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Hammond M3 organ conversion to 18W Marshall TMB - first build attempt.

Discussion in 'Shock Brother's DIY Amps' started by GreenMagicMan, Aug 23, 2020.

  1. GreenMagicMan

    GreenMagicMan Tele-Meister

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    Tomorrow I get a Hammond M3 organ (free! I am very excited!!)
    My aim is to build a 18W Marshall TMB clone with all the harvested parts.
    I feel a little bad to chop up an intact USA built high quality M3... but I want an amp! And if I don't get it it's going to get tossed very soon anyway. I don't play piano and never will. Owner got it as a leave behind when he either rented or bought his place. He said prior owner said it wasn't working 100% and 'needed a tube'. That's fine by me.

    Planning to use the chassis, the OT, PT, tubes, tube sockets, 12" speaker, wood from cabinet to built a speaker cab. Should be the AO29 chassis in there.
    I have unlimited quantities of 18 AWG, 12 AWG, 14 AWG, 10 AWG (and smaller) wires, quite a few caps from 1950s voltmeter and (2) low value pots, several orange drop caps, and some others from various harvested devices.


    Total newb to amp and builds.
    That said, here's my creds (SKIP this blah blah part to below - recommended):
    Homeowner and I do all my own wiring and circuit adds and upgrades and troublehshooting.
    I hand built and wired up (4) 240VAC circuits and (1) 480VAC tri phase for a Baxter commercial rotating oven for a commercial kitchen in fussy picky Berklee California several years ago (after creating plasma through a nearly fatal infinite energy draw mistake after four 15 hour days...) Did the box ties ins to the 200A breaker box for about 7 circuits in that kitchen.
    I DON'T do hot tie ins or any of that crap I've seen done on a few film shoots either. I always take the whole box down and work 99% one handed in a mains breaker box.

    I've hand wired a lot of AV gear. I saved a film shoot in SF by rigging up 24VDC power from two 12VDC items I wired in series and hooked up to a $100K rental Arriflex SR3.
    I've hand designed and soldered a lot of small DC devices over the years.
    Tons of motorcycle and car work including some serious electrical problem fixes and some seriously hard to find and fix ones. Electrical demons can be the hardest jobs to banish from a car!
    And I wired up my cherished #1 player the 1979 prototype Washburn A20V guitar when it was gutted with no electronics.
    I do a lot with metal and do a lot of custom shaped metal builds for smaller items with some crazy fussy details. I'm quite adept with a $9.99 angle grinder with thin cutoff wheel, I'm a DIY freak, swap shop and repurposing King. I love creative re-use of old / other things, and on top of it I am CHEAP :)

    SKIP to HERE ----->
    So... that out of the way... I have no idea about amps (heh) and am just learning about them all this weekend and learning terms like OT, choke, PT, B+ etc... So I've got some huge learning curves ahead of me. I will document the build here (and on my personal blog as well) and I'm sure will have lots of questions.

    I read thru and listened to Kley de Jong "organ donor" AO29 amp build. That's frankly a big inspiration as I learned thru that thread about Hammond conversions. I also like the Mojotone Marshall 18W TMB page with the video and think the tone there sounds fantastic.

    My only amps are small practice and thought to be 'crap' by most as they are SS (solid state: Peavey Vypyr 15 and Vox AD15VT - Valvetronix. Single tube amp with SS.)

    Points, thoughts, do's and don't's will be immensely appreciated.

    After bypassing the entire 200A breaker box in that commercial kitchen and taking the entire building out by blowing the building mains 110A single breaker on the tri phase... I now have a healthy and hopefully appropriate fear / respect for electricity. I used to have an admittedly sort of invincible attitude to it (not quite, I would do breaker box circuit ties ins one handed with rubber soled shoes and try to use plastic handled screwdrivers etc...).

    I DO have a hospital medical grade ISO transformer on hand! Could I / should I use this inline to the amp once I start powered up testing to save me getting shocked?

    Here's the ad that's been spinning my head since Friday. No details at all, but I figured out the model by that single photo online.
    00y0y_6UM5InWExz8_0mj0Hz_1200x900.jpg
     
    Last edited: Aug 23, 2020
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  2. Nickfl

    Nickfl Friend of Leo's

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    Lookup and build a "lightbulb limiter". you should we use one for startup on any new build or modified amp. A lot of new builders miss this point but it could save them a lot of time and sometimes the expense of a new transformer when things go wrong.

    Can you read a schematic? And do you have a schematic for the original Oregon? That will help a lot in determining what you have and have suitable is for what you want to build.
     
  3. schmee

    schmee Doctor of Teleocity

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    Yeah too bad to chop up a Hammond. I had one, it's more work to try to use the amp than starting afresh. There is no usable pre amp really.
    But, boys will be boys!
     
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  4. Peegoo

    Peegoo Poster Extraordinaire

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  5. GreenMagicMan

    GreenMagicMan Tele-Meister

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    Thanks all!
    Yes, I can read schematics. Had to learn them for moto and car electrical diagnosis.
    I've glanced at some so far, but not studied them yet. I do want to verify in person what is in this M3 - like if it's the AO 29 or something else.
    I had read about that lightbulb limiter thing, although not fully understood it. Is it almost like a 'fuse' and the bulb blows rather than take out the OT or PT?
     
  6. tubegeek

    tubegeek Friend of Leo's

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    A light bulb limiter (LBL in the local jargon) will only allow as much current through it as its wattage rating permits. The amp (Device Under Test aka DUT) is powered in series with the lamp. Suppose your amp's power supply behaves as a dead short for some unexpected reason. Then it is nothing more or less than a few inches of wire in the bulb's AC supply. The lamp will happily light up to its stated wattage rating and draw the corresponding current that it normally would. Visual indicator of a problem. Suppose the DUT is less onerous load than that - then the amp will limit the current through the series circuit with the bulb and it will not glow much, if at all. Visual indication that the DUT is not going to blow fuses when the LBL is taken out of the circuit.

    Saves a lot of cursing and trips to that nice fresh breaker box in the basement!

    Welcome!

    A shame about that organ.
     
  7. GreenMagicMan

    GreenMagicMan Tele-Meister

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    Hmmm, I can also get on this trip another Hammond M2 with AO 14 chassis
    -or -
    another Hammond "M1124"unit number (not sure which this model really is) with built in Leslie Tremolo circuit.

    All of these 3 Hammonds are free you haul away deals, and I'll be heading out of VT with a massive extended E350 van so i could grab two.
    Thoughts? I'll try to figure out which model the tremolo unit is.

    RE- Edit: I think it's called an Phoenix organ from 1972 and wiki says it's a 'transitor' model so likely it's too 'modern' for proper vacuum tubes and not the unobtatnium one to get. So will plan to skip that one at least I think.
     
    Last edited: Aug 23, 2020
  8. tubegeek

    tubegeek Friend of Leo's

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    You'll want the tremolo if it's what I think it is - containing the unobtanium saturable reactor (multi-tap inductor.) That part is the key to unlocking pitch shifting vibrato, similar to the legendary Magnatone vibe.
     
  9. Nickfl

    Nickfl Friend of Leo's

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    If you're heading out there prepared to move two I'd say take all three if you can.

    They're either worth restoring or parting out, and like you said there's a good chance they'll otherwise end up in the dump if they've gotten to the point of "free to whoever hauls them away".
     
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  10. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    If it is for free, the transistor organ is of the right age to harvest chips and transistors for pedal builds.

    I know you said you are cheap. Do yourself a favor and get a Hammond 1750PA output transformer. The ao29 OT is not what you want for a 18W. It will make sound but... spend a little for this. $37.80 at Mouser.
     
  11. GreenMagicMan

    GreenMagicMan Tele-Meister

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    Ok, thanks for the recommendations.
    I have read thru a bunch of places that seem to think the 'iron' PT and OT (right?) are good to great build quality in the Hammond M series. Do you think that's not the case with the OT? Like too noisy or lousy tone?

    I believe I have resolved to get 2 of the organs. Only 2 are all tube.
    The earlier M2 organ with Hammond AO-14 chassis seems to be a very nice setup to build a Fender Tweed Deluxe.

    So... as I have two places I jump from often I'm thinking build two amps!
    Maybe the Tweed first as it appears to be easier.
    Then the Marshall 18W TMB with some extra add ons sounds very appealing to me.
    From just the internets and my taste in (dirty) music I feel pretty sure I'll love the Marshall the best.
     
    Last edited: Aug 24, 2020
  12. RollingBender

    RollingBender Tele-Afflicted

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    Hammond organ PTs are very robust, powering things other than just the amplifier. I think the OTs are a bit weak by guitar standards because the didn’t push the amps near as hard as a guitar circuit will.

    You’ve probably seen this said before and I’ll say it again as someone who has done a few “organ donor” amps... Iron and tube sockets, yes. Chassis, yes if you don’t have means of making a new one. All that wonderful black solid core pushback wire going from amp to tone wheel to keys, ABSOLEUTELY! ...that wire is a dream to work with. Everything else, forget it... drifted components, specs different from guitar circuits, etc... not worth the hassle. You put a lot of work into any amp. No use tying one hand behind your back (until it’s time to poke around inside a live circuit).
     
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  13. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    It depends on several factors. You will find the OT is very small compared to OT's of similar guitar amps so probably bass frequencies would not be similar (there would be less). The winding ratio of the AO-20936-2 would be correct for a 2ohm load. (I am not sure of the OT you may find in yours.)
    As @RollingBender pointed out I think you will find them weak, and lacking.

    The OT might be just the ticket for a 12au7 type push pull microamp. So don't just chuck it.

    The PT in these are great. The filament secondaries can handle more than anything you will throw at it.
     
  14. GreenMagicMan

    GreenMagicMan Tele-Meister

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    Thanks for the tips!!
    Yes, I'll keep the transformers for some usage somewheres...
    I also might pick up on this trip tomorrow a:
    130 Watt Peavey Standard Series 260 PA / amp / Mixer sort of thing for $10.
    Non functioning - but I could simply use the cab perhaps if it's big enough or the knobs and some of the metal and maybe anything else scroungeable. I see it's SS but I guess an interesting workhorse.
     
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  15. tubegeek

    tubegeek Friend of Leo's

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    You're gonna need a bigger garage, you keep this up.
     
  16. GreenMagicMan

    GreenMagicMan Tele-Meister

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    Ha, yes. Although home small, garage huge. Go figure.

    Is that non working Peavey that 'might need transistors' and a 'project' or for parts a must get for $10?
    I havent had time to look up what diodes, caps, pots etc are in that thing.
    Or should i try to sort it out as a guitar amp? Or pass?
     
  17. Jesco

    Jesco TDPRI Member

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    I would pay $100 just for the wire. It is so nice to work with.

    To bad about chopping a working Hammond. As I watch 500-1000 year old redwood forests burn here in California, I can’t help thinking about what fools they think us 100 years from now when every Hammond has been chopped for its amp and people realize what a majestic machine it is. They will never be built again.
     
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  18. Mouth

    Mouth Tele-Afflicted

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    I'd hit up someone who sells hammond organ parts and see if they'd give you enough to buy an amp or amp kit.
     
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  19. GreenMagicMan

    GreenMagicMan Tele-Meister

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    Understood. I feel slightly conflicted.
    I got both last night, crammed them into a cargo can. First one was a breeze, second one was not.
    The second one is the M2 but it's stamped 'M' on the back. The finish is very beat up, the cheaper laminated option - not particularly nice looking new and pretty horrid now.
    Owner posted: "Powers up and plays, all drawbars, keys, pedals and switches work. Volume is very low and fades after a few minutes into a fuzzy static noise. I suspect it needs new tubes, but it's not a project I'm interested in."
    No one will want that one. I'll chop that one first.

    The M3 has the more expensive Mahogany finish and does actually look quite nice if you like that older 50s look.
    Neither had a bench or an external speaker. Both had some flopping around thing, I guess either the keys or the tremelo. I tried to tighten up the (4) hex bolts on the M3 and the (4) flatheads on the earlier M for transport. It helped with the noise.
    The second picked up one (older beat up M) had to get tipped on it's side and down not "4" but 7 steep steps that was too tall for the ramps I brought, and it looked like a kid carrying a pig as it bumped down the steps.

    The M3 I'll have to check out because it's not working, maybe it powers up no sound or maybe it doesn't. Wasn't clear from guy I spoke to on the phone. And I picked it up late put out behind his building so no face to face questioning.

    Sidenote:
    Sorry, the forest fires suck out there. I have very mixed feelings and memories of California. A love / hate relationship if you will. I will say at it's best for me it has some of the most outstanding motorcycling touring roads in the world ('Norcal' really Bay Area was my base). I've two wheeled it all over France, Holland, Belgium, Switzerland, dipped into Spain, Italy, Indonesia, China and New England of course. Nothing beats the Sonora Pass. Taxes, drought, no water, and the f u attitude of liberals to anything but left I can leave.

    I am chomping at the bit to dig into the amp build(s)!! These will wind up in VT and I think the only way I can get them back to where I'll operate is in pieces as I only have either a lowly SUV on tap or a large 2 door coupe which is the likeliest final leg journey car I'll use.

    This more or less summed up the feeling last night:
    scr-pigpiratesteamwork.jpg
     
    Last edited: Aug 26, 2020
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  20. GreenMagicMan

    GreenMagicMan Tele-Meister

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    In several weeks, once I'm elbow deep into this, should I bring this along:
    Medical Grade Isolation Transformer.
    Dale Technology, NY. Model IT1100
    Input 120 VAC 8.0 Amps
    Leakage current: 75 micoramperes, MAX
    Output voltage 125 VAC
    Output current: 8.0 Amps
    22 lb toroidal transformer.

    Would this help with potentially lethal shocks and infinite energy draw mistakes?
    from Dale:
    "the use of a Dale Technology Medical-
    Grade Isolation Transformer can
    help reduce the danger of micro- or
    macro-shock, as well as bring system
    electrical-leakage current within
    acceptable limits."
     
    Last edited: Aug 26, 2020
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