Hammond M-3

So, after keeping an eye out for several years for a Hammond spinet, I finally landed one, and on further reading, it looks like I got pretty much the ideal one for my needs. photo of Hammond M-3 organ in our dining room

One of the major requirements was that it fit the organ trailer. It will do this, perhaps even just by gently squeezing the front legs together. If not, I'll need to remove one, or if I'm lucky just tuck it just inside a wheel well.

What I ended up with is a Hammond M-3. It is serial number 143465 with an aftermarket "Organ Mate" reverb unit by Electro Tone Corp. It was originally purchased on July 28th, 1960 in Renfrew, Ontario, Canada. It was delivered with the original warranty card in the bench and the oiling chart on the bottom of the inside of the bench untouched.

So far, I've had to resolder a broken tone generator wire for frequency number 27, D below middle C. It may have broken in transit. I also found a broken drawbar resistor on the upper manual fundamental drawbar. Other than that, it is working great.

I've also gone ahead and done the Poor Man's Foldback (video) mod to this organ to give the high end of the upper manual a bit more brilliance in the upper octave and a half. Here's the before and after wiring and testers.

I'm also interested in the full foldback mod (photos) and Lower manual bass enhancement mod.

2010-10-15: Recapped the ElectroTone Corp. OrganMate spring Reverb amp with a 40/40/20/20uF 500V multi-section cap.

2010-10-16: Recapped AO-29-7 K pre/power amp with power supply recap kit.

Next up is a fluttering D# above middle C tonewheel...

2010-12-09: Acquired beat up Leslie 145. No amplifier, not original treble and bass drivers. I've wired the output of the M3 power amplifier to the Leslie crossover input directly. Treble driver is Electro-Voice 1823 110W 8 ohm. Bass driver is marked Yamaha JA-38020 (may be a Electro-Voice EVM 15B), 8ohm, 120W, 762212, which might be referred to as JA-3802 or JA-3802(0). I'll need to check the crossover which is probably stock, and change it to C=12.4uF and L=3.18mH (assuming 8 ohms for each driver and 800Hz crossover point). (I don't understand why a stock Leslie crossover has values of Lh=3.2mH, Ch=7.8uF, Ll=5.2mH, Cl=12.5uF when I calculate C=6.22uF and L=6.37mH for Likwitz-Riley, C=8.79uF and L=4.5mH for Butterworth and C=7.13uF and L=5.51mH for Bessel.) I also need to port it, since the back panel is a cut down 147 panel on a 145, which eliminated the port.

2011-05-15: I'm acquiring a 20W Leslie 125 amplifier which expects an 8 ohm load anyways. I'll attempt to restore the original circuitry of the pre-amp pedal too.

2012?: I've restored the Leslie Combo Preamp (mark I) to original working order, replacing a blown transistor and resistor and reconnecting the preamplifier circuit board. The microphone-accident-waiting-to-happen 3-pin XLR female receptacle carrying 120V to the motors has been replaced with a 6W connector.

2012-10-09: Received a pair of "Left Hand Bass Kit v2.0" PCBs from Geoff Williamson to lower the lower manual by an octave. I need to order parts to populate them. (* * * * *)

Here's a great set of photos of the M3 tonewheel generator. And here's the wiring of the M3 keys.

Some links I found interesting.

(C) 2010 Richard Guy Briggs Web Page last updated by Richard Guy Briggs Fri Dec 20 15:51:15 EST 2019