by EWBrown » Sun Nov 14, 2010 2:02 pm
The 6N2P is very close in operating characteristics to 12AX7, (the rp and gm differences are fairly minor, the mu is the same) with the exception of the filament connections being pins 4 and 5 (as with a 6DJ8 or 6CG7). Pin 9 is not used, or it may be an internal shield between the two triode sections.
To modify the Rev D board, the etch connecting pins 4 and 5 must be cut. Otherwise the 6N2P filament will be shorted by the PC board. Also cut the etch (next to the solder pad) for pin 9, and connect pin 9 to a convenient ground on the board (or just leave it open).
Depending on the cut, either pin 4 or pin 5 will be connected to the existing 6.3VAC traces on the board. The other side can then be "stolen" from the cut etch that was previously connected to pin 9, or from the adjacent 12AU7 socket's pin 9. It is imperative to verify your filament voltage connections with a resistance test, using any VOM or DVM, before applying any filament voltage, just in case the wiring ends up as being shorted.
It is actually a lot simpler than it sounds, just be careful and patient.
As the original circuit doesn't have a grid stopper, the 6N2P shouldn't need one, either.
/ed B
Last edited by
EWBrown on Mon Nov 15, 2010 5:46 pm, edited 1 time in total.
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