ampeg vt 40 schematic ??? more than one? &n

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gammelnalle
Junior tube assistant
Posts: 11
(2/18/04 4:03 pm)
 ampeg vt 40 schematic ??? more than one?
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 Some years ago I got an old beaten up chassie. No tubes, no box, broken PCB etc etc....
Stamped on the back panel it says VT 40....
BUT the schematic I found don't match at all....
Mine has 5 preamp tube (at least holders... ) AND one PI
I've tried to sketch the schematic down, but too many loose ends...
The input is a 5,6M resistor.!!!!
The "thing" that looks lika a ceramic cap , and on the schematic i've found looks to be a coil with 4 legs... but mine has 7 legs!!! etc etc...

The whole amp must be totally dissolved  , no problem, but it would be nice to see what I've got!!

from sweden with love
 
6G6
Junior tube assistant
Posts: 85
(2/18/04 5:02 pm)
 Re: ampeg vt 40 schematic ??? more than one?
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 It sounds like what you've got is a chassis and an opportunity to build something on it.
Does it still have transformers?
That could point you in the direction of what it could become.

If it helps,
www1.korksoft.com/~schem/ampegamps/vt40poweramp.pdf
www1.korksoft.com/~schem/ampegamps/vt40preamp.pdf

Edited by: 6G6 at: 2/18/04 6:45 pm
 
gammelnalle
Junior tube assistant
Posts: 12
(2/19/04 2:37 am)
 Re: ampeg vt 40 schematic ??? more than one?
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 Thanks for reply!!! But Those scematics is the one I,ve found...

Yes the transformers still there, and the powertranny gives something like 550V !!!!!
The OT is looking OK when I mesaure it with an ohm meter, both prim and sec winding....

thanks again

björn
 
6G6
Junior tube assistant
Posts: 86
(2/19/04 12:08 pm)
 Re: ampeg vt 40 schematic ??? more than one?
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 That was the only schematic I could come up with.

Sounds like you can make something of it by going point to point. Since the PCB is broken you don't have much choice.

Next you need to think about what you want to end up with.
550V seems to have been fine for the 7027s, 6550s would be happy with that, I believe EL34s would work, maybe KT66s.
Output trans primary impedence might point you in the direction of one or the other.

If it looks like rebuilding the VT40 just isn't going to happen, you can always build a"generic Fender normal channel" preamp driving a pair of whichever output tubes you deem best suited and at least have a pretty loud, working amp.

Once you get there, you can change things until you are either happy with it or tired of it, whichever comes first.

 
gammelnalle
Junior tube assistant
Posts: 14
(2/19/04 3:15 pm)
 Re: ampeg vt 40 schematic ??? more than one?
--------------------------------------------------------------------------------
 Thanks for your answer!
I guess it'll end up, just like you said, as an Bassman kind of amp.... but more of a Vox.... (AC50) but they are very simalary in the end... the PI is a little bit different...

But again:
Thanks a lot from Sweden

björn
 
 
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