergence, can you take a pic of the problem showing graphics? With regard to convergence, make sure the picture tube wasn't changed. We were supposed to install a mechanical beam bender when the tube was changed, but lots of us just reused the flexible magnetic tape. You would be surprised how easily the convergence and purity fell into place by rotating and then taping the magnetic strip back down.. I have those schematics at work, when I get there I'll check to see what's involved in the RGB system. IIRC, there are three transistors (r,g,b) off the jungle which drive the three TO-220 transistors on the CRT socket board. I also may have seen this before and logged it. It looks like the blue has very low bandwidth and is causing the blue flare. A trick to split the problem between the main chassis and the CRT socket board or CRT itself is to swap the blue and (say) red wire inputs to the CRT board and see if the flare swaps to red (turn the chroma down). If it stays on the blue, the main board is OK and the problem is at the socket board or tube itself. If the flaring changes to red, we have to work backward to the main board. John |
#49
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The output from the jungle IC goes directly to the kine output board - there are no drivers between them.
At the CRT board, there are three input wires (prob color coded) for the kine drives - E1 (red), E2 (blue) and E3 (green). Remove the blue wire at point E2 and swap it with either E3 or E1 and see if the problem switches color. The only parts on the main board connected between E2 and the jungle IC are a 100 ohm resistor, a 220 pf surface mount capacitor, and a 2.2 uh coil. If the flaring switches from blue to red or green when you swap the wires, you have a problem on the main board, and I'd bet that it's the jungle IC (or what RCA called the T-Chip). BTW, if you put the TV on a blank input and activate the menus, does the blue flaring show up on the menus as well? John |
#50
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Blue Issue
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Audiokarma |
#51
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Turning down the G2 does seem to help some. However, still a little bit visible.
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#52
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Improved Picture
I went back into the Service Menu and adjusted the Drive Adjustments. I turned the blue down, and adjusted the Green and Red as well. I do not seem to have as much blue flare in the picture. It doesn't even seem visible from a distance now. It may have dimmed my picture some and the white isn't as pure by increasing the green and lessening the blue. However, I feel it's better than the blue flare. I will post a picture in my Album of a screen shot now.
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#53
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One odd artifact of eeprom corruption in this chassis series is that sometimes the parameters get pushed way beyond their programmed range. That seems to not make sense but go back into the service menu and lower the blue bias to it's lowest point. Ordinarily, it will go to value zero and stop. If it does, it's acting normally. Under certain conditions, you may find it runs past zero and starts again from the top and runs back down. If this happens, keep pushing the down button until it reaches zero and stops - it may take two or more times. Do the same for the other colors and other features like contrast preset etc. Once each parameter reaches zero and stays there, it will be fine - it can no longer run past 255 or whatever the top number is. Don't touch the horiz osc adjustment because if that goes back to the top value, the HV shutdown will activate (there's a way to recover that, but it's a pain in the butt). John |
#54
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The parameter for each would stay at 0. I’m thinking blue is caused from weak CRT. Blue really flames outward around lettering etc. when TV is set back to original setting of the blue drive & leaving picture level at factory setting. No luck of eliminating excess blue color in some pictures even with picture, bright, & color tweaked way down. The only way to get it as good as I can is leave blue drive & bias down which in turn gives a somewhat greenish cast to white.
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#55
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John |
Audiokarma |
#56
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The blue flares some if you freeze the picture. It helps picture quality & look some if I move tint more towards a Green. The way it’s currently set at Red looks a little more like magenta. The greener tint takes away some of the blue shadowing.
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#57
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Posted two new pictures to my album. I have found, if I turn down picture & turn up bright the blue flaring isn’t noticeable from viewing distance. If you look at picture up close, it doesn’t seem to be as dominant as if TV is ran at Picture Reset.
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#58
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Where is your album and how do I see it? Is it filed at Imgur.com? Thanks much.
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Jeff, WB8NHV Collecting, restoring and enjoying vintage Zenith radios since 2002 Zenith. Gone, but not forgotten. |
#59
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Pictures should be able to be viewed if you look under my user name.
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#60
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I found them. Thanks again. Did you just start this album recently? I ask because I found only two photos in it.
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Jeff, WB8NHV Collecting, restoring and enjoying vintage Zenith radios since 2002 Zenith. Gone, but not forgotten. Last edited by Jeffhs; 01-06-2021 at 12:52 AM. |
Audiokarma |
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