#46
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focus can be a problem. On some of my sets it seems to be at an extreme end others is fine. On one I had to have the coil turned all the way in (coil used not a pot) and it was still soft, then replaced the focus tube and it was the other way. Same with deal with focus sticks. If you have a supply of focus tubes try subbing in others. Your setup sounds good, so try subbing the video out tube. The pic looks good, if it gets much brighter you will prob start to have some retrace line issues.
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#47
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One of the things I would do is replace that 6EL4 with a 6BK4. Also check or replace the dropping resistor for the 1V2 filament. You're making good progress on that set.
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#48
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I did notice on the 6el4 thats in there, it never lights up, or is so dim I can't see it thru the dark glass even with the room black. As I understand this one only lights up when it needs to?
I don't have full vertical either, Im missing the bottom inch or so, the vertical output tube gets very hot I can't even touch it during operation. |
#49
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Quote:
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#50
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yea you should see the 6Bk4 glow all the time, just brighter when there is less beam current thru the CRT (dark scenes), should be clearly visable glow near the base of the tube. The 6EL4 from what I understand is just more X-ray shielded, leaded glass perhaps. I routinely replace some of the large ceramic tube caps in the vert circuit of zenith, .1 1kv I think. My cap tester only goes to 450v so I cant really test them well. They are prob ok, but I change them anyway. like the other poster said, often there are a lot of minor problems, just need to work them one at a time.
Make sure your pic is centered, do this in the setup mode to see where the horz line is. then you can adj the V heigh and V lin. get that and the purity all squared away before touching the convergence. |
Audiokarma |
#51
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If you mean the blue tube glow, it should only do that when the screen is dark. If it's lighting up strongly all the time, you probably need to do the HV regulation performance check. It involves placing a 1ma current meter in series with the regulator cathode, turning brightness all the way down, then adjusting the HV pot for a .8ma reading. Any more than that and the regulator is dragging down HV too far.
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Evolution... |
#52
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I was meaning the reg orange glow of the filament, I have seen some ghastly green glow on some shunt tubes, perhaps that is a gassey tube. I generally will set up the HV to about 23kv, which works out to about 1-1.5ma shunt tube current with the CRT cut off, and the current on the HOT at specified amount (185-210ma generally). With full raster, the shunt is around .3 to .5ma with very little flux in the HV 23kv.
I have read that if if the shunt current drops below the low amount on the full brightness, then turning the horz eff coil CW 1/4 turn will bring it back up (and increase the current above the min dip amount in the HOT). the idea being if the current thru the shunt drops too low it will be less able to regulate the HV. But the HOT current should still be within the specified max. If all that does not work then there is a problem somewhere in the HV circuit. I know there has been some discussion on what the HV should be set at, I like to keep it no higher than 23kv, the idea being its less likely to arc over in the HV section of the FLY. |
#53
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I'm gonna have to check again but I'm certain I don't see a filament glow on he shunt at all either in the original or the NOS replacements I've tried.
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#54
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Ok feel kinda stupid
The shunt tube was dead. I stuck in a NOS one and it works. All the adjustments had to be done again. Now the HV adjust pot actually does stuff. Pic is sharper and odd blue glows from the 1V2 and the damper are gone. But the shunt does glow blue. (along with a red filament now) Does that mean the HV would have been going full tilt all the time? |
#55
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Yup! I once disconnected the shunt on an Admiral and turned down the brightness, and the HV shot up from 25 to around 30KV and there were lots of new arcing sounds.....Needless to say I did not run her that way long.
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Tom C. Zenith: The quality stays in EVEN after the name falls off! What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4 |
Audiokarma |
#56
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The first color sets had very strong HV sections, both my 21-CT-55 and CTC-4 will make upwards of 40Kv is the regulator is disabled. The later sets were a bit weaker, I once had a CTC-9 that would only make 32Kv with the reg disconnected and my current CTC-7 project won't make much more than 25. I've heard the CTC-5 is the worst of the lot, most schematics show 19.5Kv as the anode supply.
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Evolution... |
#57
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Some of the "popping" may be coming from the old dried out anode cup on the CRT. Zenith used rather small ones that when cracked would arc to the surrounding area of the anode button. These did deteriorate and be sure to look at it. Possibly you may want to replace all of it to the 3AT2 HV socket with a quality cup. Taking a air hose and blowing out the set is a good idea and wiping down the CRT with Windex esp around the anode button helps too. All of that dust/dirt attracts moisture.
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julian |
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