Can I remove power amp tubes

[denitronik]

Is there any harm in removing the power amp tubes if your not using it (no speaker connected).
A friend has bought a Hammond M3 organ and he cut the cabinet to remove the bass pedal board and the speaker. He just wants to use the preamp section into his leslie. I suggested he removed the two 6V6 tubes, is this correct?

thanks!

[Albert Kreuzer]

No harm to the amp, but you're interrupting the NFB from the OT secondary to the preamp. Not sure how this affects the sound.
You could replace the speaker with a dummy load 8 Ohms/20W.
If it's an early M3 with the field coil speaker, replace the field coil with a 700 Ohms/20W resistor (better 30W).

Cheers,
Albert

[denitronik]

Thank you for the response!
It is an early M3 and I wasn't sure what to do about the field coil, now I know!
I'm aware about the NFB cut but it doesn't worry me.

[g1]

It would also be a good idea to check the heater voltage and the B+ with the 6V6's installed, then with them removed.
The B+ may rise and strain the filter caps depending on their working voltage (esp. with modern AC line being higher than when the amp was built).
An increase in heater voltage may decrease the life span of the preamp tubes if too high but this probably won't be a big issue.