Benson 300H

[sixstringer]

I've got a Benson 300 (serial # 37) on the bench. All original caps, tubes, the works. Ron Benson replaced the old 2 wire AC cord with a new 3 wire version a couple of years ago and added a new reverb tank but left the rest of the amp alone. The owner want's to keep it "as is" (he was friends with Howard Roberts and Ron Benson back in the day) but is asking if the reverb and tremolo could be made a little stronger. Both effects are pretty anemic.
I'm thinking of changing the reverb controls to linear pots as a start. Does anyone have a schematic for this amp? I've heard that it's a modded Gibson GA-50, but it does not look very close to me. I found a power amp section schematic online that looks correct but no luck finding a preamp schematic. Any help is most appreciated.

[Leo_Gnardo]

I'm thinking of changing the reverb controls to linear pots as a start.

I don't see what's the advantage.

If you get a good reverb sound at some number or % of turn then that's where the sweet spot is. So what if it's not like many typical amps (Fender for instance) where dialing reverb to 3 is too much. Personally I like having a range of control spread over a large part of the pot's turn.

If there's really something wrong with the circuitry and you barely have reverb with the control dialed way up, there's a problem to be solved and it isn't the pot's taper.

[Stevem]

Does the amp use octal preamp tubes like a 50, or 9 pins like a 50T model?
Is the reverb pan plugged in right, try swapping the two cables on it, also the pan may not be the right one impedance wise.
All too many old pans and even new ones have the transducer coils that ride on the iron core very loose which makes for muddy verb and less verb than the amp should have!
If you get some medium super glue and run it down into that core gap to lock on the transducer, then at least the pan will be 100%!
The depth of the tremolo is in direct proportion to the strength of the tube in that circuit and the condition of that circuits resistors and caps, it never pays to trouble shoot those circuits if the tube test good, just shot gun all the plate and cathode resistors and the caps as 5 bucks in parts will spare you 3 hours in repair time!

[Roe]

SChematics:
http://utstat.utoronto.ca/mikevans/hrob ... 0H400H.jpg
http://utstat.utoronto.ca/mikevans/hrob ... 00HPWR.jpg