Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dude on July 28, 2021, 12:50:40 pm
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It’s hard to find all the spec’s on the Hammond Organ AO-43 PT. We know it’s 325-0-325, but how many tubes can it supply...,that rating l can’t find? But from my experience l have run three 12ax7, two EL34’s, 5U4G, filaments and all with no heat issues with the PT, maybe “warm” to the touch after an hour of loud playing, which doesn’t mean it won’t blow, or does it? With 5Ar4 and 6L6’s, less warm.., if at all.
https://thesubjectmatter.com/calcptcurrent.html (https://thesubjectmatter.com/calcptcurrent.html)
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If you can find a schematic for the Hammond AO-43 amp, you should be able to see how many tubes are run by that power transformer, and calculate the load it can safely handle from that.
The AO-29 amp chassis has 7 preamp tubes, a pair of 6V6s and a 5U4 that it runs. That's a fair amount of heater power. I could calculate the mains power amperage capability based on the max draw of all those tubes if I wanted to push that PT.
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Google ;
1 X 12BH7
2 X 12AX7
2X 6BQ5
1X 5U4
http://solorb.com/elect/musiccirc/liltiger1/
https://www.tdpri.com/threads/help-me-convert-a-hammond-ao-43.991474/
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Thanks for the info, nice read. l added up the draw of the tubes l mentioned, 148mA rated PT is needed, preferably @ least 160mA. Just wondered if anyone found that info on this PT.
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It would be my guess that because the AO-43 PT is used with a pair of 6BQ5s, it's probably not going to have the current capability to run a pair of EL-34s. The EL-34s can draw a lot more current than the 6BQ5 will.
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It would be my guess that because the AO-43 PT is used with a pair of 6BQ5s, it's probably not going to have the current capability to run a pair of EL-34s. The EL-34s can draw a lot more current than the 6BQ5 will.
100% right
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Yes, Latole makes sense. But back in the day, Hammond made beefy PT's, that AO-43 PT seems to be able to handle more tube current draw then what it was designed for, as you mentioned in above post. We know the 5v tap is capable of running a 5U4G, the PT rating is 'not found anywhere on line" that I can find. But I used a 5AR4 and 6L6's for hours, (3, 12ax) with no issues, not even hardly warm so I decide to try EL34, same 5AR4 and to my surprise the PT was just a tad bit warm, played an hour checking if it got hot or much warmer, it did not.
My post was asking (since all we know what the PT was use for), can it handle more current draw, since it doesn't get that warm or hot doing so, this was my question, if I'm out to lunch, tell me.
Check this calculator:
https://thesubjectmatter.com/calcptcurrent.html