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Old 6th May 2013, 07:56 PM   #1
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Default Hammond Converion amps

I had a trashed Hammond M-111 dropped at my house a few weeks ago. I was going to go pick it up but the owner graciously offered to drop it off. He and his wife practically burned rubber getting out of my driveway when they unloaded it. I was told it was in better shape than it ended up being. The PO said it was was running but suddenly "wouldn't start anymore". I discovered the cause of that when I checked the power cord. Some yahoo replaced the original 2-prong cord with a grounded cord which seems like a safe, reasonable thing to do but rather than solder the new cord in place they just twisted the wires around the terminals by hand. Needless to say they didn't stay put and when one conductor came off it stopped running. They are probably lucky it didn't burn their house down. The PO then decided to put it outside on his porch where it spent the winter in the snow under a tarp. It has a lot of water damage and mice made a nest in the tone generator and gathered their nesting material by stripping the insulation off of wires and chewing up coils.
Needless to say it's toast now.

The amps looked pretty bad topside.

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But the damage seems to be mostly up top where 50 years of dust sat and acted like a sponge for the moisture it was exposed to.

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The speakers and grill cloth are surprisingly in great shape. So.........if this think is to live on in any capacity it will be as a few converted guitar amps. I've got a AO-44 & AO-29 to work with. I found a schematic and layout from Paul Ruby that used the existing tubes & transformers on the AO-44 to make an amp. It sounds interesting and I might give it a try but I was really hoping for something a little more AC15 like for it. The AO-29 seems to be a good 5E3 platform. That amp had a beautiful pair of Sylvania black plates in it. Has anyone done either of these? If so do you have a layout handy?

Thanks in advance.

Last edited by Riff12571; 7th May 2013 at 08:04 AM. Reason: typo correction
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Old 7th May 2013, 02:16 AM   #2
scrimpu is offline scrimpu  United States
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The AO-44 makes a sweet little amp with very little modificaion, very bright and jangely sound. I removed the transistor input stage and added a socket for a 12ax7 to mine. The AO-29 makes for a great 5E3 and leaves you several extra tube sockets to experiment with. I recommend gutting this one and build to suit your needs.
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Old 7th May 2013, 08:08 AM   #3
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That sounds a little closer to what I'm after. Did you find a schematic for that or did you go without. I'm kind of new to this and still have to follow a road map as I go. I've made repairs and have biased my own amps for years but I'm not really good on theory at this point.
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Old 9th May 2013, 06:27 PM   #4
scrimpu is offline scrimpu  United States
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Paul Ruby's site has a good example of what to do with the AO-44. For the AO-29 I stripped the original circuit board and rebuilt it copying the 5E3 layout. Remove everything but the heater wiring and rewire as a 5E3 or whatever you like. The power supply will also need some modification.
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Old 10th May 2013, 02:13 AM   #5
cancon is offline cancon  Canada
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captain-foldback.com is a great resource for hammond/leslie schematics.
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