Hammond AO-29 Guitar Amp Conversion + Make Pickup w/ Unused Parts 

+Tim Stanley In the case of some of these Hammonds, it's just luck. They used good parts and built to last. The credit goes to the engineers at Hammond. I feel like I'm taking a chisel to the electronics equivalent of a Michelangelo sometimes. I'm defacing more than anything.

Hi Ed. Welcome aboard! Thanks for subscribing. And thanks for the glowing review. Sounds like you have a lot of very nice equipment there. I would encourage you to keep at least one good Hammond intact. They really are marvels of electronics engineering. I doubt they will ever be made the same way again, and mark my words, no matter what the market thinks of them today, there WILL come a time when people will value these again. Nothing sounds like a real Hammond.

oh I couldnt agree more- I have the utmost respect for Lauren's Hammond, and the SOUND is just the coolest thing this side of ...well , you name it- i have about 7 M-3's still, and i am going to sell at least 5 of those when i'm done restoring them, all from the 50's and a couple other odd ones, 3 or 4 that actually work fine and are pristine examples, but I have run out of room!!! there is very little that cannot be re-used, speakers, keys, amplifiers and circuits, even the solid state models- the 'expression pedals make great volume pedals- i even use the wood from the cabinets to make attractive housings for the amps- I have 5 or 6 'Leslie' 'cheesewheels' that I am building into guitar cabinets, and the SOUND is just the best- I will post a video later in the week of the one ive completed, it is just addictive.. the ones ive scrapped are from the 60's, and they all have the 'gooey foam problem' which is where Hammond decided to use foam rubber to insulate the key wiring, instead of felt- and the foam melts onto the wires and is very acisic and eats them up, and the wire is SO thin, like a human hair, 3 per key, all bundled in groups, so they really cant be fixed- i have an M-101.with this problem, and it has an awesome vibrato like nothing else, but 5 or 6 notes dont come through...so i am going to try and switch out the key assemblies for an 'L' from the fifties, but I'm not sure if it will work . i have several modern synths that have an OK Drawbar organ patch, but if you hear them side by side it doesnt compare- no way.

Using the wood is a good idea. The cabinetry, baffles, speakers, amps, hardware, WIRE, you name it. Parts galore if you have to scrap one. I've made a couple standalone Leslie cabs out of ones from organs. the cool thing about reusing the cabinetry is you can get creative.

What a great comment, good luck with all your building and playing efforts. The Guitologist is right as well, one day those old Hammonds will be sought after gems people will pay stupid prices for. You just can't beat the sound of the real thing, and once you've heard it there's no going back.

Thanks so much for subbing and joining us. I too am a huge admirer of Uncle Doug. He, Rusty, and Jack are like old friends in my house. I wish you luck on your 29 conversions. I'll help anyway I can.

Here's a dream I have: Uncle Doug performing the same conversion you've done here. I have a feeling we would both benefit. These amps are so easy to get I had to stop doing "organ removals" just because they were clogging up my basement! There's a lot of amp here, I suppose. Somehow using that row of 12AX7s would be nice.

Awesome! Best of luck. Let me know how it comes out.

This is what it's all about for me. Thanks for the comment!

+Aaron Collins Thanks for your comment, Aaron! I had considered also omitting the 6AU6 and just going with the 12ax7 and 12au7 in pre. The AU only uses one of its triodes in my design, so you wouldn't be losing a gain stage doing that. In fact, if I wanted to hot rod this amp further, I could go in and use that triode. I kept all the parts I extracted from the amp. I know I'll be using all kinds of spare parts for a long time.

The tubes alone are easily worth that.

@@TheGuitologist holy shit that guitar! Awesome! Ps : and the trem on that turned out unreal. I can hear “born on the bayou” sounding real good on it. :)

Thanks for the comment! This isn't the first time I've heard from people in Brazil saying this. I think I might need to load up a truck with amps and drive down to Brazil! Might make a fortune.

+joe bartolini the AO-43 is still on my list! Haven't done one of those yet. The beauty of this AO-29 is I can go back and use one of the unused tube sockets to create a reverb circuit if I want, maybe build in a nice-sounding Ampeg or Fender circuit. Got space for a transformer too.

+joe bartolini The PA columns might be awesome. Just check the impedance of the speakers. Some of those PA cabs had, like 32 ohm speakers installed.

i did an ao43 and i made it work with reverb on footswitch, and have a dirty channel that is just heaps of volume and gain. no test gear, no schematic... just experimenting.. thing SLAYS!!!

The chassis is really too long, but it does make a great guitar amp.

​@@TheGuitologist it would be perfect for a head for my 4x12 cabinet

Think twice before stripping it. Play it a while. I've recorded albums with the M3.

I got it running! The tone wheel was a little tight. It sounds great, the amp works! It has the upper foldback already. The drawbars need some cleaning, and the vibrato is out of commision. I need to find a leslie now! I think i might go ahead and pull the amp, and chop the organ down. I love the instrument, and want to preserve it, however in its current form it will end up in a landfill after I'm gone. A nice compact good looking chop, with a solid state pre amp should keep it viable for a few years!

I have a working AO-29 I pulled from an organ. I assume your amp is still inside the organ? I'm just wondering if I power up the amp, with speaker, and plug a guitar into the rca jack that might work the same as your example. Did you use any preamp pedal or just plug a guitar straight in?

@@montag4516 yes you can plug a guitar into rca jack for low volume ... adding a pedal in front will bring up the volume quite a bit ..... there is also a higher level input available under the long side cover, i think its the 3rd or 4rth tab from right then just ground the other side of the input to chassis

If you join my locals community, you'll get not only help from me, but probably from a half dozen other experienced techs who are over there: theguitologist.locals.com

I will make more of these for sure. I have one other one waiting in the wings.

Yep, that's me. I live in Louisville now. Been here going on 4 years. Thanks for the comment!

+arumrunner I have done a sound projector project before. Here it is if you didn't see it. It's a different model: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-cqDm4iRooWU.html

+Mike Haapoja Thanks Mike. Seemed the logical thing to do with that extra 7-pin socket.

Yeah, definitely good for that stuff. And some new speakers would be really good for it.

Pick them up. That would be a GOLD mine here in Australia.

I did not make a layout diagram. There are so many options of where to mount things. I suggest doing what i did...go through the final schematic component by component and earmark the stuff that can stay, then remove everything else with extreme prejudice. Takes a little while, that's kinda why i edited most of that out, it would have been a 2-hour video. When all the extraneous stuff is gone, go back and double check each component that's supposed to be there, checking off each one on the schematic, starting from input and moving trough output. Then start at power plug and check everything off in power supply through the capacitors. Then build out your tremolo circuit. You may also be able to pause the video and get an idea of the layout. You're like the second or third person to email me and ask, so I'll probably take some detailed photos of the end result and that'll help you. In fact, I'll go ahead and do that now and publish them on my Facebook page and link from here when I get them up.

+The Guitologist sweet! Thanks a TON!

facebook.com/guitologist/photos/?tab=album&album_id=912735435518832

If you want to email me a pic I'll get to it when I can.

+The Guitologist -- email sent.

Start at the input of the circuit you WANT to build and begin adding components that aren't there yet. If a component is already there, decide if you want to change its value or keep it. Go through V1, V2, etc. just like that. The power supply is something else.

@@TheGuitologist thank you!

@@TheGuitologist Each 12ax7 seems to have a capacitor coming off of the plate and then a resistor going to ground that you normally don't see in a preamp. Usually it's just a plate resistor that the B+ passes through and a coupling cap. Why the extra cap and resistor? Is it to bleed off highs? Thanks in advance

Word

+Bucyrus Erie12 Thanks!

Yes. Kept old cans.errr wait, maybe not. Can't recall.

@@TheGuitologist Looks like you did have them checked on schematic .... just thought the 50uf were a bit big as the 1482 used 20uf

+Bbendfender There are some books out there you can buy if you'd like to start learning. I can vouch for the following: Design and Construction of Tube Guitar Amplifiers by Robert C. Megantz amzn.to/23pHlRn Designing Tube Preamps for Guitar and Bass, 2nd Edition by Merlin Blencowe amzn.to/1VjEbKF

+The Guitologist Thanks, I may check them out. I'm probably too old to start learning stuff like electronics although I have maintained my old Fender amps for years.

No. Never saw anyone do that.

M Series. M-100, M-1, etc.

@@TheGuitologist Thank you!

Email me a photo and part numbers of what you need. Ill see if I have it. Bradlinzy at gmail

+Barefeet200 Thanks for watching! Be sure to make a video of your build and link me here so I can see how it came out.

+Barefeet200 As for the components installation on the boards, just heat the conical part sticking out the back of your iron until the solder is good and molten, then insert your component using needlenose pliers.

+Robert Landry At 25:00 there is a short discussion of the tone circuit I used and where it goes.

+Robert Landry The signal input is discussed as well. I input the guitar signal into the 6AU6 pentode tube grid.

Thanks! I like the way this one turned out too.

No, didn't feel the need. I just edited the existing schematic crudely. The final schematic is near the end of the video. Good luck on your build! It's a fun one.

Change all power and screen resistors and try it again. Use higher wattage parts where possible and change to metal film where they were formerly carbon.

Thanks, Ill give that a try...its way too nice of an instrument not to restore.

Never seen that exact model, but the later SS organ amps can make good bass amps, Keyboard amps, or clean steel guitar amps, I'd suspect. Pair it with a good speaker and I bet it sounds great in these applications.

can't make a good guitar amp outa it?

Yeah, sure. It would just be very clean and stale probably.

do i need some sort of preamp? you know those were made right over in madison in.?

Did not know that. I'm assuming you'll want some kind of effects boost or multi-effects pedal to use with that.

Why?

Reverb could be added to the design. You'd need at least one more tube in circuit, a tank, etc. As for the schematic. It's all in the vid. Toward the end. Your best bet is to print a regular schematic and make the changes I outline on your schematic. Good luck!

Probably. If it's an amplifier, it can be made to amplify whatever you need it to.

+ThaLegendaryNoob great question! First, it would not hurt you to buy a couple books. Here are the ones I recommend: Designing Tube Preamps for Guitar and Bass: amzn.to/1VeydtP Design and Construction of Tube Guitar Amplifiers: amzn.to/1VeymNK If you have no background at all in working with electronics, you should see if your local trade schools or community colleges offer some kind of practical electronics classes. If you already can use a soldering iron and know some basics, you're of course welcome to subscribe to my channel where I'm sure you'll pick up a couple things (although not necessarily the "right" way), but your best resource for great tube guitar electronics instruction is Uncle Doug's excellent channel. I recommend you subscribe to his channel, watch every video 20 times, and take notes. He's a great educator. You'll learn a lot! Good luck! ru-vid.com

+Frances Nieznay Thanks Frances! Always nice to hear your feedback.

thomas martinez if he sells.one to me I'll make it into a guitar

that amp will never have bad breath.

Sorry I missed your comment before... No, it isn't difficult. No more difficult than any other amp.

Ben Tanch I know this is old response but adding a 3-prong cord to any amp is simple the white and black or the hot leads that go to the two wires coming in now with black is your hot wire white as the neutral and the green wire just goes to the frame of the amplifier. Morning hope that helps you in case you haven't figured it out yet