A few more historic photos for illustration.
Original C37 & C39 in situ.
Adm 17T12 9003 by
H Boyars, on Flickr
Actual first replacement caps:
Adm 17T12 9002 by
H Boyars, on Flickr
Damaged horizontal size pot:
Adm 17T12 9004 by
H Boyars, on Flickr
Regarding my scenario of destruction of the H-size pot after replacing C37 C39 with 630 volt film caps. The problem with the image on the CRT may have preceded that blunder, and instead of one or both of the 630V caps failing, I could have miswired them