Tube Amp Archive

I have an allen hot fudge w nuts, which is a 6G3 circuit. I've also had a 5E3. Tonally, they have lots of similarities. The 6G3 has a much tighter bottom and is quite a bit louder! Fixed bias, instead of cathode bias with the long tail phase inverter (like the blackface DR). Also the preamp section ...

That makes sense. Thanks again, Martin!

I have it working again, heatsink seems to be doing its job. One last question- I noticed the pad on the mosfet reads the full B+ voltage (430v) regardless where the VVR dial is set. Is this normal? I was under the assumption that the pad would read the remainding voltage that was discarded from the...

Will be replacing the diode and using non conductive thermal compound. But I'm a little confused on where to put the heatsink and what kind to get. Can I get one from any computer store? Does it go under the mosfet or the other side of the chassis? Or just as close as I can get it? Btw, thanks for a...

I did just read a post from Dana himself stating that he recommends a heat sink if using a steel chassis but not so with an aluminum chassis. Mine is steel.

I also plan to use thermal compound once I get the replacement mosfet. should I be looking into a heat sink as well?

No heat sink, just the insulator (which is what Dana recommends)

Those are 'before' pics. The mosfet is insulated and installed on the back wall of the chassis. It worked fine for a bit, I moved the amp across town (without a head case) and it wasn't working next time i fired it up.

Well, it didn't last long. The B+ out is now reading 345v at its lowest pot setting and the chassis is no longer warm where the mosfet is. I'm assuming MOSFET stopped working?

Boom! Got it! I had the choke before the VVR. It's working great, now!

Thanks a bunch, Martin!

ok, I think I've got it working right. I broke the connection going from the standby switch to the OT/plates. I tested it according to the instructions I found online. Can someone at least confirm that my measurements are where they need to be? Also, I replaced 2 resistors on the VVR board from 100K...

I'm installing a (fixed bias) VVR3 board from hallamplification on a Allen Hot Fudge (6G3 Brownface deluxe clone). After reading instructions, I'm still a little confused as to where to insert the VVR. There is a red wire connecting directly from the standby switch to the first large filter cap. I'm...