disassembled
Well-known member
Hey all I just bought a 2:90 off of fleabay an wondered if just the outer 2 tube sockets could be used for class A operation running at 30 watts? I know some of the older 295 simul amps did this but don't know if they just removed the input going to the tubes or put them in standby. The only thing I would be worried about is not having a load on the primary if i removed the tubes from their sockets. For the Mark II, III and IV schematics the switch for simul and class A just lifts Pin 8 on the inner 2 power tubes. Is this what happens on the 295?
To run EL34's in the 290 it looks like i would just have to ground pin 8. Referencing the 290 and mark IV schem. it looks like the screen resistors are the same values but i don't know if the primary voltages are the same.
When comparing the Mark IV power section to the 290 they are very similar so I could probably do a triode/pentode switch on the 290 if i were ever so inclined.
Anyone ever done this?
Greg
To run EL34's in the 290 it looks like i would just have to ground pin 8. Referencing the 290 and mark IV schem. it looks like the screen resistors are the same values but i don't know if the primary voltages are the same.
When comparing the Mark IV power section to the 290 they are very similar so I could probably do a triode/pentode switch on the 290 if i were ever so inclined.
Anyone ever done this?
Greg
