Ultimate Hammond Conversions thread

[donzoid]

Thanks for clarifying Patrick. I knew it had to be one or the other resistor based on its size.

[mmmoser]

Sorry to come late to this thread. I have used many of the Hammond Family of organ amps and build dozens and dozens of successful amps from them.
As a rough guide, I have used the following amps for different builds:

AO44 amp can become a great low wattage clean amp or I have used the iron to produce a 10 watt mini-bassman from it (Little Wing circuit). Also I have used it to make a really great sounding mini chassis 18 watt Lite IIb circuit by carefully planning a very small board and changing to EL84 power tubes.

A039 has been used to build Spitfire, Vox and Marshall Lite IIb style circuits and several variations thereof. Downside is the 4 ohm output transformer but a Spitfire used a mismatch like this anyways. I tend to control voltages by varying the rectifier type. There is not enough room on the faceplate to make a more elaborate amp- I guess you could use mini pots, but I tend not to like them. Fine for pedal builds but that's only 9 volts.

A043 has been my go to amp for the Matchless Lightning circuit. I use the stock choke with no issues. I have also changed the Power tube sockets over to 8 pin units to build several Fender amps like the tweed deluxe or a tweed Bandmaster.

A050 amp is much harder to find but it makes for a perfect 18 watt Plexi foundation. There is the required room inside to get the proper layout to avoid interference in the higher gain circuits. These chassis seem to fit a Marshall small box head pretty well as a bonus but you need to add an oversize faceplate to fill up the standard Marshall chassis opening at 2.5".

AO35- makes a fine Carman Ghia- since its the original amp used when production started. Also any Marshall/Vox circuit that uses the tube socket complement. These are a little over priced on the used Ebay marketplace these days but all the Organ amps are getting expensive it seems.

Observations: I use my ESR meter and find at least 90% of the original can caps are still well performing and no leakage at all. I have never had a bad power or output transformer in any of these donor amps over the years. They can come with some truly great tubes as well. I tend to strip out all the guts and rebuild with either point to point or a carefully sized circuit board- I try to reuse all the wire that came in the amps, you can almost get an entire amps worth of wire for your new build from what came in the donor amp.
Soon prices will get to the point where the economics of building from them will go away and the switch over to all new parts will make more sense.

[donzoid]

Great info mmmoser....Thanks! That isn't the first time on this thread that those old can caps have been re-used as they test good. One thing I found in researching these old organs in general was that Hammond didn't cut corners on their design OR implementations...even with the tubes, they "premium-selected" what they put in. A terribly over-used term nowadays, but in that time span, it meant the better testing USA and European tube lots they could get. That's good for those of us who are enjoying what we get from them. They aren't new, but most of the ones I have yielded test just like it, and sound great.

[billc]

Thanks to all for the good info and inspiration in this thread. I have a AO-68 complete with reverb and it worked when I pulled it out of a K-133 organ. Am planning to built it into an Ampeg clone as the tube lineup (12AX7, 12AU7, 2 x 7591, etc.) makes it a natural and I'm looking for jazz tone anyway. Am hoping I can reuse the wood from the organ cabinet for a new head cabinet.
BTW, anyone know where to find an AO-68 schematic? I tried Google and no luck so far...

[donzoid]

Hi Billc,

If you meant an L-133, have you tried captain-foldback.com? They have quite a few schemo's there.

Edit: I see there ARE K-models in their line, using the AO-68. They are not on that web site. If you find a good link please share. I have the best success looking for the service manuals, they all have very good layouts and schematics.

[billc]

Hi Billc,

If you meant an L-133, have you tried captain-foldback.com? They have quite a few schemo's there.

Edit: I see there ARE K-models in their line, using the AO-68. They are not on that web site. If you find a good link please share. I have the best success looking for the service manuals, they all have very good layouts and schematics.

Thanks, I'll probably go that route, was unable to find one for free but found K-100 series manuals for sale starting at $10......FWIW also found a reference to the AO-68 here that indicates that is is definitely worth the effort
http://ampgarage.com/forum/viewtopic.ph ... 42e198af6d

[billc]

Hi Billc,

If you meant an L-133, have you tried captain-foldback.com? They have quite a few schemo's there.

Edit: I see there ARE K-models in their line, using the AO-68. They are not on that web site. If you find a good link please share. I have the best success looking for the service manuals, they all have very good layouts and schematics.

Thanks, I'll probably go that route, was unable to find one for free but found K-100 series manuals for sale starting at $10......FWIW also found a reference to the AO-68 here that indicates that is is definitely worth the effort

http://ampgarage.com/forum/viewtopic.ph ... 42e198af6d

[billc]

sorry, duplicate due to weird error message on first try...

[eniam rognab]

hey friends! slow and steady progress juggling work and school. got all the metal drilling and punching done and i couldnt help throwing the tubes in for a gander. i also found an IEC socket with an EMI filter so i thought i would cram even more shit in here! really looking forward to the weekend (in the future) i can just lock myself up and get some solder flowing!

[donzoid]

Looks really good Neal.

I have struggled the last few days with fitting all of the stuff into the existing chassis and layout. RE-engineering....wow...what a learning experience.

You were better off getting that new chassis and locating the stuff where you wanted it! That said, I warmed up the existing 'Lytics can caps for sev. hrs per the "reforming" processes described elsewhere online and (well I'll be darned) these caps are holding their charge like champs.

I finally got some solder flowing last night to build the tagboard. This is looking like a total "junkyard" build on my end. I salvaged several tagboards from an S-series, some CC resistors, used some that a little birdie used for packing material (thanks...you know who ya are), and now to save what appears to be precious space I am going to re-use the can caps (2 dual 50/450) as the main filter and first step-down reservoir. I pulled the one off the far end of the chassis (a single FP 50) and the choke. I'm going to try Fowler's method and put in a 2K2 and see what it sounds like...if I put the choke back in, I already drilled holes for mounting it near the rectifier tube socket "just in case".

[donzoid]

Funny but so far through this build, I kept telling myself it isn't worth the extra hassle of salvage/rebuild....then I end up picking this up for the cost of gas...

[xtian]

Nice. Those "two times per year" organs are the bomb!

See that silver junction box on the bottom right? I made the mistake of listing that on eBay for $10. It got snapped up within minutes of posting.

[donzoid]

Yep... looks like more salvage amps comin' for sure. My biggest regret now, is I had the Leslie cab and cable to plug into that box, plus both switches just sitting there for ten years. Then, six weeks ago...I sold them.

[eniam rognab]

hey don, thanks! yours is coming along nicely too! so you brought the choke closer to the PT? thats funny about the switch holes, its crazy how much space that beotch takes up! i didnt wanna screw around so i just mounted her in middlest place

i am quite interested in how the old 'lytics perform. i did unspeakable things to mine so now yours are that much rarer!

[donzoid]

Ahh....youth. I used to enjoy blowin' stuff up too. Now I just wait for the latest mistake. It never takes too long, I still get to see it now and then.