6v6, 6f6

[gayler]

Can they be interchanged?

[A.C.CHILDRESS]

Can they be interchanged?

Doesn't look like it.
Compare the data sheets and the application data if very different in almost all cases.

[gayler]

Thanks for the reply. I could see voltages are lower, but I didn't know if they would live. Also didn't know if the amp, 5F1, would be damaged.

[tubeswell]

Pin-out's the same. Bias is about the same. Plate voltage might need to be watched but it shouldn't be an issue with a 5F1 if you were idling the plate at about 340 I reckon. The recommended plate dissipation is 4.5W, so just run a slightly higher cathode resistor, and/or zener down the B+ a bit if it redplates.

6F6GT/G @ The National Valve Museum

[Old Tele man]

...6F6 is a 'true' five-element pentode, while the 6V6 is a beam tetrode...which means different plate Eb-Ib "knee" characteristics for sure.