WARNING: attempt at own risk!! I will not take responsibility for any damage you may do to your ETX.
Parst List:
SW3 - DPDT switch - added to ETX circuit to determine which power source to use
SW4 - DPDT switch - on/off for drive controller power supply
PB1 - DPDT pushbutton - switch between new circuit and original circuit
PB2 - DPDT momentary pushbutton - TURBO bypass switch - super fast speed
(sorry - I just buy DPDT switches for everything, keeps the options open, eh!)
D1 - red LED - indicators, on/off, and ETX/new circuit - 2 req'd
D2 - silicon diodes - block back current - 2 req'd
R1 - 10K resistor - 2 req'd
R2 - 5K pot
R3 - 1K resistor
R4 - 1.3K resistor
Adjustable Power Regulator IC - LM317T - radio shack part # 276-1778