Un-repairing a scope tube

[tggzzz]

I have a Tek scope tube that is, to the best of my understanding, useless: the grid connection is internally separated, so the brightness cannot be controlled. Could it be used for Other Purposes?

The internal metalwork is quite pretty, and I'm wondering if there is a way to extract it and display it.

So, are there any unpleasant compounds inside a tube? For example, beryllium or mercury.

If none, what's the safest way of breaking the glass and removing the metalwork?

[uncle_bob]

I have a Tek scope tube that is, to the best of my understanding, useless: the grid connection is internally separated, so the brightness cannot be controlled. Could it be used for Other Purposes?

The internal metalwork is quite pretty, and I'm wondering if there is a way to extract it and display it.

So, are there any unpleasant compounds inside a tube? For example, beryllium or mercury.

If none, what's the safest way of breaking the glass and removing the metalwork?

Hi

There are various odd things in there. Opening up one never killed me. Your mileage may vary.

Basic opening process:

1)  there is a glass "nipple" under the center cap on the back socket. First step is to carefully break the nipple. That lets air into the tube. Doing this keeps it from abruptly imploding when you do further work.

2) A glass cutter will take the glass portion off the back end of the assembly. It's a multi pass process (scrape the same place several times) for most of us. For Superman it's a one pass thing.

If you want to cut it further up where the metal shielding is, a disk cutter on a rotary tool might do the trick. There might also be a combo of heat and "pull" that would get the shield off the glass. If so I've never seen it done.

Bob

[AF6LJ]

Don't forget to wear safety glasses.

[T3sl4co1l]

The getter is usually barium metal, a very thin layer so not really much of a hazard.  The cathode coating contains barium oxide, again not very much.  If you like, secure dust by washing them with water, and discard them in a sealed bag.

Most of the structure in those tubes, I think, is glass (possibly borosilicate for low TCE?) and either nickel metal or stainless.  (Nickel is traditional, as well as iron, copper, molybdenum, tungsten and so on for various parts, but I recall Tek used stainless, probably 316, in a lot of their tubes, for whatever reason.)

Tim

[SAUL BRITTO]

I have two tek tubes waiting for any usefull thing too.

[anachrocomputer]

I took some photos of this CRT the other day. They're on Flickr, here: https://www.flickr.com/photos/anachrocomputer/albums/72157662907836404

[T3sl4co1l]

You missed the sexiest part!



Tim

[DenzilPenberthy]

Pro tip for cutting glass tube that I learned from our glassblower at work: No need to score all the way around the tube, just score about 10mm around the tube then wet the scratch with water (I can't remember why this helps).  Heat a glass rod in a flame until there is a nice ball of red hot glass on the end. Then press the ball of molten glass onto the score mark on the tube and it should break cleanly all the way round the tube.

See option 3 here:
http://www.ilpi.com/glassblowing/tutorial_cutting.html

[MrSlack]

So much cooler than an LCD module

[tggzzz]

Pro tip for cutting glass tube that I learned from our glassblower at work: No need to score all the way around the tube, just score about 10mm around the tube then wet the scratch with water (I can't remember why this helps).  Heat a glass rod in a flame until there is a nice ball of red hot glass on the end. Then press the ball of molten glass onto the score mark on the tube and it should break cleanly all the way round the tube.

See option 3 here:
http://www.ilpi.com/glassblowing/tutorial_cutting.html

I was having a chat today with someone who maintained all the equipment at a defunct British Steel research lab. He mentioned the nichrome technique mentioned as option #5 in that URL.

Thanks for all the suggestions. They are a definite improvement on the techique I had in mind: putting the tube in the bottom of a large dustbin, getting a pole with a nail in the end, placing the nail on the tube - and, while cowering as low down as possible, thumping the top of the pole with a large mallet and seeing what's left behind.

It definitely looks like it will be worth tweaking the nipple to release the vacuum, then having a go at neatly cutting the neck. Since all my previous attempts at cutting glass have failed dismally, I'll probably find a local tradesman to do it.

In the meantime I've got a nice little 350MHz Tek 485 scope to play with and clean

[TurboTom]

If the place of the separated grid connection is visible and not obstructed by too much glass artwork,  and the gap that separates the metal parts that should be fused together is rather small, I would attempt to laser weld the two pieces back together right through the glass envelope. This might or might not work but it would be an interesting experiment. If you know someone with a laser welder it would be a job of one minute. Just for curiosity's sake I may try it with a cheap radio/TV amplifier tube. The best about it is that you don't need inert gas 😁

Cheers,
Thomas

[tggzzz]

If the place of the separated grid connection is visible and not obstructed by too much glass artwork,  and the gap that separates the metal parts that should be fused together is rather small, I would attempt to laser weld the two pieces back together right through the glass envelope. This might or might not work but it would be an interesting experiment. If you know someone with a laser welder it would be a job of one minute. Just for curiosity's sake I may try it with a cheap radio/TV amplifier tube. The best about it is that you don't need inert gas 😁

Cheers,
Thomas

Nice idea, but the gap is about 1mm; I don't understand how such a short piece of soft wire became so stressed that  it moved so much!

[gadget73]

Which Tek tube is it?  For some reason I happen to have what I presume to be a perfectly fine 154-0363-00 3" round Tek CRT here.  Yours for the shipping if its useful.  I have a CRT tester, so I can check it before bothering to pack the thing.  I haven't a clue where it came from to be honest, probably came in a box load of junk.

[gadget73]

well, so much for the testing.  Just checked my CRT checker and it doesn't have an adapter to even connect to this, let alone give me any clue about test settings.  I've never used it either, it was also a donated piece of test gear that I've not had reason to use.  I've rebuilt exactly two tube TV sets and have no plans to do more. 

[tggzzz]

Which Tek tube is it?  For some reason I happen to have what I presume to be a perfectly fine 154-0363-00 3" round Tek CRT here.  Yours for the shipping if its useful.  I have a CRT tester, so I can check it before bothering to pack the thing.  I haven't a clue where it came from to be honest, probably came in a box load of junk.

It was a 154-0731.

Thanks, but I've picked up a 154-0676 CRT locally. Now I need to find a source of two broken knobs (vert position and x-position) - which are commercially unobtanium. If I can't find a donor scope, I may resort to 3D printing them in sintered nylon.

Yes, I know I'm spending far too much time and money on it - but I don't care.

[tautech]

What model is your Tek?

[tggzzz]

What model is your Tek?

A 465.

The grey plastic parts of the 366-1426-00 (Y channel V/div sensitivity) and 366-1280-00 (coarse x-position) knobs are broken. Of course, if someone also has functional x-position pots, I'd be interested, but their mis-design makes it unlikely I'll find one.

And - very worringly - I also picked up an almost-functional 485 from the same source

I would be most grateful if someone could enlighten me as to why I need 3 scopes (4 if you include an Analog Discovery).

[tautech]

I would be most grateful if someone could enlighten me as to why I need 3 scopes (4 if you include an Analog Discovery).

You've only got 4?   
 

[tggzzz]

I would be most grateful if someone could enlighten me as to why I need 3 scopes (4 if you include an Analog Discovery).

You've only got 4?   
 

You must understand that my house is full. That's a great way to save money, because I know that if I buy something then I have to throw something out - and I'm constitutionally incapable of doing that. What's worrying me is that my normal rationality is being destroyed by these damned scopes.

[tautech]

I would be most grateful if someone could enlighten me as to why I need 3 scopes (4 if you include an Analog Discovery).

You've only got 4?   
 

You must understand that my house is full. That's a great way to save money, because I know that if I buy something then I have to throw something out - and I'm constitutionally incapable of doing that. What's worrying me is that my normal rationality is being destroyed by these damned scopes.

Careful, it's a permanent affliction you know. 

[Stonent]

Don't forget to wear safety glasses.

And if you have any small particles of glass, make sure to use a face mast, or at least filter it through a cigarette.

[Cubdriver]

I would be most grateful if someone could enlighten me as to why I need 3 scopes (4 if you include an Analog Discovery).

No, you have 3 or 4 scopes.  You need 16 or 17 more to get to the requisite 20 that eevbloggers are supposed to have.   

-Pat