Hammond AO 37 amp used for parts

[Mongrel714]

Hello new guy here, I've been wanting to build an amp for awhile now, and I realize the Hammond AO 37 is not an easy amp to convert, but it has some great doner parts and I have access to a metal shop to modify the chassis to be useable. I just want to try a simple build first, later on the Marshall clone kit.
I've got a large transformer, schematic says 310v+ three smaller transformers, numerous 9 pin sockets, two EL84 sockets, 4 eyelet boards, anyway, a lot to start with, was thinking of a 18w Marshall style or a Karman Ghia style, either way I will need some guidance! Thanks in advance. I'll have to take some pics with my camera as my phone saves a weird photo file

[Mongrel714]

[https://postimg.cc/DWZNNg0M
[https://postimg.cc/S2mf5QDP
[https://postimg.cc/4YZypKdj]

[Mongrel714]

I've learned the tube next to the power transformer is a rectifier tube. a 5Q4GB, if anyone has a build thread or a way forward from here it would be greatly appreciated, I'm a newb and this is a learning experience for me, that being said, Ive heard some great sounding guitar amps built on Hammond platforms, I realize this amp is not going to be the most simple one to try, the amp works, Ive had the organ for several years, I hope someone can give me some guidance here! thank you, Aaron

[Mongrel714]

PS, I have the schematics on this.

[JMPGuitars]

Search this site for Hammond amp conversions and you'll find more info.

Thanks,
Josh

[Mongrel714]

Here they are.
[imghttps://i.postimg.cc/9Frhh6cb/Pre-amp-power-supply.jpg][/img]

[Mongrel714]

Hello! I have been working on my little project, I have it stripped, cut down the chassis, fit the power and output transformers, the rest is just place holders trying to figure what should go where, I found a Fender style build, but I would rather do a Plexi type amp, just need to be steered toward the right schematics, let me know if any one can point the way!! Thanks all

[Mongrel714]

Forgot the pic
[https://postimg.cc/jnQYn2Vn]

[Mongrel714]

Hey guys, This is the build I've settled on, running through start up steps and seems Im getting 460 VDC on the board, Bias resistors, On pin 2 of the EL84s (Control grid?) , some how I feel thats a little high
Im using the Hammond organ Transformers, power and output, any suggestions, or what info do you need? Thank you.

[Mongrel714]

Oh, and the current limiter was not lighting up???

[Mongrel714]

So far The voltages I recorded are:
B+
1-403
2-368
3-335
4-331
EL84
plate-403
grid-41
screen-369
Im being cautious going forward not knowing if the voltages over 400 are too high, hope some one can help out with a little guidance! Thank you.

[Bieworm]

Although some will disagree, but plate voltages exceeding 360VDC is like dancing on a rope with modern days EL84 tubes. They are NOT like the Philips / Mullards from the olden days.
Also, why take the risk? One can easily yield decent volumes with more conservative plate voltages. The main reason for even using EL84’s is their excellent and complex overdrive properties that are hard to beat by using other types of tubes. There are much better choices out there for yielding clean headroom and reliability.

My 2cts

[Iain T]

There are much better choices out there for yielding clean headroom and reliability.

I'm just going through some iterations on my Princeton build (6V6 not EL84 of course) and this is both simple and nuanced! Current steps - increase PI B+ but, before that, upgrade the OT!

More real-world volume is often better achieved with something like a more efficient speaker as well as many changes to up output of the amp will change key characteristics!

[Bieworm]

There are much better choices out there for yielding clean headroom and reliability.

I'm just going through some iterations on my Princeton build (6V6 not EL84 of course) and this is both simple and nuanced! Current steps - increase PI B+ but, before that, upgrade the OT!

More real-world volume is often better achieved with something like a more efficient speaker as well as many changes to up output of the amp will change key characteristics!

True.. but there is no “better” or “worse” tone. If you end up liking it, that’s most of the time good enough and worth the effort.

[Iain T]

True.. but there is no “better” or “worse” tone. If you end up liking it, that’s most of the time good enough and worth the effort.

Yeah, if it sounds good... it's good!