Just found my 7CT1 plugin curve tracer. Used In a large CRT MF like 7603 its great.
Needs a vert PI in the H slot or H PI with X (ext) input.
Only 50V but small and handy compared to the giant 576, 577 and 500 tube tracers.
Finally the TEK test fixtures are rare but very handy, only diff the 577/576 test adapters is they are 5 terminal Kelvin, but still can work on the 7CT1.
Jon
PS: 7CT1 have a pair of axial lytics C30, C32 100 uF that were 25V rated on 30V bus.
A TEK mod later replaced them with 100 uF 50..100V.
Froggie the Gremlin