Posted on Leave a comment

Handmade analog Icom CR-282. For IC-706MK2G

1. TL431 
2. Two resistors 300 Оhм, 1 wt. 
3. Thermoresistor 10коhм 
4. Resistor 10 кhом 
and thats all.
TL431 is an adjustable zener diode, with an allowable current of 100 mA.
so … we don’t need anything else.
the circuit is very simple.

resistors R3, R4 and thermistor must have thermal contact with the quartz resonator case. (pressed through thermal paste)

you may have to choose a resistor R1 to achieve a stabilization temperature of 50-60 degrees.

The scheme works as follows.
when voltage is applied, a current of about 80-90 mA flows through an open zener diode and heating resistors R3, R4, which causes heating of the resistors and the case of the quartz generator.

As the temperature heats up and approaches the working temperature, the resistance of the thermistor decreases, which leads to a smooth closing of the zener diode … and a decrease in the current through the heating resistors .. the system comes to equilibrium .. The heat outflow is compensated by a small current through the heater, which is automatically maintained at the desired level so that the temperature remains stable.
The temperature of the quartz generator case is maintained with very high stability .. not worse than 0.5 С °

the board is installed in the regular place of CR-282, right on top of the native quartz.

author R6CDU

Leave a Reply