Hammond M3 amp conversion questions

[nateflanigan]

Hi everyone,
I have a Hammond M3 sitting at a friends warehouse apartment, she's moving soon, I have no room for it at my place, it weighs around 300 lbs, so I think it's time for some changes.

I'd like to turn it's built in amp to a stand alone bass amp.  I think it's an A-29 amp, but I want to verify that in person, then I'll post some schematics and pics.  But, if anyone is familiar with these and can help get my wheels spinning, here's a few questions

-What is the input impedance, and how hot a signal is the amp expecting to see?
-I'd like to add a volume control and tone stack, any pointers?
-It's unclear to me what functions of the organ happen in the amp, ie vibrato, chorus, and percussion.  It could be fun to keep these as part of the finished amp but it's no biggie.

Thanks!

[sluckey]

The AO-29 chassis has a lot of stuff on it that you won't need for a guitar amp. I personally would not bother with converting it. I'd just steal the iron and start with a new chassis. Keep in mind that this is a p/p 6V6 amp and probably won't make a good bass amp without mic to pa.

[RicharD]

A Hammond M3 is actually of some value.  You'd probably be miles ahead selling it.  I have done a Hammond amp conversion or 2.  Even though it's loud as an organ amplifier, it's not gonna have enough power for anything beyond a small bass practice amp.  Turning it into a guitar amp isn't that difficult.  The cup style circuit boards are a pain to work on but it's doable.  Bless their souls, Hammond has very good documentation floating around on the web.    

[nateflanigan]

Ah, should have been more specific, the intended use is a practice/recording/home use amp.  I bought it a few years ago for $80 non-working, oiled it up and it's ok.  A re-tube and re-cap is in order and there's some missing tones, being that I can't really keep the organ I don't know if it's worth the investment.  I'm sure I could make back my $80 but I figured the parts might be worth more to me than that.

[6G6]

The M3 is pretty close to the better known B3.
You might sell it intact for some profit.

[snoof]

if you can get it running right, you could make some profit.  there are black wires going to the top of the tone generator, most likely one of those has come unsoldered, it's very common.  I just had this happen to one of my M3's.  that would account for your missing tones. pull out each drawbar (one at a time, only that drawbar) and go through every key.  that'll tell ya which tone it is.  as for converting the a0-29 to a gtr amp, i must disagree w/ Buttery saying that these aren't loud when converted.  I've done 3(using both stock and aftermarket OTs), and they make great 18-20ish watt rock amps!  plenty loud for me anyway(i guess "loud" is subjective).  and yes, those stock cup boards are a PITA.  I've got one that's set up 5879>12ax7>12ax7>6V6's and it's one my favs.

http://www.captain-foldback.com/Hammond_sub/hammond_schematics.htm

[nateflanigan]

there are black wires going to the top of the tone generator, most likely one of those has come unsoldered, it's very common.

Cool, thanks for the tip!  I made a half hearted attempt at mapping the missing tones as you described when I first got it working, but never really followed through. 

Has anyone re-used the speaker? 

[snoof]

they can't really hang IMO.  they will just get shredded.

[nateflanigan]

Wow, out of curiosity what makes you say that?  My thinking was that the built in speakers handle the bass notes from the foot pedals just fine.

hopefully, I can spend some time with it this weekend and try to get acquainted with the circuitry.  Maybe post an ad on craigslist, see if anyone bites.

 

[PRR]

> the built in speakers handle

Organists don't distort. Give them 18W and they play 10W-15W tops.

Give a guitarist a 18W and they play 25 Watts. Roughly double the heat in the voice-coil.

[DummyLoad]

Organists don't distort. Give them 18W and they play 10W-15W tops.

yes, if you play deep purple... 

[6G6]

Organs don't have the sharp attack of a guitar.
While they may have a higher average volume for a given note,
and may seem louder, they don't distort when you pick and
fade out afterward.
That said, many organs use fair quality speakers (at least for the
time period they were made in) and they might hold up in a sealed cab.

[RicharD]

I have found when you have an old speaker which hasn't done much work over the ages and suddenly your demanding guitar duty out of it, the voice coil tends to unravel.  I doubt anyone here would argue a huge percentage of tone comes from the speaker.  A "Vintage" tone may be very much derived from using old speakers, but you gotta be careful.  If you're going to use old speakers, it might be wise to heat them up and cool them down several times before pushing them.  Even the, the lacquer protecting the voice coil may fail.

[nateflanigan]

I spent a little time with the ol' m3 this weekend.  I'm really torn on what to do with it, it really seems like a waste to tear it apart just for the transformers and a few other odds and ends.  There's two for sale on craigslist in my area, one in pristine condition for $300 and one that's closer to mine condition wise for $125.  I've been reading about people chopping them to make it kind of portable, maybe that would make it more attractive to a buyer.  dunno

[snoof]

$100 - $150 is what they go for around my area.  One of mine is chopped, but it was quite a bit of work to do, and it's still heavy, it's just in 2 pieces now.  if you wanna part it out, ebay the drawbars, keys, and ao-29 amp.  that seems to be what people are after.