Has anybody ever used a small neck B&W CRT on a large yoke? I would imagine there would have to be a spacer added so it would be stable.

Experimented with that once and it way overscanned, used tissue paper tubes to sorta locate it in the middle

Yes it can be done, but not very well.
I used a 8YP4. Test Picture Tube to restore my FADA 895, (RCA 630TC) clone, it worked well enough for repair till I changed to the 12LP4.

Think my mistake was using a 110 degree yoke on a 12CNP4... was in the 5th grade at the time.

Generally when you use an old narrow deflection TV with a newer wide deflection test CRT you will end up with cropped underscan...The yoke won't be able to bend the beam to the edges and neck shadow will crop it down to a ~5" circle in the center of the CRT.
Doing it the other way around 40s test tube in a 60s fat neck set will have obscene overscan.
Either way it's fine for assessing signal chain and sync function and finding gross sweep issues, but it may hide more subtle sweep problems until switching back to the correct stuff.

Don't remember all the details other than they were both panasonic sets that looked the same. Spliced the CRT wires to the small socket, got the S#!* shocked out of me from the anode cap and tried to center the yoke with some tissue paper tubes & masking tape... this was around 1980

Thanks guys. The reason I asked is that I found a B&K1077 on Ebay but it has no CRT. So I think I can get it for $5 (plus shipping).
https://www.ebay.com/itm/186465495093?_skw=bk1077&itmmeta=01JMN4GK3M3B0E18A9XA3CYFBC&hash=item2b6a35a835:g:lj4AAOSwGMhmV13T&itmprp=enc%3AAQAKAAAA4FkggFvd1GGDu0w3yXCmi1c8q1kaF nOG22%2BCA5DiWI4lTifel8k5xGt%2FZQPZIcvroxdLMiUbC6N mm%2FhVX6sOArviOlzp%2BABmLX8gOEkYr93vEU3fy1exq7pI7 DlfkJQmKJDrngwFL3eXLbuIY6b9urWDo20AGgSw557gl6Loe3E nm6nSYBNQw1X1ShfFqZHWm%2FppTnfigd%2Ff8k9zCtf53vljo QLpnlcO57qHZn%2Br8Xz6KXjdx9vwp9wULn6AWsgBUklY9gN4H nEu2KBhqXljgf872fVbrfcl5C%2BP2mOciqo9%7Ctkp%3ABFBM-LLCpKVl
Here's where I come in. I have an unknown tube that I think will work. Its a Motorola tube that I think is a flying spot scanner tube. I connected it up once and it glowed purple. I think its either military or medical. Has an attached HV lead.

I have an identical Motorola tube (no clue what it's from) base, neck diameter and screen size are wrong for the B&K...You might be able to make it work, but I wouldn't expect great results.

I think the deflection angle is the same- 90 degrees. The neck diameter is smaller so it would need the toilet tissue tube spacers. I can make some smaller slides. I've got a Pomona adapter to adapt the base.

Yeah, I've tried it before. You definitely need some kind of spacer or shim to keep it stable, especially with the larger yoke. Without it, the neck can wobble or be misaligned, which messes with the picture. Just make sure whatever you use to secure it doesn't interfere with the electrical connections or airflow around the tube.

Here's where I come in. I have an unknown tube that I think will work. Its a Motorola tube that I think is a flying spot scanner tube. I connected it up once and it glowed purple. I think its either military or medical. Has an attached HV lead.

What is the face diameter of this tube?

3.5 ".
There is one on ebay:
https://www.ebay.com/itm/163028247398?_skw=motorola+crt&itmmeta=01JMSEFHRPRQZQMWFHVKTCWA7D&hash=item25f53da366:g:0JUAAOSwZMZa6TpI&itmprp=enc%3AAQAKAAAA8FkggFvd1GGDu0w3yXCmi1cznCn8c D5X2G0pD%2FvTfwWoe8YiXvNAiFA2LtVRS8iaZNOJ7mqDC7juJ HahqUNqIoV9myjSBjCy1Inf53xuaIQexoaPWukIceJW148T2Ab 5axCU%2BbkZuYYvV1xZfsp3BoyGsuTqhhjhZ0LV%2FTuJ1TfI6 XidHk81%2FTFkoB%2B%2BsvBUYbwalN9hG1fcS6G0q1fQJzfrR eBN6DYmOVIEB7D9yYx0nqAsngEqzjcZgPja6gLfSWiLZEv31mP 0IQMDCVv0HqAsMBAg%2F4QNeTSnCVS6I33X9Pdr8Gk1UWPXSmp HuuBt1w%3D%3D%7Ctkp%3ABk9SR8Kcvq6mZQ

It is likely a flying spot tube from the ill-fated EVR Player. Motorola developed a fine-grain phosphor for it ca. 1970-1972.
It amazes me that any still exist.

http://www.bretl.com/EVRdocuments.htm

That brings back memories. I acquired several EVR players when they were being sold off for next to nothing. I made quite a good monochrome flying spot slide scanner.

I just remembered - the EVR tube was magnetically focused, and also used beam alignment magnets. This was done to get an extremely fine, but still bright, spot.
So if this is an EVR tube, I'm afraid it won't work without those parts/circuits.

A look inside:
https://www.labguysworld.com/MotoTelePlayer_016.jpg

https://live.staticflickr.com/65535/54349059634_3eace280f0_o.png

The more I think about it, that green coil labeled with question marks may have been a random vertical centering offset in still mode so that a sharp-edged rectangle didn't get burned into the phosphor. Wish I could remember for sure.

I have never seen one of these. Was it color? Seems to be similar to the Rank Cintel.
https://en.wikipedia.org/wiki/Cintel.
That's a high end film transfer machine usually found at production houses.
I think the hard part would be coming up with a focus coil. But I don't think the guy will sell me the 1077 for $5 anyway.

The flying spot tube was violet/UV. The film was two-track black and white microfilm, mastered with an electron beam recorder. Both tracks could be 25 minute black and white, or for color one track was luminance and the other was the color subcarrier and a pilot signal, recorded as sinusoidal density stripes, and decoded back to NTSC or PAL subcarrier in the player.

The luminance resolution was equal to or superior to broadcast; the chroma subcarrier bandwidth was +/- 600 kHz on a 1.8 MHz subcarrier. The pilot was 900 kHz. Frequency and phase variations of the chroma and pilot due to scanning width and non-linearity were cancelled out by comparing the chroma to the pilot.

EVR was an interesting idea that ultimately led nowhere. I wonder where the market was? I've heard they were used on cargo ships and oil tankers to provide entertainment for the crew.

A major problem was that the training/educational/private advertising markets for it could not support the required economies of scale. William Paley at CBS kept waffling about whether it should be mass marketed for home entertainment or if that would dilute CBS's intellectual property too much. He came down on the wrong side of that, and prerecorded VCR tapes for home entertainment ate EVR's lunch.

That was combined with a film duplicating plant that never worked right; the inventor, Goldmark, complained that they had done everything wrong at every step of setting up the plant. Motorola at the end backed out of their contract, blaming CBS for failing to supply usable quality film cartridges; but it was also clear that with the restricted market it would always lose money.

Some promotion continued in Europe for a while, but again, it was too little, too late.

Connected it up to an old Conrac SNA chassis and here's what I got. It sorta works.