The 12BY7s were gassy, they would stop oscillating and cause the 6146 to sit at zero bias!!
I didn't have any 12BY7s around but I scrounged and found a pair of 6HB6s. Their pinouts are almost identical to the 12BY7s.
The filament feed was cut from pin 6. The jumper from pins 4 to 5 was cut. Pin 4 was left as is, the wiring from pin 6 (filament power + small capacitor) was then tied to pin 5. Pin 6 was left alone then.
Then in the oscillator, it was necessary to do a few things:
1) Screen grid feed. Remove the stock 27k resistor that ties the screen to B+. Don't discard the resistor, save it for the next step.
2) Make a voltage divider, 27k to ground, 82k to the B+ where the original 27k screen resistor was attached.
3) At the junction of this voltage divider where 27k meets 82k, tie 100k to the screen grid.
4) Add 100pF in series with the control grid.
5) Put 680 Ohm in series with the Cathode (but leave the stock bypass cap alone).
That was it. The DX-35 can now run with 6HB6s instead of 12BY7s.
