Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Noob Help: Converting Thomas organ / Wiring
Noob Help: Converting Thomas organ / Wiring
Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 12th December 2010, 04:49 PM   #1
Skullface is offline Skullface
diyAudio Member
Join Date: Dec 2010
Location: NJ
Talking 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
  Reply With Quote
Old 12th December 2010, 06:15 PM   #2
VictoriaGuy is offline VictoriaGuy  Canada
diyAudio Member
Join Date: Dec 2008
Location: Victoria, BC
Noob Help: Converting Thomas organ / Wiring
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.


Last edited by VictoriaGuy; 12th December 2010 at 06:21 PM.
  Reply With Quote
Old 15th December 2010, 12:30 AM   #3
Skullface is offline Skullface
diyAudio Member
Join Date: Dec 2010
Location: NJ
Default 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.
  Reply With Quote
Old 10th March 2011, 09:56 PM   #4
luckyz2 is offline luckyz2
diyAudio Member
Join Date: Mar 2011
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.
  Reply With Quote


Noob Help: Converting Thomas organ / WiringHide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
converting Baldwin organ amp to guitar PRNDL Instruments and Amps 18 20th September 2011 06:21 AM
Noob amp wiring question... Tube Noob Tubes / Valves 5 22nd March 2008 03:43 PM
Help needed for Thomas 1541 DAC's DUC985 Digital Source 0 20th October 2006 02:44 PM
Thomas Sheu Magura Analogue Source 15 2nd September 2006 04:55 AM
Converting Tube Organ Amplifier xlh1000 Everything Else 0 18th July 2006 06:22 PM

New To Site? Need Help?

All times are GMT. The time now is 04:17 PM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio