T1 = 115/10 VAC transformer. Center Tap (ct) not needed.
IC1 = uA723, LM723, or equivalent.
Q1 = 2N3055, NTE130, or substitute. (TO-3 case) Mount on a coolrib!
BR1 = 80V-5A (or better)
R1 = 0.56 Ohm, 1 Watt, wire-wound type, 5%
R2 = 750 Ohm, 5%
R3 = 2K7 (2700 ohm)
P1 = potentiometer, 1K, Linear
C1 = 2200uF, 35V
C2 = 470pF
A parts kit (no pcb) is available: [Click Here]
C1 filters the noise and spikes off the AC. Adjust the circuit for 9V or 12V output voltage, or whatever voltage level your pc mini drill
is using, with the P1 potentiometer.
Q1 can also be a MJ2955 in a TO-3 case.
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Copyright © 1995 - Tony van Roon