[MrFixr55]

A 7C5 would work in place of a 7B5 but not exactly well. The pin diagram is the same, but the grid bias voltage and output transformer impedance would be different. the filament current of the 6C5 is only slightly higher There will be sound but possibly distorted. The 7B5 is the equivalent of a 6K6. The 7C5 is the equivalent of 6V6. You could likely use the 6C5 for now for testing purposes.

I cannot find statistics for the 6B5 for a plate voltage of 180V as used in this set, but here are the stats for both tubes at 250V and the 6C5 at 180V:

_____________6B5 (6K6)________________6C5 (6V6)_______6C5 (6V6) at 180V
Filament current____0.40A________________0.45A _________0.45A
Grid Bias Voltage___-18V_________________-12.5__________-8.5
Max Grid Voltage___18V__________________12.5___________8.5
Load resistance____7600 Ohm_____________5500 Ohm_____ 5500 Ohm
Max Sig Power Out_3.4W_________________4.5W___________2W

UPDATE!!! I found the specs for the 7B5 (6K6) at 180V plate voltage, so the following is the comparison between the 7B5 and 5C5 at 180V. Certainly, they are different tubes which is why the GE Tube Substitution Manual recommended a 6K6:


_________________6B5 (6K6) at 180 V_____6C5 (6V6) at 180V
Filament current____0.40A________________0.45A
Grid Bias Voltage___-14.5V________________-8.5v
Max Grid Voltage___14.5V_________________8.5
Load resistance____9000 Ohm_____________5500 Ohm
Max Sig Power Out_1.5W_________________2.0W