[HAM] HR-40 spring reverb unit advice?

[Dave Bishop]

----- Original Message ----- 
From: "Robert H" <rch427 at yahoo.com>
To: <hammond at zeni.net>
Sent: Monday, July 02, 2007 1:25 PM
Subject: [HAM] HR-40 spring reverb unit advice?


> 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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