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Thomas Vox help request

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9/29/2004 9:17 PM

Thomas Vox help request

I'm soon going to be able to think about amps again, and I'd like to renew a long standing mania of mine - the Thomas Organ solid state Vox amplifiers.

Yes, yes, I know, I know; they're solid state, they're junk, sound bad, stink worse. I've heard it all before. Leave me my little perversities.

For my own reasons, I need to locate **dead** driver transformers for these amps. I want to dissect the corpses and figure out how to make new corpse... er... replacements.

So - can anyone help me? Do you know where a dead (or otherwise low cost or free) driver transformer for the Beatle, Royal Guardsman, Buckingham, Berkeley, Viscount, Sovereign or Westminister can be found?? The favor will someday be returned in the form of a winding manual for replacing the beasts.

Please send replies to me at k.e.e.n.@.g.e.o.f.e.x...c.o.m.

9/30/2004 5:35 AM
SpeedRacer	nuthin' wrong with the SS beasties.. story is the whole first Tom Petty album was recorded with them. Plenty of tasty tones there.. then again Mike Cambell could probably make a rubber band on a stick sound killer.. if I come across any of these things, i'll send them down. gd lk!

9/30/2004 9:26 AM
MBSetzer	I did manage to acquire a Defiant which apparently a previous technician was not able to repair. Haven't tried to start the restoration yet, when I do you might get some requests from me for assistance, I've already looked at a lot of your material about these amps. If this one has an interstage transformer, maybe it will need to be investigated at the time. Mike

9/30/2004 2:17 PM

Hi, Mike.

The Defiant/Conqueror/Supreme line is a reverse British invasion. Thomas (I think) managed to convince JMI that the future was solid state. Anyway, that's how the schematic to that particular trio of amps reads.

I worked on a Supreme a ways back and modified it to use a standard reverb tank instead of the ceramic phono cartridge based thingie that came stock. In doing so, I looked the power amp over, and its very reminiscent of the Thomas designs - driver transformer and stacked output stage. The Defiant must be similar.

By the way, the D/C/S series is a dream to work on relative to the Thomas Vox stuff. Neat layout on isolated functionally distinct boards, easy to follow wiring.

The trick to most bipolar amps like these is to get the DC voltages right. First, isolate the power supply and get that working correctly. Then start at the power amp, check voltages and get that right, and open the capacitor leading to its input. Feed a signal and see if it works right. When it does, work backwards toward the preamp. This way you never reach a place where something in earlier stages won't let you know if later stages are working.

10/9/2004 3:21 AM

RG.
I finally got a chance to play on an early Westminster that I bought last year and was storing.
This is the 60w model.
I think I know why you like them, what a unique sounding ss amp. I really like it, it seems to have a more organic sound(for lack of better discription) to it than most ss amps I have played and doesn't sound sterile.
I can hear the Tom Petty thing, this amp can nail the "Refugee" rhythm tone dead on.
I have a friend that has tons of parts kicking around and I remember him having a couple of these amps a few years back, maybe he will have some parts.
Regan

11/10/2004 9:41 AM

Hello R.G and Mike,
I also aquired a '67 Defiant and think it's a great amp. The trem is outrageous. Mine had some issues that I was able to correct, thanks to some theory help from net friend Paul Ruby. Mine initially had the output stage only at half power(only one of the two power trannies working). Some hamfisted tech had rigged the trimmers to make this happen. There are also some resistors in the output stage that are likely to be fried and need to be replaced because they are not up to spec.

These amps are relatively easy to work on. One hard thing is that I need to replace an input jack in the clean channel and it's about impossible to get to unless I take apart a lot of the amp.

My reverb also doesn't quite work right, and I'd love to figure out how to get some reverb working on there. I actually did purchase a mono phonograph cartridge but I haven't tried to make it work yet.

I also am planning on making a duplicate of some of the preamp boards and trying them out, because I find that the amp, though it sounds great, doesn't have the same aggressiveness that can be heard on the Beatle records (like Hey Bulldog for instance). Do you think perhaps it could be the filter caps? Is this what would make the amp sound relatively "tired" compared to a new one?

My DC voltages are good though.

I'd like to talk and trade info with y'all, as I have spent a good deal of time inside this amp.

thanks,
Darren

10/16/2004 8:56 AM
gus	R.G. Try here some cool people at this place. http://www.prodigy-pro.com/forum/index.php Look at the transformer meta or any meta in the Meta meta thread.

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