new panel design and cathode-biased power amp mods

 

This new panel design embodies my recent changes: boost switch, making use of the available extra triode stage now that I'm switching to a cathodyne phase inverter; and output jack, to allow patching the tube preamp into the VTX preamp (or anywhere else), independent of the preamp select switch.

As you can see, most of the wires I'll need to access, to attach the new circuitry, are available on this 6L6 power tube board.  And this will be the only board that I need to modify, as shown.

BTW, notice that, the way they have things connected, you definitely cannot run 7027 tubes in this amp.  These are functionally the same as 6L6s, but they have two of the octal pins which the 6L6s don't use (pins 1 and 6), connected redundantly to other pins.  The way Peavey has the sockets wired would short the cathode to two of the grids in a 7027.  Not sure why they did this, other than for mechanical stability and without thinking of the 7027.

I won't have to attach anything to the VTX preamp board, which is nice because that one mounts with the traces facing downward, totally inaccessible.  The single-sided tube board has all the traces on top.  That's especially helpful since Peavey have chosen to *rivet* the tube sockets to the chassis, making it darn near impossible to remove or service this board.  Yikes!  I hope the tube sockets never need replacing.  If they ever do, you'll see me connecting them with wires to this board (or a different board), and attaching everything with screws.  C'mon, Peavey!

I'll have to pick up a couple of other wires from other places: such as, VTX preamp output, negative feedback line, and footswitch signals from jacks on the back panel, and +15VDC from the power supply board.

(Actually, turns out I don't need to cut the wires shown in the diagram above; simply leaving the connector unplugged, which would normally plug into the preamp board, accomplishes the same thing.  The only physical change needed is to cut the one trace where shown, thus separating the inputs for the two pairs of 6L6s in the push-pull topology.  Then, I will use existing component solder pads to attach the cathode-bias resistors and capacitors, without having to disturb the board solder mask any further.)