Crawls Backward (When Alarmed)

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Tweed Super Bandmaster Clone - Circuit Board is Complete!

The board is 98 percent done and ready to go into the chassis.  Just a few connections to the board remain to be done - the 4 inputs.  I'm going to wire the input jacks off the chassis and then wire them to the board before I put it in.

Here's a picture of the board when it was about halfway done.  Look at all those crazy long leads.  They all got snipped and cleaned up.

To the left is the bottom of the finished board.  You can see the 'subterranean' wiring I mentioned in an earlier post.  There is a fair amount of it.

A couple of notes here:  the yellow arrows point to places where I'm using shielded wiring (RG-174).  These are the run from just after the 68K input resistors to the grids of the first preamp tube, a long run from the treble control to the coupling cap going into the grid of the phase inverter tube, and the long run from the coupling caps to the grids of the power tubes.  I'm trying to keep noise down so I went after the most logical places where RF or other noise could be picked up - which is the inputs (grids) on most of the tubes.

At the bottom of the board, you can also see the ground buss I ran for the preamp filter cap, all the shields, and the cathode bypass caps for the preamp section.  That buss will run to a 'preamp' ground on the input side of the amp.  The inputs themselves as well as the tone control grounds will all run there.  The main filter caps and the main chassis ground will be on the opposite end of the amp near the power transformer.  Nothing earth-shattering here - just good wiring practice to help keep hum and noise to a minimum.

Here's the top of the board.  Pretty much standard Fender fare.  You can see all the flying leads that will go to tubes when it's installed.

I used Mallory 150 capacitors for the preamp section (the yellow caps).  I have these in my Vibrolux clone and they sound great.  They (supposedly) sound like the Astrons that Fender used in original tweed amps.

The coupling cap to the phase inverter is a Sprague 716P Orange Drop.  (Guess which one it is?).  I used it for clarity of tone going to the output section.    

And finally, the output caps are Sprague Vitamin Q paper-in-oil caps from my secret stash.  I used these in my Dynaco PAS rebuild and they sound terrific.  Since the amp's future owner mainly plays jazz and country and prefers a clean tone, I figured the Vitamin Qs would be just the ticket for a detailed, but warm clean tone.  I'm itching to hear this amp now!

Next up will be mounting the hardware - the tube sockets, the transformers, the pots, jacks and switches. That will have to wait until next year!

 
 
 
 

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