Percussion Decay Mod B3

[tonewheel1966]

Somebody that I know of has a knob on their B3 to control the perc decay times, but theirs is a solid state preamp and they do not know how it was done. Do any hardened techs out there know whether this is a case of intercepting a resistor under the perc switches or whether it is a case of moving the trim pot from the preamp which does not sound like a good idea.

[T-200]

I can't call myself a hardened tech but I've studied the B3 percussion circuit for hours to find out the differences between that and the E-300 percussion. There's a 4.7Meg resistor between V6 tube and the cutoff pot in slow setting. In the fast setting the L and N terminals are shorted connecting the 1.5Meg resistor (inside the chassis) in parallel with the 4.7Meg. If the short setting is short enough for you, you can try a 20Meg pot between terminal L and the disconnected wire. In fast position 0Meg resistance is normal fast setting and 14Meg resistance is the same as slow setting. Anything above that is longer than slow. If you want faster percussion you can replace the 1.5Meg resistor inside the chassis with wire and you can use the connected pot to adjust from super fast to super slow.

Jussi

[Sweet Pete]

I'm no 'hardcore tech' either.On my AO28 or AO29 type amps/preamps the resistor is easily accessed.One side is chassis grounded,the other side of the resistor is soldered to terminal P on the amp.
It's right under the cover of the braided shielded cables next to Yellow and Green.Usually has a Black wire on it.
I left my A100 stock,it's a 56K.On M3 types,or M100 types I remove the 56K and solder in a 39K.Helps get the percussion to 'pop' a bit more.Some people substitute a potentiometer in place of the 56K.
I don't need a dial.39K 'fixed' works for me.YMMV

[tonewheel1966]

Thanks for the responses guys. Sorry by hardened techs I meant techs who had been asked to do this kind of stuff back in the day :) I've got a Trek preamp in the organ so this probably means this mod is a non starter for me. I just thought that if the intercepting was done in the switch panel then I'd be home and dry.

Best

Dave

[Wes]

Check with Mike at Trek II, you never know.