Hammond JR-20

[Robert Kazee]

Picked up a Hammond JR-20 for free. Supposed to work.
I removed the amp to have it gone through. Have to change the power cord and install a 1/4 in input. This thing has a Gigantic reverb unit. Anyone else tried one of these units.

[Rich Hlaves]

I've had just about every Hammond tone cabinet made over the years. One of them was a JR20. You will need a preamp to drive it with a lot of output. The preamp that drove these things in an organ setup was located in the organ and very stout. The unit is a two way cab with the 10" speakers doing the bass and the 12s on top for the treble. It is not an ideal guitar amp but I never tried it for steel.

The tubes that contain the reverb springs need to be filled with oil to properly dampen the reverb. There may be a label inside the cab that explains the level to fill each tube. Do it carefully, it is easy to over fill and a real drag to take out the excess. Use mineral oil, yep that nasty stuff sometimes used as a laxative. You get it at the drug store. I hope you don't have to retube it, that can be expensive.

Here is a link to a page of Hammond schematics. The tone cabs are near the bottom:

http://www.captain-foldback.com/Hammond ... matics.htm

You should get an old tone wheel Hammond to drive that thing! They can be a lot of fun. One of the M3 Hammonds I had ended up with b0b our leader as the owner. I have an RT3 organ, HR40 tone cab and a 147 Leslie in the living room. 80 watts of tone wheels and tubes of that B3 sound. I really like vintage Hammonds & they can be had very reasonably.

[Robert Kazee]

Thanks for the info. I was wondering about the preamp. My friend who is going to go through it has all the tubes it will need. I had never heard of an oil filled reverb. Once I get it back, I'll try it with different speaker combinations. I play Bass more than Steel, so I hope it works for one of them. Thanks again for the link.

[Rich Hlaves]

For bass a Tech 21 Sans-Amp pedal or rack preamp might have enough output for the JR20 if you have either one of those. It would certainly make the JR20 easier to control and give you some EQ.

I use the rack mount in my bass rig. Killer tone tool. Never hooked it up to a Hammond tone cab however.

[Robert Kazee]

I have a Sans-Amp, so I'll give it a try. I had a Tube-Fex but gave it to my cousin a while back. Happens everytime I get rid of something.

[Rich Hlaves]

let me know how is works out. Interesting project.