Modification of fan connection for ICOM 756PRO3

In my Icom, I modified the power supply of the fan according to Karsten Brinck – OZ1DB. This adjustment will cause it, that when receiving, the fan rotates at low speed. He didn't turn without this adjustment. I was not happy with the feature, because these low fan speeds varied according to the supply voltage. In addition, if I set the minimum speed at 13.8V by selecting a zener diode, so at 13V the fan did not spin at all. Therefore, I replaced the zener diode with the LM78L05 stabilizer. The diode is Schottky, only due to low voltage drop. In my case, is 4.7V on the fan in the entire range of supply voltages. The fan spins reliably and is very quiet. If you need to set a higher voltage for the fan, use the dashed variable resistance, measure it and replace with solid resistance.

This modification does not affect the original function of the control circuit, this means that when the transceiver is transmitted or overheated, the fan receives full voltage and has maximum speed.

You can access the controller after removing the upper black cover, then the gray shield plate with the loudspeaker must be removed. The controller circuits are on the far left when viewed from the front. Good luck.

Dodo, OM1AVL