Quote:
Originally Posted by N2IXK
I knew a guy who had a TM-21, but he parted it out for the transformers and other parts for his tube audio hobby. 
The unit he had used a glass CRT. I assume it was a 21CYP22, because it had 2 anode connection buttons on it. |
All the documentation I can find shows that the TM-21 was first built with 21AXP22As, then the second run was built with the 21CYP22A, the third run built with 21FBP22s, and finally the fourth run was built with 21FJP22s.
In theory, you should be able to take a fourth run monitor (like the one I'm buying), swap out the anode lead, add a piece of external safety glass, and pop in a 21CYP22A or 21FBP22. I intend to do so.