Hi all. I searched first but did not find an answer and would appreciate a nod in the right direction.
I have an AO-29 complete with tubes and would like to make a 5E3 or similar 15-20 watt amp. What I'm trying to determine is if my transformers from the 29 can be used. The PT is stamped 22111-4 but ink was used for the numbers on the OT and they are gone. They hung in there for about 60 years until I decided to clean the PT with a wet cloth. It was caked with dust and by the time I found them they were just a smudge.
I'm not opposed to changing other hardware but obviously hope to save a few bucks using the iron I already have if possible.
Should be fine for a 2x6V6 amp such as a 5E3. There are two versions of the AO-29. One has a PT with 320-0-320 HT winding, but the field coil model has a 380-0-380 HT winding. So, if you have the field coil model, your B+ will probably be higher than you expect.
I appreciate the reply. This is the info I've been looking for.
I've been busy and probably won't get to look at the PT again for a few days, but when I do I'd like to determine the voltage so I can move ahead with my plans. Is there anything on the PT that would tell me if the HT is 320 or 380? If it's 380 what would be the best method for dropping it? Can I get by with adding an appropriate zener to the CT?
I'm back on my 5E3 build with spare iron and other parts from the A0-29 and have a question about the PT. The part number is A-A0-22111 4.
I've tested the wires and have
6.7vac on brown-brown heaters
670vav red-red
335vac red\yellow center tap
But I have just one green wire instead of 2 as expected for the 5vac. I also pulled the cap off the PT to make sure one didn't break off but I didn't find anything.
Can someone tell me how I get my 5vac filament voltage for the rectifier?
That's it! The jpg shows the same outputs as mine. I thought I had a pic to upload mine but I either deleted it or save it to some odd folder. The voltages I posted above are unloaded with the PT sitting on a bench.
The yellow is 5.8VAC with 12 on the single green. Based on what I've found so far do you think I'll need to drop the voltage just a smidgen?
The yellow is 5.8VAC with 12 on the single green. Based on what I've found so far do you think I'll need to drop the voltage just a smidgen?
12 on the green??? What does that mean? How are you measuring that? What is the other meter probe connected to? The green has nothing to do with the yellow wires. The green is a center tap for the brown wires only. Did you do the continuity check I suggested?
I would not worry about the higher voltages on the 5v and 6.3v windings. Those are normal for an unloaded winding. But that 380-0-380 is not appropriate for a 5E3 amp. I would not recommend this transformer for a 5E3. This PT was used in the AO-29 that supplied a field coil speaker. The 700Ω field coil was placed in the CT of the HT winding and it dropped 100V. This has the effect of lowering the B+ by 100V. You would need a 700Ω/30W resistor to drop the B+ by the same amount as the FC does. If you are determined to use this PT in a 5E3 then I suggest you study the power supply schematic for the AO-29 and drop the B+ in a similar manner, or use some of the other more modern options for dropping the B+. The best solution is to use an appropriate transformer for the 5E3.
[/quote]12 on the green??? What does that mean? How are you measuring that? What is the other meter probe connected to? The green has nothing to do with the yellow wires. The green is a center tap for the brown wires only. Did you do the continuity check I suggested? [/quote]
Big mistake. It was wee hours late when I checked it and screwed up. I checked VAC across yellow first and missed moving the test lead to brown when checking the green CT. I also checked continuity several days ago when I wasn't at the end of an 18 hour day. I suppose it doesn't matter though. I was all but convinced the voltage was too high for comfort but wanted a second opinion.
picked up a Hammond m-111 last night for free. took a chance when i saw the drawbars in the Craigslist ad (I've only been burned by a solid state tonewheel Hammond once and i at least got something to use as a chassis from it)
did not realize all of the goodies inside!
nice to see sluckey has successfully added a 12ax7 to the tube complement. my plans are to use the two triodes for a long tailed pair and something princeton-y for the preamp, probablywith a simple one knob tone control. had also thought about using a pentode input (either 6au6 or 12au6). about to measure the transformers but the transformer on this appears to be similar to what was used on the ao-43 so I'll probably swap it for the puny transformer that was on the main amp. thinking a little 1x12 combo with a 12" organ pull cleveland speaker
the little 8" rola alnico will go with an 8" ceramic in a little single-ended plexi combo
PRR wrote:
Plotting loadlines is only for the truly desperate, or terminally bored.
Greetings - I am new to this forum and found my way from another forum post saying this Amp Garage group has the most expertise on Hammond amp conversions.
I recently acquired a stripped organ chassis with no backstory and am planning to convert this to a guitar amp (with the help of an amp tech). I would appreciate your help identifying what model organ this came from? and recommendations on what guitar amp circuits use transformers that most closely match these transformers (OT: AO-24924-0 524624, PT: AO-24110-1 9496220)?
FYI: My main amp is a Tweed Tremolux 5e9 circuit converted from a Hammond.
Regards
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