Zenith "coffin"
 

The beast arrived, courtesy of "aerials."

Tim and aerials did most of the grunting
http://farm7.static.flickr.com/6162/...6d9b1586_z.jpg
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 :thumbsdn::thmbsp::pity:
http://farm7.static.flickr.com/6174/...2e8b1e8b_z.jpg
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.
http://farm7.static.flickr.com/6153/...cd7af3fe_m.jpg
P9240002 by old_tv_nut, on Flickrhttp://farm7.static.flickr.com/6153/...5f13808a_m.jpg
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.

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?

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

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.

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.

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.

Pictures of the combo:
http://farm7.static.flickr.com/6166/...d75129bc_z.jpg
P9260012 z combo by old_tv_nut, on Flickr

http://farm7.static.flickr.com/6156/...6263e779_z.jpg
P9260013 z combo by old_tv_nut, on Flickr

http://farm7.static.flickr.com/6163/...439595ee_z.jpg
P9260014 z combo by old_tv_nut, on Flickr

http://farm7.static.flickr.com/6170/...44cf3f26_z.jpg
P9260015 z combo by old_tv_nut, on Flickr

pictures of the console for comparison:
http://farm7.static.flickr.com/6161/...a3de0a30_z.jpg
P9260016 z console by old_tv_nut, on Flickr

http://farm7.static.flickr.com/6178/...2f4a2fea_z.jpg
P9260018 z console by old_tv_nut, on Flickr

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.

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?

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.

The box above the HV cage is the remote chassis.

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

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

Thanks for all the hints - had no time tonight, but will get back at it tomorrow.

Is the combo the one you are calling the coffin?

Ya mind if I ask where you dug it up?

"The box above the HV cage is the remote chassis"
Remote chassis for what?
Phil

Take a wild guess, there's a radio and a TV in it...

Never seen a Space Command chassis in a black cage before and got confused.

I'm smart enough to know what it controls.

Yes, long combo is often called a coffin model.

Aerials, who has been much more than kind and generous, found it and eventually gave it to me based on the expectation that I will restore it, as I did the family CTC-5 that he gave me a few years ago.

d'oh (slaps forehead) -- I did the imitation of a pretzel required to focus my bifocals on the inside of the cabinet, and found the info last night (will post when I get home tonight). I'm going to try snapping a pic of the labels so I don't have to do the human origami trick again.

I think one chassis was a K and the other a L, will post the full numbers.

Here's the coffin diagram, 25LC30. The console is 25KC20U.
http://farm7.static.flickr.com/6135/...78f750ac_b.jpg
coffin tube diag P9280023cr by old_tv_nut, on Flickr

took the back off the stereo side - it is "11L8T25Z chassis", stamped in ink

Possible year of Zenith close?
 

I am thinking 1962 or 1963? Im sure Wayne you will get facts on this monster set. I am still trying to get that ctc-5 up in Auburn, In. I will try to drive up this weekend and beg as best I can. he has vintage B/W sets from the 1950's I have no desire for. You Guy's spoiled me with Color round tube sets. I look everyday to find and rescue another roundie. I thank everyone of you talented technicians to breathing life into historical sets.

Even though your set has chassis 25LC30 it sure looks different from mine. Check out the differences with the convergence assy and the power transformer! What date codes do you see? Mine is a very early 64 before the UHF mandate and no space command.

I've seen the finned power transformers before, never paid attention to what sets they were in. Regarding the convergence coils, is it possible yours were replaced at some time? (I'm guessing mine weren't, since there seems to be the same layer of dust on the tube neck as on everything.)

The 25LC30 is covered in sams 722-4 and my convergence assy looks like the one they show on the rear view pix. Variations are always possible....

Remote chassis
 

Silly me. When I saw "remote chassis" my mind switched to "remote (tuner) chassis", but I knew that wasn't right. About as bad as when I read "General Cement" and my mind switched to "General Concrete". Miniman82, I'd really rather have a Wild Turkey right now than a wild guess.

WOrks for me, take a shot and down some A&W. Sounds odd, but the caramel aftertaste mixed with the Turnkey is glorious.

Put a DTV converter box or cable box on that set and you won't need Space Command, as these boxes come with their own remotes that will operate the set's basic functions -- including on-off in most cases (see my note below). The Zenith DTT-900 and DT-901 are two very good DTV converters from what I've read here (never had any experience with one because my flat-panel set already has an ATSC tuner and remote, though I am presently using a GE universal remote with the TV, my VCR and DVD). Unfortunately, however, the on-off button on the DTT-900/901 boxes won't work if your TV doesn't have remote control, but the other basic functions (channel +/-, volume +/- and probably mute) should work just fine. VK member Electroking in Montreal has one of these boxes on one of his older TVs without remote; the power button on the DTT-900/901 remote won't work on that set either. In these cases, you must switch the TV on and off manually, or else get a switch on a long cord that plugs in between the AC outlet and the TV. I don't know if this type of "wired remote" is still available (I had one back in the '70s), but if you can find one, it will more than compensate for the lack of on/off switching at the converter box remote, although you will need to be wary of the cord. Zenith's first TV remote control system, the "Lazy Bones", was introduced in 1950 and had the control unit on the end of a very long cord; that cord was unsightly and also created a tripping hazard, as it often ran across the room in which the television was located. The Lazy Bones system was replaced with the Flash-Matic remote, Zenith's first wireless TV remote control, in 1955; the Flash-Matic, after only one year (!) and many customer complaints, was replaced by the Space Command ultrasonic remote system . . . and the rest, as they say, is history.

I've got a newer "wired remote" for 120VAC outlets that was bought for use with christmas lights a few years back (the thing is green).

RE: Welding open filaments. I did that years ago back in the 80’s. I have had a few junkers with open filaments that whacking the tube would make it work for a while. I charged a 10mfd cap to 250 volts (no math here I had a 250 vdc regulated power supply and a 10mfd pigtail cap). Wired it up and whacked it! The tubes lasted for years after that. I do recall some color tube filaments being wired in series. I don’t remember what types…

Getting back on track (finally) - I started to look at the set after a long time of ignoring it, and I find none of the tubes are listed on my old Realistic tube tester.

Anyway, my planned order of business:
Test all tubes and order replacements if needed
Pull TV chassis on both sets (coffin and CRT donor console) and stereo chassis on coffin
Pull dead CRT and get rid of it
Pull donor CRT, remove glass and clean/replace gasket
Install donor CRT
Cap census - purchase caps
Recap coffin TV and stereo chassis

Estimated time of completion August??

Besides finding a tube tester, I think I need someone to help put the coffin on its face for CRT replacement.

Chassis number in a Zenith Coffin
 

:banana:Yes, the tube chart in a Zenith would definitely have the chassis model.

That will be a really nice set when you get it going. I just wonder what killed the filament? I've rarely seen dead CRT filaments.

Well, I started to look at this set again, and immediately got stuck. The manuals have nice diagrams of what on the control panel connects where on the chassis, but no instructions on what to disconnect or unscrew from the cabinet to remove the chassis - that is, what has to go with the chassis and what stays in the cabinet, and what do you remove first. Some things have obvious plugs, but others, like the color controls, SEEM to be hardwired to the chassis. So now what?

My planned first step was to pull the chassis so I can swap CRTs and also begin work on caps, but I'm still scratching my head.

Anybody know how this set is supposed to come apart? Am I thinking of it backwards and the bezel should come off somehow first?

look in the compartment up front where the controls are. There SHOULD be 2 phillips screws. Remove the knobs, remove those two screws. The box unhooks in back from the bezel! The power/volume knob is (2) 1/4 inch screws. The speaker unplugs from the chassis. as does the convergence and tuner. Watch the HV suction cup! :) Unplug the yoke wires, and the chassis should ease out.

If it's like my 25LC20, the controls box can be hooked onto the front of the chassis and secured with a screw to hold it in there so it doesn't flop around.

Just look it over carefully, and it's pretty obvious once you do it the first time.

It must be 30 years ago, since I pulled the chassis from one of those. I'd probably remember the proceedure. :yes:
BTW, looking over the entries on this thread, we haven't heard from Electronic Memory in a long time. He must be taking his College education seriously.
For a young man, he seemed to be well versed. :thmbsp:

Glad you are working on the coffin again.

I am still curious about the tube and how all three filaments would simultaneously open. Perhaps a bad internal weld? My thought was perhaps a bad solder joint at the socket. Did you further investigate this?

I assume you must have ascertained the tube to be bad?

I remember your question about the filaments and will retest to see if I can find out what's what.