Tektronix 2215 CRT cracked - options?

[fivesixzero]

Hi friends,

I recently picked up a Tektronix 2215 (non-A) that's in pretty great condition aside from one critical piece - the CRT is broken. Its actually shattered at the neck, basically, so it doesn't look like the glass is at all salvagable.

Over the last few weeks I've scoured the web looking for any source of these parts, either NOS or used, and it doesn't look like there's much hope in finding a replacement part. I even sent an email to the Sphere.co.ca [1] folks to see if they had one, unfortunately struck out there (although they were kind enough to reply quickly to my inquiry, which was nice).

Thanks to the Tekwiki and other sources I've managed to at least find the part number from the service manual [2]. And it looks like the same CRT is used on the 2213 as well, which could be useful knowledge.

Tek part info:

Code: [Select]

154-0838-00
V870
Electron Tube: CRT,T4642-31-2
I'm hoping that there's something I missed in my search, or a gap in my knowledge, that someone here might be able to help with. Or maybe someone out there has a 2213 or 2215 that's otherwise toast with a solid CRT? One can hope. I'd hate to see this thing to to waste just because the CRT's dead.

One far-fetched option I've considered is finding a way to replace the CRT display with something digital via FPGA magic but this looks like it'd be immensely difficult with a fully analog scope like this. This headline[3] on Hackaday gave me some hope but it became quickly apparent while reading that its a fix for a totally different problem, on a scope that already had an LCD.

So what do ya'll think? Any chance for this lovable old 2215 to come back to life?

[1] https://www.sphere.bc.ca/test/tek-crts.html
[2] https://w140.com/tek_2215_service.pdf
[3] https://hackaday.com/2017/06/01/fpga-rescues-scope-from-the-dumpster/

[bdunham7]

There's zero chance you can reasonably adapt an LCD into a non-raster display device, let alone one with deflection rates of 60MHz +.  You may as well build a scope from scratch.

The way you find something like that is by being patient.  Put the scope in a closet, figure out what scopes have the same tube (there may be quite a few) and check eBay and craigslist from time to time.  Eventually you will luck into one. One thing you have to worry about is whether the rest of the scope works or not, so you want to get a CRT as cheaply as possible or get a complete scope with issues to swap it out of.  I find that 22xx scopes that get parted out turn into skeletons pretty quickly.

Also, I believe that the 154-0861-00 CRT will also work in your scope, although I can't be 1000% sure.  This is the CRT used mostly in the 100MHz versions like the 2213A, 2235 and 2235 as well as the hybrid digital versions like the 2221, 2221A, 2230, 2232, etc.  You might check on tekscopes.groups.io or maybe someone here knows for sure.  I have one of these 154-0861-00 CRTs that I kept around for testing and it mostly works except is has an aberration or distortion at one point on the screen due to a small loose part inside.  I'd send it to you for the cost of postage if you want to try it and test the rest of your scope before you spend a lot of time, money or effort on a good replacement. Or, it may work well enough for you.

[james_s]

An analog scope is pretty much a highly specialized CRT, with a few ancillary components bolted around it to make it work. Most of the magic is inside the CRT itself, and obviously that one is toast. I wonder what on earth happened to that thing? I've never seen one broken that bad.

Keep on the lookout for a beat up parts scope. I gave away a 2215 a few years ago that was in mediocre shape but had a mostly decent CRT, I'm sure there are others out there. You could also sell yours as a parts scope, which would allow someone else to restore their beat up one.

[m3vuv]

ive one in good condition from a 453a,would that help?

[fivesixzero]

There's zero chance you can reasonably adapt an LCD into a non-raster display device, let alone one with deflection rates of 60MHz +.  You may as well build a scope from scratch.

Yeah, my thoughts too, especially after doing some more digging.

The way you find something like that is by being patient.  Put the scope in a closet, figure out what scopes have the same tube (there may be quite a few) and check eBay and craigslist from time to time.  Eventually you will luck into one. One thing you have to worry about is whether the rest of the scope works or not, so you want to get a CRT as cheaply as possible or get a complete scope with issues to swap it out of.  I find that 22xx scopes that get parted out turn into skeletons pretty quickly.

That's what I've been preparing myself for, mostly - a long, patient low-key search for parts. I've got some search alerts set up on fleabay for the CRT at least. And I've been keeping my eye out or other 22xx scopes available nearby on Craigslist or in the usual surplus shops.

In the meantime I'm definitely curious about the health of the rest of the hardware on the scope. Its the first analog scope I've torn down for repair so its new territory for me. I don't have an isolation transformer or a differential probe for the bench yet so I'm a bit skittish about working with high voltage stuff coming off mains too. If anyone has suggestions for validating functionality on a "headless" scope like this I'm all ears.

Also, I believe that the 154-0861-00 CRT will also work in your scope, although I can't be 1000% sure.  This is the CRT used mostly in the 100MHz versions like the 2213A, 2235 and 2235 as well as the hybrid digital versions like the 2221, 2221A, 2230, 2232, etc.  You might check on tekscopes.groups.io or maybe someone here knows for sure.  I have one of these 154-0861-00 CRTs that I kept around for testing and it mostly works except is has an aberration or distortion at one point on the screen due to a small loose part inside.  I'd send it to you for the cost of postage if you want to try it and test the rest of your scope before you spend a lot of time, money or effort on a good replacement. Or, it may work well enough for you.

I hadn't considered the idea that other tubes might be functionally compatible. I'll have to dive into tekscopes.groups.io a bit more. I did some heavy searching in their archives trying to find info on this model and its CRT but hadn't gone as far as joining up and asking them some questions.

I wouldn't ask anyone to go to the trouble of sending a CRT without doing a bit more homework and at least doing a basic functionality pass on the scope. Would be a shame to drop in a possible replacement only to have it blow up or something. But I really appreciate the offer. And I might take you up on that in a few days once I've done some more work on this.

[fivesixzero]

An analog scope is pretty much a highly specialized CRT, with a few ancillary components bolted around it to make it work. Most of the magic is inside the CRT itself, and obviously that one is toast. I wonder what on earth happened to that thing? I've never seen one broken that bad.

While talking to the surplus shop staff it sounded like this might've been on a pallate that took a pretty heavy hit while moving around the warehouse. Since this guy wasn't on the edge that took the impact it didn't have any obvious cosmetic damage but I'm guessing that a heavy enough kinetic jolt could expand an existing hairline crack or something.

Given that this is Minnesota, I also don't rule out the idea that the CRT could've been exposed to unusually large thermal gradients as well, particularly if it was stored outside in winter since it can get down to -30c on a bad day. I can just imagine a pallate sitting on a truck overnight being pulled into a warehouse that's at +10-20c... Not the kind of environment precison CRTs thrive in. Epecially if surplus shop staff decided to try and power it on while it was still cold.

Adding to that, I do recall seeing that some of these scopes had to have a Tek service modification [1] done that reduced its voltage down to "factory center 6.3v". Based on a quick read of the doc it sounds like this SN is within the range of affected units. Taking a closer look at my pics of the PSU area it indeed doesn't look like this was done based on two things: first, I think they're supposed to modify the P/N of the transformer with a "-01" to replace the "-00" and, second, it doesn't look like the heater voltage winding was modified.

[1] http://www.hakanh.com/dl/docs/hardtofind/SUP3010.pdf

Although the service doc mentions that this could "affect the lifetime of the CRT", its easy for me to speculate that the urgency they recommend up front might be related to actual streseses on the glass itself. But I'm a relatively uninformed researcher so far so that's just speculation.

Keep on the lookout for a beat up parts scope. I gave away a 2215 a few years ago that was in mediocre shape but had a mostly decent CRT, I'm sure there are others out there. You could also sell yours as a parts scope, which would allow someone else to restore their beat up one.

For now I'm hoping to find a parts 2215 that I can use for this guy. I'd hate to take another almost-functional 2215 out of circulation just to get this one working, but if I can find one with a dead PSU/front-end that's beyond repair that'd be ideal. Its hard to know looking at stuff on fleabay though since it seems like most parts-only 2213/2215 models seem to go for $100+ after shipping, which is a lot to risk for a device that might also have a bad CRT. 

[fivesixzero]

ive one in good condition from a 453a,would that help?

Unfortunately I don't think that'd help with this unit, given the pretty large difference in designs. But I really appreciate the offer.

[fivesixzero]

Also, I believe that the 154-0861-00 CRT will also work in your scope, although I can't be 1000% sure.

I did some research on this and it looks like this tube has a similar rear connection profile but based on some photos I found online it looks like it lacks some pins that are partway up the tube, right around where mine cracked. I'm not sure what those pins are for yet (need to spend more time with the service manual) but it looks like they could be important.

I may have lead on a proper parts scope at least. If that works out it'll be in my hands late next week or early the week after. I'll keep this thread updated with any progress or questions.

[bdunham7]

The mid-section pins are the horizontal and vertical deflection plate connections and they will certainly be present on both varieties.  Those connections can be difficult to access and need to be handled with extreme care because putting stress on those pins can damage the CRT internally, or I suppose if you really are rough you could break the tube in half. 

[fivesixzero]

The mid-section pins are the horizontal and vertical deflection plate connections and they will certainly be present on both varieties.

Ahh, I see. Thank you for the info. The photos I was looking at of the 154-0861-00 were pretty crappy so the pins probably just blended into the pixelated mess.

[woodchips]

Looks like a standard 10x8cm side contact CRT. There are probably dozens that will fit and work.

They are not particularly fussy about voltages, only if it has the advanced flood guns to raise the writing rate.

They are only held at the screen and base, so provided it isn't longer then it will fit.

Some CRTs from the video test gear have side access plates, whilst the screen may look a bit odd it will give you a trace.

Just look for any similar era and cost scope, the tube will probably work, and cost peanuts. I have been scrapping analogue scopes for some years now, no one wants them, no market, so buy now.

[fivesixzero]

Those connections can be difficult to access and need to be handled with extreme care because putting stress on those pins can damage the CRT internally, or I suppose if you really are rough you could break the tube in half.

That might explain what happened to the tube. The connections to those pins were already removed when I opened the case. And when it came time to remove the CRT, I could tell it was already snapped in half - the front of the tube just slid right off.

Just look for any similar era and cost scope, the tube will probably work, and cost peanuts. I have been scrapping analogue scopes for some years now, no one wants them, no market, so buy now.

That's good to know! My knowledge of CRT device repairs is slim, so I'm learning as I go here.

It looks like tubes from similar models occasionally pop up here and there for $20-50 so if there's a chance other tubes would work it sounds like a path worth pursuing.

[highpower]

Adding to that, I do recall seeing that some of these scopes had to have a Tek service modification [1] done that reduced its voltage down to "factory center 6.3v". Based on a quick read of the doc it sounds like this SN is within the range of affected units. Taking a closer look at my pics of the PSU area it indeed doesn't look like this was done based on two things: first, I think they're supposed to modify the P/N of the transformer with a "-01" to replace the "-00" and, second, it doesn't look like the heater voltage winding was modified.

I'm glad you mentioned that. I've have one of mine torn down for quite awhile now and haven't had the opportunity to put it back together yet. I need to remember to do that mod. Kind of forgot about it. 

[amyk]

This guy on YouTube is the only person I know of who might be able to repair a CRT like that: https://www.youtube.com/user/glasslinger/videos

[Gyro]

Unfortunately the cathode emissive coating will have been ruined by the loss of vacuum, it would need an electron gun rebuild.

You could mount it as an attractive ornament / talking point - forum member tggzzz has one just like it.  Somebody else has already done most of the work for you too!

https://entertaininghacks.wordpress.com/2016/03/09/rescuing-a-broken-tektronix-465-crt/

[wn1fju]

I feel your pain!

I picked up a Tek 475 for $40 a couple of weeks ago, sold as "doesn't power up."  I figured it was likely to be a power supply problem due to one or more shorted tantalum caps, as the Tek 400 series of that vintage are well known for that problem.

But when received, it did power up just fine after exercising the power switch a few times.  But the CRT showed no trace, so I pulled the back cover and took a look at the CRT.  See the picture.

[fivesixzero]

I'm glad you mentioned that. I've have one of mine torn down for quite awhile now and haven't had the opportunity to put it back together yet. I need to remember to do that mod. Kind of forgot about it. 

Yeah, it looks pretty important based on the wording in their service manual. I'm not sure if the recutction in "the lifetime of the CRT" refers to phosphors, electron source, the glass itself, or something else. Either way it's a pretty quick fix.

This guy on YouTube is the only person I know of who might be able to repair a CRT like that: https://www.youtube.com/user/glasslinger/videos

Really interesting videos! Thanks for sharing that. Pretty sure its not fixable tho, even by a glass master, given that there's definitely no vacuum left and (like Gyro mentioned) the emissive coting is probably 100% toast from being exposed to the air.

You could mount it as an attractive ornament / talking point - forum member tggzzz has one just like it.  Somebody else has already done most of the work for you too!

I've definitely got a few creative ideas in mind for making the super cool electron gun mechanism into a display piece. Its super cool looking on its own!

But when received, it did power up just fine after exercising the power switch a few times.  But the CRT showed no trace, so I pulled the back cover and took a look at the CRT.  See the picture.

Ooooof. Yeah. Its definitely painful to have an otherwise functional device on your bench that just can't be made to work thanks to some unobtainable broken part. And a broken CRT on an analog scope is probably the least replacable part on the whole damn thing. 

[jdragoset]

May be a wild shot but 154-0861-00 is direct pin-for-pin as comes in the Tek 2235, which are quite common showing the CRT functional with other problems.
Dave H. and James S., please advise.

[james_s]

Yeah, it looks pretty important based on the wording in their service manual. I'm not sure if the recutction in "the lifetime of the CRT" refers to phosphors, electron source, the glass itself, or something else. Either way it's a pretty quick fix.

It's the electron source. Run the heater too hot and it boils off all the emissive oxides. It can burn out the filament too but mostly it just kills the cathode. The result is a tube that acts like it has a lot more hours on it than it does and gets dim and fuzzy.

[james_s]

May be a wild shot but 154-0861-00 is direct pin-for-pin as comes in the Tek 2235, which are quite common showing the CRT functional with other problems.
Dave H. and James S., please advise.

Sorry I have no clue, I suspect it will work since the 2235 is in the same family as the 2215 but I don't know what tubes cross to what scopes.