[HAM] HR-40 spring reverb unit advice?

[Ed Greany]

Robert,
   
  Sorry. I searched for my misplaced documentation on the HP450a from years ago. I can't locate it. I recently moved into a new home and have boxes of stuff never unpacked yet. Some day.
   
  good luck.
   
  Ed

Robert H <rch427 at yahoo.com> wrote:
  Hello -- my first post here, so I'll throw in a brief introduction. I'm not an organist, and I don't own a Hammond tonewheel organ (auspicious start, eh?). If it counts, I have a Solovox that I'm restoring, but I'll have to leave the questions relating to that for another time. I'm primarily an experimenter, and I'm putting together a sort of giant modular synthesizer made up of about 20 pieces of old tube-powered bench gear -- sine/square generators, random noise generators, oscillators, etc. One element of this device (which takes up 5 shelves of a custom-made 4 by 5-foot rack) is a Hammond HR-40 spring reverb unit -- the early column-shaped type with the oil-filled tubes. I picked it up on eBay and need to convince it to work with the rest of the system, hence these questions:

1. I've been able to find the schematic on-line for the HR-40 tone cabinet, but they don't seem to address the detached spring reverb unit. I understand that the HR-40 puts out 40 watts peak, but I don't know how much power is actually diverted to the reverb unit, nor what power level below 40 watts could still drive the unit. The amp I'm using is a Hewlett-Packard 450A laboratory amp, and damned if I can find the power output specs for it; just that it produces 40dB of gain. I have a few other (more powerful) tube amps I could substitute, if necessary, but I'd rather stick with the HP, since it's actual laboratory gear. I know -- weird project.

2. There's a sliding lock for the springs which moves over to allow them to vibrate, but I have yet to be able to figure out what actuates the slide. Some sort of servo? If so, I presume it's a lower-voltage DC power? Any kind of cheap/dirty way to actuate this, short of just removing the connection from the control arm entirely and sliding it manually?

3. I've read criticisms that the HR-40 tended to produce reverb that sounded like it was produced inside a rain barrel, with negligible effect on the higher frequencies. Anyone know of any way to modify it to produce a better effect? Using a higher viscosity oil in the tubes? 

That's enough for now. Any advice would be appreciated, other than "get rid of it and buy a proper B". 

Thanks -- 

Robert





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