Hammond or Everett AO-48 chassis - diyAudio
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Old 29th July 2008, 08:09 PM   #1
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Default Hammond or Everett AO-48 chassis

Hello tube people
I got this organ amp chassis from a nieghbour who found the organ on a bonfire.He told me it was a Hammond.
The next day I rushed to the scene with my trailer to save the organ,but the local kids had completly kicked it to pieces(little tiny pieces!!) and burned the rest.
I am newbie to tubes(some minor experience,I am very aware of the dangers) and I want to make this amp into a guitar practice amp.The only info is the number stamped on the chassis.It says AO-48-1B.
I need schematics.I have searched in vain for days on the net and only reference to it is an Ebay seller who has replacement tube sets for hammonds and stuff.He says it is from an Everett 2022 organ but this has got me no further.
Also heard it might have been a Hammond Chord organ.Still,no luck.Too many models,variants etc..
I know I could just buy a tube amp but money is tight and anyway I would much rather ressurect this old amp from the dead.It seems such a shame to waste.
Has anyone heard of this amp,does anyone recognise it,any ideas where to get schematics?
Any suggestions greatly appreciated.
Here is a pic.
P.S it has 7247,12AX7(x2),6267,6BQ5(x2),6CA4
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Old 20th August 2008, 07:05 PM   #2
m6tt is offline m6tt  United States
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I have one of these that is currently sitting in a chassis as a guitar amp. I had to do a bit of work to get it working. The 6267 is the input pentode, i.e. and ef86. The 12ax7/7025 nearest the el84s is the phase inverter. The 12dw7/7247 is the reverb driver and tremolo oscillator. the other 12ax7/7025 is an intermediary recovery/amp stage. The oscillator's output is not designed (as far as I can tell) to make anything in that chassis oscillate, rather the signal was coupled out through the multi-pin (6 or 7?) plastic connector. It went to a solid state board. The 3-pin plastic connector is for the reverb, the larger resistance across it the more reverb. 1meg-500k is about max. The rca connector labelled "R" (you may have to clean to find this) is the reverb out. The rca connector labelled "G" is the return. The tank should be a 4-8 ohm input with high impedance output. Do not run the amp without the tank, the transformer for the reverb will short and become a flyback inductor for the B+ line (nasty--1.2kv spikes). Under the chassis you should be able to see which RCA couples to the EF86. This is the input. The other two RCAs are perfect for a putting a volume control and tone stack between as this was the foot pedal. It's a great sounding amp, I have mine in an old crate combo chassis with a '59 Jensen P12Q and a customized reverb tank. I redid a bunch of circuitry to get tremolo working. If you have any questions, PM your email address and I'll try to help. This amp will put most ~ 15-20w amps to shame, and it has great tone. Hopefully you have the tubes, they were mostly mullards in mine. The plastic connectors for the two plastic connectors may be hard to find, but I can walk you through hardwiring a different setup. Good luck!
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Old 20th August 2008, 08:33 PM   #3
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Hi m6tt
Thanks for your detailed reply.This info is in-valuable to me.
I am trying to buy schematics from Jerry Welch at the organ service company,but they take a long time to reply to my mails,so I have resorted to drawing the circuit out myself.
Do you know what model organ your amp came from?
I would love to write more but I gotta be up early for work though I will contact you in the next few days.
Thanks again for the info.
My e-mail is aidan17@rocketmail.com.
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Old 20th August 2008, 10:55 PM   #4
m6tt is offline m6tt  United States
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I sent you an email, mine was from the same organ or very similar (everett 3000 and 2000 models are identical except for the solid state portions and number of keys etc. Poweramp is the same as far as I know.)
Good luck, that chassis is a gem!
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Old 21st August 2008, 08:11 PM   #5
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Ok m6tt
I will buy Everett 2000 schematics tonight.
Thanks for the advice.
When I get it repaired I will pick your brains for tips on making this into a guitar amp.
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Old 21st August 2008, 08:28 PM   #6
m6tt is offline m6tt  United States
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here's more info on the reverb tank for anyone that finds one of these:


>The information that I have for an old Gibbs reverb with the letter R is it would be >the same as an Accutronics model 4AB2C1F. I also have info on a Hammond part >number 121-000020 without a clamp with the letter R showing as an Accutronics >model 4AB1C1F. And at the time the letters were the same for different delay times >and mounting planes. So to answer your question on input and output impedances >the models have an input impedance @ 1KHz +-10% of 8 ohms or .8 ohms dc >resistance +-10%. The output impedance @1KHz +-10% is 2250 ohms or 200 >ohms +-10%.
>Regards,
>Cal Shuett - SEPI-GROUP

essentially a fender style tank.
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Old 22nd January 2009, 06:17 PM   #7
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Has anyone managed to find a schematic for this model yet? I would love to see a copy.
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Old 23rd January 2009, 08:16 PM   #8
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Hey Oneroomstudio
I have full drawings for the whole organ including the PSU/Power amp.I am currently modding one of these.
I sent you a mail.Not sure if it sent.Mail me.
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Old 27th January 2012, 03:05 AM   #9
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Default Everett AO-48 power amp

Hi all. Been reading this forum for years, but this is my first post. Trying to revive this thread in hopes someone can PM or email me a schematic for the Everett AO-48 power amp. I have a couple and want to try to convert one to a guitar amp without completely gutting it. Sure hope someone still has this stuff. Thanks a mil!
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Old 16th February 2012, 06:52 PM   #10
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i have one of these organs,mint,sitting in my hallway,is it valuable,should i take it apart?
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