Hello Tom!
On 13 Jan 98, Tom Scioscia wrote to Rich Lockyer:
 TS>        Do any of you guys have the schematic for the Blackface Dual
 TS> Showman?
Nope.
 TS> Also, do you have the dimensions for a Marshall 4x12 slant?
No, but there's plenty of guys here who own them.
 TS> Also,
 TS> think I should use Carvin Vintage 12s or the British 12s?
Tom used the Vintage 12s in his Marshall 212 cabinet and they sound great.  I 
haven't heard the BR series so I can't tell you how they sound.
 TS> Actually, which
 TS> would be the closest to Peavey Sheffeilds,
Never heard them.
 TS> The
 TS> Peavey cabs are basically Marshall dimensions, right?
I wouldn't count on it.
 TS> And can I order
 TS> Sheffeilds from Peavey?
Possibly.
 TS> Also, where can I get the boards for the
 TS> point-to-point wiring?
I haven't seen them, but you might try AES.
 TS> I plan on doing this just like the real thing and
 TS> that's basically the only thing I'll probably have trouble getting.
One of the problems that I can see is mounting the board.  These were 
basically a heavy cardboard board with eyelets along the edges for tiepoints. 
 My preferred method is to simply use terminal strips... the kind with 12 or 
so lugs with an "L" bracket or two on the bottom for mounting:
                 _   _   _   _   _   _   _   _   _   _   _   _
                |O|_|O|_|O|_|O|_|O|_|O|_|O|_|O|_|O|_|O|_|O|_|O|
                |_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|
                    |_|                                 |_|
Just don't forget which two are grounded!
 TS> Oh, about the transformers,
 TS> what are the specs on what I'll need for a Dual Showman? Unless it's
 TS> already there in the schem,
The primary impedance of the output transformer is determined by the number 
and type of output tubes.  Of course, the wattage is determined by the output 
tubes and B+ level, plus whatever safety margin you feel comfortable with and 
can afford.
The power transformer is where you can play around a bit.  Even the blackface 
Fenders tended to run the tubes a little hard, so lowering the B+ is not a 
bad idea.  The secondary voltage should be on the schematic.  If not, 
reverse-engineer from your desired B+ level, and don't forget to allow for a 
loss of about 40v through the rectifier (10v for solid state).
 TS> I'm going to put a switch coming from the
 TS> output tranny to switch speaker impedances.
Depending on the transformer, that may not be easy.  The Hammond PT series 
transformers use a bucking coil.  I was able to wire one with an impedance 
selector switch, but it required a 4-pole 3-position rotary switch and I had 
to use all four poles, in addition to a couple of hours figuring out how to 
wire it.
C-ya! Rich
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