Working Principle of Zone Selector Circuit

The zone selector circuit consists of transistor V, diode VD, thyristor VTl-VW, control button Sl-S4, sound source indicator light emitting diode VLl-VL4, relay Kl-K4, resistor Rl, and sound source input socket XSI-XS8.

Turn on the + l5V power supply. When the Sl-S4 is not pressed, the transistor V turns on and provides the working voltage for the zone selector Kl-K4. However, because the crystal tube VTl-VW is in the cut-off state due to the absence of trigger signal, the Kl-K4 is not suction, the VL1-VL4 is not bright, the open contacts of relays are disconnected, and the OUT has no voice source output.

When SI is pressed, V is cut off. +l5V voltage is charged by Rl and SL. When Sl is loosened, V is turned on, VTl is triggered by charging charge on Cl, Kl is absorbed, VLl is lighted, and the audio signal output by TUNER is output to power amplifier through two groups of Kl's open contacts.

If you need to select the CD signal, you should press S4 and then release it to make VT4 turn on, K4 absorb, VM light up, indicating that the selected sound source signal is CD signal. When uranium is pressed, VTl is cut off, Kl is released and VLl is extinguished.

Zone Selector Component Selection

Rl and R2 use 1/4W or 1/8W carbon film resistors.

Aluminum electrolytic capacitors with 16V withstand voltage are selected for Cl-C4.

VD uses lN4001 or 1N4007 silicon rectifier diodes.

VLl-VL4 uses light emitting diodes of different colours of 3 or 5 mm.

V uses silicon NPN transistors of S9014, C8050 and 3D Gl2.

MCRlO0-6 crystal division tubes are used in VTl-VT4.

Kl-K4 uses small l2V DC relays with two sets of control contacts.

S1-S4 all use micro-motion button.