DR-20 HR-1 Reverb amp external effect

[Mastasheo]

I have a HR-1 Reverb amp and the oil spring that I was playing around with on my desk the other day. I was trying to set up some crude connections to see if I could use it as a 1/4 plug in effect for keys/guitar. I could use some help on possible connections that would work. I have connected pins 3 and 4 as my ac power to the amplifier input plug. I would think pins 1 and 6 carry the signal. So I inserted the positive and negative terminals of a cheap ss guitar amp into 1 and 6 on the amp input plug. From there I connected a speaker to pins 1 and 2 of the six pin speaker receptacles plug. So my chain went like so.. guitar- ss amp- Hammond reverb amp- speaker. I also tried the the reverb amp in front of the guitar amp. Sadly no luck past powering the tubes. I do know that I will need to use a resistor to bring the 250ohm down to match the speaker I use and the crystal pickups in the reverb are in working condition. If some of you engineering experts could take a look at the schematic and see if what I’m trying to do it possible without a massive rebuild of the amp. If you could possibly draw up the new connections on the schematic even better! Thanks

http://captain-foldback.com/Hammond_...atics/HR-1.jpg

[muckelroy]

Ok I'll bite. This amp is no desk toy. It requires two field coil speakers - one with a 5k field coil and one with a 250 ohm field coil. Sounds like you're trying to make this work with a single permanent magnet speaker. That won't work. Two PM speakers when correctly wired, with corresponding 250ohm and 5k high wattage resistors could serve. The field coil wires and voice coil wires are separate connections. Don't mix them up. That could be deadly.
This is a confusing schematic - The voice coils attach ground to chassis, which I believe is the top middle lug. Don't use the bottom lug.

Also you have to drive this with a balanced signal. It requires a rather hot signal too so you'd need a strong preamp and an input transformer ahead of pins 1/6. The signal must have a ground reference on pin 2 or weird oscillations will occur.

I have an FR-40 tone cab which uses this and a model H amp in tandem. I love it. But I would never want to separate it from the cabinet itself.

[David Anderson]

I'll just be honest and say that I think trying to use an HR-1 amp as a spring reverb unit is pretty much the definition of attempting to do something in the most difficult way possible.

If you want a standalone tube spring reverb, I might suggest cloning the Fender 6G15 circuit. You can buy a kit and build it yourself.

[Mastasheo]

Yea I do agree that old 1940 wiring is a little over my head but I think it’s fun checking out how that stuff has improved. I will put them back in storage for another 4 years until I find something to do with them. I also have a organ mate reverb unit that needs a new can cap so I will probably continue this project with that unit when I get the time. I received a lot of organ part for cheap a long time ago from my CL so I’m trying to put them to good use without gutting them.