• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Noob Help: Converting Thomas organ / Wiring

Hey all - I've been messing with Electronics for a bit now, and when a friend found an old Thomas organ and decided to make a bass or guitar amp out of it I decided to help. So right now I am trying to learn the basics of tube amps, but in the mean time I would like to make sure this thing still works.
It worked when we first plugged it in, but the keys were destroyed. My friend ripped it apart and left me with a mess.

Anyone that can point me in the right direction regarding wiring?

It's an old Thomas model CA Tone Cab out of a Model 21 Organ.
The speaker wire broke off and I'm not sure from where, and he cut the wires to the sound generator portion. I have 3 wires which are not connected to anything now.
And can I just plug something into the Input jack on the AMP itself to test it?
The Project/Mess is online here:
Converting A Thomas Tube Amp to a Guitar Amp | http://skullfacesworld.com

Sorry for the newbie question, but any help at all would be wonderful. Thanks
 
I had a look at your blog and your plan to 'trace the wiring' is the correct one.
You seem to be concentrating on the 'control board' end of the amp.
If it were my project, I'd start with the power supply and work my way toward the input. Identify the wiring on the power transformer and go from there.
Try to find a schematic. Failing that, get a bunch of guitar amp schematics from schematic heaven and compare with your amp. Draw a schematic of your amp. Searching for push-pull tube amp schematics and info will help you . Your amp uses 6V6? tubes in PP?
A lot of old amps like yours had a jack for connecting to a sub-chassis, or to the power switch, so keep that in mind when drawing your schematic.
Don't just try to plug it in unless you are sure what you are doing.
The high voltage DC in that amp can kill.
Make sure you have a power switch, fuse and a proper 3-wire AC connection for a start.
Look at the output transformer connections and you will figure out where to connect the speaker. Again- use a proper jack for your speaker connection.

John
 
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Thanks you for the reply

Spent the last couple of days reading up on all the tubes and the output transformer. Wish I could find the exact one I have. I have no intention of pluging it in for awhile yet, and I've read the various safety instructions.

I'm still drawing out all the wiring connections, and this may sound like a dumb question, but do I need to remove all of the unused connections?
The organ had a pedal clavier which was connected to a 6 prong socket. Does that have to go?
Sorry to be a bother, but it will help me with the wiring schematic as well as learning. Looking at that mess of resistors and capacitors it amazes me this thing works, so of course I'm curious to understand more. Thank you.
 

luckyz2

Member
2011-03-10 10:45 pm
Hi, I am another Noob to say the least. I've started getting into tube amps. And I found your site more than helpful. I recently managed to get an old Thomas GP that appears to have the identical amp. I am in the process of making it into a guitar amp. The organ was in working condition. I hope to have some pictures soon. I should be able to help you out with some of the wires that you had unattached. I will post them as soon as I get to them (it's still a little too cold out in the garage to get to it right now). will be in touch.