Vibrolux Reverb with 680Ω in Reverb Driver Cathode

[Helmholtz]

I have a Blackface Silverface Vibrolux Reverb from about 1981..

Sounds confusing (?).

[patlaw]

Sounds confusing (?).

It sure was for me for a long time. For a period, Fender sold Blackface VRs (and other amps, I assume) with Silverface guts.

[g1]

And that may be totally true. However, the impression I got from some of his comments is that the "problem" with the 680Ω resistor is well known. Since the versions of this amp before and after this version had the 2.2K resistor, I'd be inclined to "update" the circuit if I were working on one.

I think the idea is that the 680R runs the tube too hot. This can cause the tube to short, which in turn will burn the resistor.