20DP4 and 20CP4 are they interchangable

[walterbeers]

Sounds like either one will work, so now I am looking for one that I can put into the Philco that I'm restoring. Set has been recapped, works ok otherwise, except the CRT went so dark, that one can barely see the picture. Emission is almost zero on the original tube. I got the Sams and ordered and paid $125 for a 21EP4, (which I have now posted for sale), as the Sams listed that as the replacement on the schematic, not realizing that some models used the 20 inch tube. Took out the old tube, found the NOS 21EP4 wouldn't fit. Now, I am in need of the 20DP4 or 20CP4. I thought I could retro-fit the 21 inch tube in it, but it won't fit the face plate, mounting corners would have to be cut out and redone, and then the straps that hold the yoke and magnet assembly are too short. Other words the 21 inch just won't work in it. Thanks everyone for you help. If anyone has one of these tubes that is usable, or would like to trade the your 20 inch tube for my 21 inch, let me know.