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  #1  
Old 09-24-2011, 01:46 PM
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old_tv_nut old_tv_nut is offline
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Zenith "coffin"

The beast arrived, courtesy of "aerials."

Tim and aerials did most of the grunting

P9240005 by old_tv_nut, on Flickr

The tube has a cataract, but the filaments are open, so I don't have to fix the cataract

P9240009 by old_tv_nut, on Flickr

Fortunately I have an excellent tube in the console I got from miniman, along with a reasonable backup.

P9240002 by old_tv_nut, on Flickr
P9240001 by old_tv_nut, on Flickr

Both of these are separate glass type, with the gasket that turns to ooze after all these years, so cleaning and retaping is all that's needed, as I understand it.

By now you should know that I go at these things slowly, so expect occasional progress reports.
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Old 09-24-2011, 08:45 PM
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now I have to look for some service info - and I have to back up and figure out the model numbers and chassis.

The coffin is Model 7500-3 (?) and the rest of the printing is smeared, but it looks like chassis 11L8T25Z (??)

The smaller console doesn't seem to have a visible model number and I haven't determined a chassis number either.

Is the chassis number stamped on the chassis somewhere?
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  #3  
Old 09-24-2011, 11:17 PM
Steve K Steve K is offline
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Wayne:

The TV chassis should be something like 24MC23 or 25LC something. I believe that the 11L8... number is the radio or amplifier chassis. Unfortunately my Zenith service info for that set is in Wisconsin.

Steve

Last edited by Steve K; 09-24-2011 at 11:23 PM.
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Old 09-25-2011, 12:06 AM
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miniman82 miniman82 is offline
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The number for the set you got from me is located near the HV cage, should be 25MC33 just like the other.
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Old 09-25-2011, 11:14 AM
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Quote:
Originally Posted by miniman82 View Post
The number for the set you got from me is located near the HV cage, should be 25MC33 just like the other.
hmm - do you have to pull the chasis to see it?

Also, the chassis are not identical - the coffin has the power transormer at an angle and has what looks like a compactron in the section down under the CRT.
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Old 09-25-2011, 11:42 AM
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By the other, I was speaking about the one I got at that same estate sale. There were 2 sets and a spare chasiss, all the same. I can't speculate on what your huge combo has in it, pictures usually help and Mark would know best of all just by seeing it.
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Old 09-25-2011, 11:49 AM
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Does this one have UHF tuning? Sounds like the chassis sticker is missing, they are always on the HV cage facing the back of the set and they are pretty big so you can't miss them if they are still present.
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  #8  
Old 09-26-2011, 09:20 PM
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Pictures of the combo:

P9260012 z combo by old_tv_nut, on Flickr


P9260013 z combo by old_tv_nut, on Flickr


P9260014 z combo by old_tv_nut, on Flickr


P9260015 z combo by old_tv_nut, on Flickr

pictures of the console for comparison:

P9260016 z console by old_tv_nut, on Flickr


P9260018 z console by old_tv_nut, on Flickr
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  #9  
Old 09-26-2011, 09:44 PM
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you know years ago I read an article about picture tubes with open filaments. I know some of you are going to poo poo the idea, and you know what you can do, but in I believe it was popular electronics, or radio electronics back in the late 70's when I was rich enough to get magazines. I remember a project for attempting to repair picture tubes with open filaments. If you had a tube with this condition and it was known to be good and worth it, what you would do was hook up yer VOM to the filaments and wack the neck of the tube, and if the needle moved, then it was thought that the filament wire was close to touching, and could possibly be "welded" back together. Now this only worked on B&W or other series filament color tubes. The project included testing the tube for the needle movement, and then if it were moving, the filament pins were then replaced with a charged capacitor, and then the tube was to be wacked again in a way known to always cause the meter needle to move when it was attached. The key was to get a pattern identified where the meter needle was guaranteed to move, that way you knew you could reproduce it and get a weld when the cap discharged when it was across the filament pins. Since I don't have the magazine, you would have to do some thinking, experimenting, praying, or other magic to figure out what cap and voltage charge might produce a good weld, and not burn off the wires inside the tube and make a second attempt pointless. Anyway since the person in this post has an otherwise useless tube, I thought this might be worth a try. Since I am older now, and many of you are smart enough to know about harmonics, here are some additional things to try to make this successful. If you can't get the meter to move with a simple whack, you may want to try adding harmonics to the parts inside the tube to ensure movement. Use a speaker and audio generator, mount the speaker to the tube, and have the sound vibrate the stuff in the tube. Put yer beeper, or cell phone on vibrate and let it vibrate against the tube. etc, etc on any things that can set up harmonics inside the tube's elements. it might also be a cool idea to try and see if you can see the open spot inside the tube before you begin... you know use a flashlight, magnifying glass, clean the neck see what might be available to see. Who knows you might even have to warm up the tube in the sun, whack it to see if you get a momentary continuity, maybe cool it, whatever might be needed to try and get a possible connection. And I'll tell you one more thing I did as a kid. We has clear light bulbs, and on a few occasions when I was less than 20 and with lots of time to learn and do weird stuff, a few times I took those bulbs when they went bad and could see the broken spot, shook the bulb moved it around and got the wire to slide out of the little round filament holders till I got the filament flappin in the unbreeze, and got it to lay across what was left of the other end of the filament still attached to the other post, and wa-la I had a bulb working again.... I carefully screwed them into a socket where I typically got another month or two out of them. Since they were brighter, I assume if I dimmed them a little I bet they would have lasted longer... Not really a concern welding a picture tube filament.
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Old 09-26-2011, 10:06 PM
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I've never been bored or desperate enough to think of trying to wiggle the filament out of the loop, but have on occasion wiggled the filament in the clear decorative bulbs in the bathroom to get a weld and a little more life out of the bulbs when enough are burntout to make the place dim and spooky.

BTW what is that box above the HV cage only present in the combo?
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Old 09-26-2011, 10:34 PM
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I've tried the light bulb trick with some success, myself, and have attempted the charged capacitor trick. While it didn't work in my case, I think under the right conditions it could do well.

The crt in my CTC-15 had one open filament. I tapped lightly on the neck with a screwdriver while it was connected to the tester and the dead gun came to life. I may have had to do it once more, shortly after. Knock wood, no more trouble.
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Old 09-26-2011, 11:48 PM
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The box above the HV cage is the remote chassis.
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  #13  
Old 09-27-2011, 12:19 AM
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Consider this: what are the chances that all three internal-to-the-tube filaments opened simultaneously? I would reckon the chances are pretty small. That is to say I have never come across an instance where the three filaments open simultaneously unless the tube is down to air.

Typically, I would expect a single filament to open at the weld or in the middle. Because the filaments are parallel connected in the tube, a single open filament would mean the other two filaments remain lighted and the picture would shift in hue. Unless the viewer is color blind, the picture would be unwatchable.

I would venture to guess that if the tube filaments test open, the problem could be the solder connection to the pin at the socket.

Wayne: Have you tried running a soldering iron on the filament pins and run a bit of fresh solder?

Incidently that set is a nice find. That was a great chassis and was my first color TV nearly 40 years ago.

Terry

Last edited by Penthode; 09-27-2011 at 12:30 AM.
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  #14  
Old 09-27-2011, 05:56 AM
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In the event of missing chassis number stickers, you can always use the tube location diagram found on the inside of the cabinet as those will also indicate the chassis number. Im guessing your combo to be something around a 25LC20Q
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  #15  
Old 09-27-2011, 09:39 PM
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Thanks for all the hints - had no time tonight, but will get back at it tomorrow.
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