So my son and I both love to tinker and build things, we are both very much into music, and we are looking at picking up a locally sourced Hammond ao-43. He plays the bass and I TRY to pluck around on a guitar....lol. I have always loved the Matchless Lightning tone. My problem is that i know just enough to mess things up. After overlooking the schematic I have highlighted a few areas to make sure if I am correct or not in my thinking. I am going off of the Trinity TC15 layout and schematic. We are trying to reuse the transformers. I know the power transformer is HOT since it is 315-0-315 and the trinity spec'd PT is 290-0-290 but I should be able to make it work, right? The output transformer should work as well but it will only be 8ohm, right? I will also need to just eliminate the crunch/munch switch?
When going through the schematic i was unable to locate capacitors 20-29 and 38.
Hammond ao-43
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Hammond ao-43
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Re: Hammond ao-43
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Re: Hammond ao-43
380V is highish for an EL84, make sure you use good ones
He who dies with the most tubes... wins
Re: Hammond ao-43
Well I was most likely looking at a zener to drop the B+ into the acceptable range.
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dorrisant
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Re: Hammond ao-43
You can use this to drop what you need off the B+...
https://tubeamparchive.com/viewtopic.php?t=27035
https://tubeamparchive.com/viewtopic.php?t=27035
"Education is what you're left with after you have forgotten what you have learned" - Enzo
Re: Hammond ao-43
I was also looking at possibly using a 5Y3 in place of the 5AR4 and this should drop voltages some. not sure if that change alone will be enough but i can always try it and if i need more then use a zener. I'd actually probably do it with the 5AR4 first with the zener and then try it with the 5Y3 to listen for any tonal differences and stick with what i like the most. If anyone gets a chance to check out the attached files and give me feedback on my understanding, that'd be great. Thanks for the help already
Re: Hammond ao-43
Yes a 5Y3 has a bigger voltage drop than 5AR4. Make sure the reservoir cap is around 16-22uF.
He who dies with the most tubes... wins
Re: Hammond ao-43
The EL84 screen grids are fed via a total resistance of 23k5, and so are down in the 240s at idle, will drop maybe another 50V under overdrive.
So the high HT on the plates is not nearly so much of an issue as it would be for eg an AC15 type circuit.
What rectifier type is the AO43 intended for?
So the high HT on the plates is not nearly so much of an issue as it would be for eg an AC15 type circuit.
What rectifier type is the AO43 intended for?
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Re: Hammond ao-43
Everything that i am seeing is that it uses a 5U4
Re: Hammond ao-43
AO-43 schematic link?
If it also uses EL84 then that's probably the best rectifier to use if re-purposing the power transformer for use with a different EL84 circuit
Use of a GZ34 would greatly increase the VHT, which may then need to be mitigated somehow.
If it also uses EL84 then that's probably the best rectifier to use if re-purposing the power transformer for use with a different EL84 circuit
Use of a GZ34 would greatly increase the VHT, which may then need to be mitigated somehow.
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him!