Component List

Resistors:

R1 = 68 k, 2 W

R2, R3 = 560 Ω

Capacitor:

C1 = 22 µ / 200 V, electrolytic

Semiconductors:

D1..D4 = 1N4004

D5..D7 = 33 V Z diode, 1.3 W

LED1 = LED, yellow, 5 mm

T1 = NPN transistor, V_CE ≥ 200 V, e.g. TIP50

IC1 = TL431

Miscellaneous:

S1, S2 = 1 A / 230 VAC SP switch

S3 = 1 A / 230 VAC push button

M1 = DVM module 3 or 2.5 digits, range 100 V

Tr1 = 90 V sec. transformer (see text)

Heat sink for T1

2 sockets, 4 mm