Need help with 5f2a mod

[Bruce / Mission Amps]

Well I put it together today,staing going thru the step by step start up, everythings going well. Put the tubes in, start measuring voltages,and....POP!! the 25u25v cathode bypass cap on the power tube explodes. I think it was just too much voltage going thru it. Gonna order a new cap,higher voltage this time and see how she works .

Or, you installed it backwards with the positive end grounded.
Check check to be sure.... usually a 25v E-cap here will not simply pop unless connected backwards or the tube is grossly over biased.
Over biased means too much voltage with respect to the grid and cathode, not current.
I always use at least a 50v E-cap in cathode biased power tubes but even a 100v E-cap is not out of range.

[big-daddy-59]

No Bruce I didn't install it backwards, double checked everything before putting power to it. I think that I probably should have put at least a 50v in there, and I think I may have physically damaged it shoving the leads thru a tight eyelet hole. However I think that 470 Ohms for the cathode bias resistor may have that 6L6GC I'm using biased too hot, but I get conflicting advice regarding whether I should use a higher or lower value. I've got a 240 ohm 5 watter that could go in there and I have a 300 ohm on order.

[MWJB]

Do not use a 240ohm or 300ohm cathode resistor with your PT & a stiff recrifier like GZ34...you say you think the 470 has the amp biased too hot, but then you suggest 240ohms or 300ohms which will bias the 6L6 HOTTER still?