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cjkpkg 4th December 2010 02:01 PM

powerdrive problems
I have been trying to implement George's powerdrive on my 6sn7/300b amp. I finally got everything wired up last night. I did one channel - gave a listen - and then did the other channel.

Fired everything back up and now neither 300b is idling. There is maybe a volt across the 880ohm cathode resistors.

After reviewing the Tubelab site - I am basically working off the TubelabSE schematic - I notice that there is no cathode resistor for the power tubes. Is this correct?

I am using values exactly specified on the TubelabSE schematic. For the negative rail I am getting -230V and b+ was 390 before this.

The only difference is the MOSFETs I used...I went with IRFBF30PBF.

I double checked everything and not sure where I went wrong. I may put it back to non powerdrive just to make sure I didnt fry the tubes...

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