Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: imgumby001 on November 26, 2020, 12:56:32 pm
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I've got a couple AO-43's laying around that I'd like to do something with. Also, a bunch of 6BQ5's. My question is what circuit works best with the tranny's from the old Hammonds, as well as, is there a circuit that incorporates reverb? I'm aware of the Hammonator circuits, but are there any other common ways the transformers are re-purposed?
Thanks All
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bunch 'o stuff came up searching "AO-43" here
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November Plexi, or 6V6 Plexi, I can provide a layout for a board that fits the AO-43
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November Plexi, or 6V6 Plexi, I can provide a layout for a board that fits the AO-43
Dude, Hell Ya!! That would be awesome!!!!!! I've got another chassis, but I'd love to reuse at least one of the Hammond's.
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Just downloaded Slucky's November schematic. Looks like that's an incredible option. I'll keep searching for a sweet 6V6 plexi schematic.
Thanks Guys!!
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The pic l posted was a 6V6 Plexi, the same as the November’s EL84’s. But you have to enlarge the sockets to fit 6v6s, a tricky job. I ended up cutting out both power tube holes, a rectangle cut, added a plate and cut two 1” socket holes, very tight and has to be precise. I could give you the details but much easier to just do the November. There was a post a few days ago about the fixed biased EL84’s in the November vs K bias. I was thinking about building the November but with cathode bias, rather than fixed. Sluckey’s layout won’t fit in the AO43, too wide and too long. l used his basic layout out changing the arrangement. Unfortunately, l don’t have the ability to use the software he did. But l have a nice hand drawn board with the layout that fits great, a little narrower and also the turret holes locations in another drawing. I’ve done three AO43’s to Plexi’s, made some mistakes but now l got all the measurements and locations down pat. If you’re serious let me know and l’ll post the the hand drawn layout, turret bd size and location that works best. I sure wish someone could take my layout and make a nice Visio copy but let me know. If you go with the 6v6s it’s a lot of extra work, l’d keep the EL84s (recommended). l can make the small changes needed the layout for either fixed or K bias.
I also made faceplates from a free program and had them printed, l can send you the info and you can print it out on heavy paper or take the file to Staples, or l can send a faceplate and a cut piece of plexi glass to fit perfectly, $5 plus shipping. I just covered the faceplate with home depot 1/16” Plexi glass, have the drill out pattern too. Search AO43 Plexi for pics of my faceplate or l can post. Good luck. Reverb won’t fit, but a pedal works.
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The pic l posted was a 6V6 Plexi, the same as the November’s EL84’s. But you have to enlarge the sockets to fit 6v6s, a tricky job. I ended up cutting out both power tube holes, a rectangle cut, added a plate and cut two 1” socket holes, very tight and has to be precise. I could give you the details but much easier to just do the November. There was a post a few days ago about the fixed biased EL84’s in the November vs K bias. I was thinking about building the November but with cathode bias, rather than fixed. Sluckey’s layout won’t fit in the AO43, too wide and too long. l used his basic layout out changing the arrangement. Unfortunately, l don’t have the ability to use the software he did. But l have a nice hand drawn board with the layout that fits great, a little narrower and also the turret holes locations in another drawing. I’ve done three AO43’s to Plexi’s, made some mistakes but now l got all the measurements and locations down pat. If you’re serious let me know and l’ll post the the hand drawn layout, turret bd size and location that works best. I sure wish someone could take my layout and make a nice Visio copy but let me know. If you go with the 6v6s it’s a lot of extra work, l’d keep the EL84s (recommended). l can make the small changes needed the layout for either fixed or K bias.
I also made faceplates from a free program and had them printed, l can send you the info and you can print it out on heavy paper or take the file to Staples, or l can send a faceplate and a cut piece of plexi glass to fit perfectly, $5 plus shipping. I just covered the faceplate with home depot 1/16” Plexi glass, have the drill out pattern too. Search AO43 Plexi for pics of my faceplate or l can post. Good luck. Reverb won’t fit, but a pedal works.
Ya dude, seriously, send it to me. I’ve got two completes, and a ton of 6bq5’s. Plus, 5u4’s, 5y3’s, and just about every other suitable recto tube you can think of. Reverb is no deal breaker on this as I have a friggin MONSTER of a PT I got out of a magnavox radio that will easily power a big circuit I was thinking of using for a slo100 circuit w/reverb. Right now I’d like to use as many parts I already have as possible. Hell, I’d love to reuse the AO’s cone boards, we have about five or six of those lying around! Whatever you’ve got would be super appreciated!!!
Thanks again
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I'll add $.02 - IMO you can use that iron with nearly any simple 2xEL84; 2x6V6; 2x6973 amp. The problem will be narrowing it down to what you want. Adding reverb will depend on the amperage draw of the particular reverb circuit. Others here have a lot more experience with reverb circuits than I do. As far as reusing cone boards. I have done it. PITA, but if you are being conscientious about resources, I applaud. It worked for me but was too time consuming and generated too many solder fumes. I think its a sketchy idea to reuse the old solder, so getting the cones empty is the hard part. Once clean you can populate the board with all components and leads and solder away, applying heat to the outsides of the cones.
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I reused a cone board on one project. Cleaning it was easy but very messy. I recommend long pants, long sleeves, long leather gloves, and safety glasses or face shield. And only do this outside! Lay out a piece of cardboard on a table. Set up your soldering station and air compressor. Best to secure the cone board in a device such that you have easy access to both sides of the board. Remove any components from the board. Now put your iron on the cone side and melt the solder and put the tip of an air compressor nozzle on the component side and blow the solder out. (You don't need 100psi for this!) You end up with clean, shiny, pre-tinned cones and a big disposable mess. Solder splatters brush off the board pretty easy. The whole process only takes a few minutes if components have already been removed. Lot's of fun but I won't be doing another. :icon_biggrin:
Here's the board I did...
http://sluckeyamps.com/RCA/RCA_07.JPG
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I never thought to use compressed air, that would have sped things up a lot. But like Steve, I am still one and done, on reusing cone boards.
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I did the same thing as Sluckey with an AO43 cone bd. I made a 6V6 Plexi on that bd. You could build the November on that cone bd too, much easier keeping the same power tube holes.
Here's the faceplate I made, heavy paper sandwiched between the chassis and 1/16" plexiglass from home Depot.
I added a PPIMV too, blue and green wires over the top to the dual pot, works ok but I only turn it down a little while mixing it with pre master vol, plus you get normal and bright volumes. You don't need that monster PT, use the Hammond AO43 iron, works fine. puts out about 390B+
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Thanks guys!! I’m wondering if I can just clip off the cone ends and just drill out the centers in the drill press. I know that would kill the cone, but I wonder if I’ll end up with a useable eyelet board. Maybe I’ll try one and see. After my current build I’ve already decided in using sluckey’s November specs for one of my sets of trans. I read in another thread my reverb tanks met not work as I thought they will, so that’s going to need research and possible a rethink...
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Man, dude!! That looks amazing. What a great job. I can only dream about making something come out that nice!!!
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Maybe I’ll try one and see.
All that work cutting the cone and drilling, be faster to heat the cone and blow it clean. One recommendation would be to shorten the cone length, gets close to the chassis bottom, you could use protection board under, probably better then cutting the cone. But without compressed air, very hard to get that cone clean.
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The AO-43 reverb tank is made for a cap coupled driver circuit. It won't work in a transformer driver circuit. You may want to look at the AO-43 schematic. You could use that reverb circuit or browse through some Ampeg or Magnatone schematics. Many of those use a cap coupled driver.
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Just noticed that the November has switchable cathode and fixed bias.
I know it was asked in another thread about the tone differences. But Sluckey made that layout and l assume the amp, what was the tonal differences between fixed and cathode, just in general. I assume the fixed is cleaner a bit longer before breakup, cathode more like an 18 watt? But a totally different circuit though..?
Would that AO43 PT be to much voltage for EL 84’s with a 5Y3
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I built the November shortly after I revived my interest in tube amps. So I was trying out all the cool circuits I read about. I built another November shortly after the first. It had none of that "magic" stuff. The second amp still lives. That "hot rod" November became a donor for a Matchless Lightning, which became a donor for a Vox AC-15.
I never heard enough difference between fixed and cat bias on the November to justify the extra complexity.
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Maybe I’ll try one and see.
All that work cutting the cone and drilling, be faster to heat the cone and blow it clean. One recommendation would be to shorten the cone length, gets close to the chassis bottom, you could use protection board under, probably better then cutting the cone. But without compressed air, very hard to get that cone clean.
My biggest issue is no compressor. But, the clip/drill thing was a dismal failure. So ya, probably just shelf those boards for now.
The AO-43 reverb tank is made for a cap coupled driver circuit. It won't work in a transformer driver circuit. You may want to look at the AO-43 schematic. You could use that reverb circuit or browse through some Ampeg or Magnatone schematics. Many of those use a cap coupled driver.
I also have a tank for a conn organ, but I’m wondering if it’s not just the same issue with that one.
I built the November shortly after I revived my interest in tube amps. So I was trying out all the cool circuits I read about. I built another November shortly after the first. It had none of that "magic" stuff. The second amp still lives. That "hot rod" November became a donor for a Matchless Lightning, which became a donor for a Vox AC-15.
I never heard enough difference between fixed and cat bias on the November to justify the extra complexity.
What do you mean by “magic”?
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I never heard enough difference between fixed and cat bias on the November to justify the extra complexity.
I hear ya, that ground lift filament CT and l assume a bleeder (all in one) extra stuff before S/B switch isn’t really needed. I’d just skip all that, l guess if l had hum, l could just lift the filaments CT to 84’s cathodes. Bleed the caps with a 2W 220K off first filter. Why the 2W biasing R’s, l never had an issue with 1/2W? Am l correct the small tag supply bd is to lift the filaments and provide a bleeder R for Power Suppy?
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l guess if l had hum, l could just lift the filaments CT to 84’s cathodes.
Not if using fixed bias. :icon_biggrin:
Why the 2W biasing R’s, l never had an issue with 1/2W?
Ain't no 2W biasing resistors. The 100K is 1 watt. The other two bias resistors are 1/2W.
Am l correct the small tag supply bd is to lift the filaments and provide a bleeder R for Power Suppy?
The main reason for that terminal strip was to connect the salvage PT wires which were only a couple inches long. I did put the elevation components on the same terminal strip.
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Thanks for the reply’s, good point on lifting the filament ground to the 84’s cathodes, switch that to fixed, big problem (l could have missed that, thanks). My mistake on the 2W biasing R’s, l meant the 1 ohm 2 watts off the cathodes for meter biasing points. But no a big deal, many here use 1 watt and more. Cheers
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My mistake on the 2W biasing R’s, l meant the 1 ohm 2 watts off the cathodes for meter biasing points.
I used them simply because I had them. They are 1% tolerance.
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What do you mean by “magic”?
same a "secret sauce"
It's that moment you plug in, play and you just "know" this is a good amp
being a techy, it's real hard to see with a scope :icon_biggrin:
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What do you mean by “magic”?
same a "secret sauce"
It's that moment you plug in, play and you just "know" this is a good amp
being a techy, it's real hard to see with a scope :icon_biggrin:
For a minute there I was thinking I missed something in the thread. I guess I understood better than I though. Thanks for the clarity bub!
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The AO-43 reverb tank is made for a cap coupled driver circuit. It won't work in a transformer driver circuit. ...
If you call it "choke coupled" then you "can" use a transformer. Just use the primary.
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The AO-43 reverb tank is made for a cap coupled driver circuit. It won't work in a transformer driver circuit. ...
If you call it "choke coupled" then you "can" use a transformer. Just use the primary.
Nice! Thanks PRR!
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The AO-43 reverb tank is made for a cap coupled driver circuit. It won't work in a transformer driver circuit. ...
If you call it "choke coupled" then you "can" use a transformer. Just use the primary.
Nice! Thanks PRR!
But it ain't choke coupled. It's cap coupled.
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The cones on those cone boards are "fun" to clean out with a soldering gun and a solder sucker...
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heat them all the way, most of the cones have a little notch in the bottom where solder can drain out. I believe I cut the tips out like one would a piping bag for icing. Ive reused those boards to great success. Not that bad, heat and remove leads.
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heat them all the way, most of the cones have a little notch in the bottom where solder can drain out. I believe I cut the tips out like one would a piping bag for icing. Ive reused those boards to great success. Not that bad, heat and remove leads.
At some point I’m compelled to do it. They’re just such nice little boards, it’s hard to justify trashing them.
The cones on those cone boards are "fun" to clean out with a soldering gun and a solder sucker...
My braid certainly WON’T do the trick! ;)-
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No compressor, try a can of keyboard cleaner. Not sure if there are chemicals that would inhibit solder, read contents. Try Staples.
There are slits on the end of the cone, any forced air would clean the solder out leaving it tinned.
I agree those cone bds are small and great for some projects. Only issue is they are a bit long, you have to raise the bds at least 1/2” or use protection under.
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No compressor, try a can of keyboard cleaner. Not sure if there are chemicals that would inhibit solder, read contents. Try Staples.
There are slits on the end of the cone, any forced air would clean the solder out leaving it tinned.
I agree those cone bds are small and great for some projects. Only issue is they are a bit long, you have to raise the bds at least 1/2” or use protection under.
I was actually at ACE sourcing stand-offs for my current build and they have plenty of choices, much to my surprise. Clearly the chassis would have to be relatively deep to accommodate its height, and, if you chose, the height of taller components like filter caps if they were board mounted. But plenty of people have done it, so clearly it’s doable, even by me.