Error fix: Pin 7 and 2 were reversed. Original pinout was correct.
R1 = 10K
R2 = 100K
R3 = 100 ohm
R4 = 50K potmeter, Linear
C1,C2 = 0.1uF
C3 = 0.01uF
C4 = 2700uF
Q1 = TIP41A, NPN, or equivalent
Q2 = TIP42A, PNP, or equivalent
L1 = 1uH
T1 = Filament transformer, your choice
Do the following checks:
1) You have connected the filament transformer in REVERSE yes?
2) If not, disconnect the power and reverse. If you have, disconnect the transformer and measure the voltage after L1 and ground.
3) Just in case, GROUND for this circuit is same as negative (-).
4) Q1/Q2 are oposites, e.i. npn/pnp.
5) Is your 555 perhaps defective? Disconnect R3 from pin 3 and check pin 3for a pulse.
6) Check your transistors to make sure they are not defective.
Copyright 2002 – Tony van Roon