Subject: Icom IC-706MKIIG Fan Mode
Unlike the 706, the 706MKIIG do not keep its
internal blower running in receive mode. So, the radio becomes very hot after
half-hour or more
of operation, especially in summer.
A small 200 ohms 1 watt 1% metal-film resistor
connected in the PA board, between the switched +14v and the blower positive
make it run very quietly, dropping the external body temperature of the MKIIG very near to that found in the 706.
The voltage applied by the resistor over the cooler is 4.7 volts and it is sufficient to start and keep it running without any perceptible noise.
Resist to temptation of increase the receive-mode
blower speed (reducing the resistor ohmic value) avoiding to transform your
radio in a
After this modification, the measured radio body temperature after two hours of receive-only mode was 37 at room temperature of 25 ºC
This mod will not alter the transmit behavior of
the ventilation system that will remain operating as usual or even better
46.5 mA auxiliary current supplied by this resistor will keep the blower drive transistor more cooler.
Another benefit is the reduced frequency drift in the VHF and UHF bands, SSB mode*.
One of the resistor lead is connected to the positive of the blower connector and the other in the RF choke (L613) loop as show in the pictures.
If you want added security, provide some
isolation on the resistor leads. DO NOT short circuit the choke winding and be
very careful when
soldering the resistor lead over the male PC connector pin.
In this mod, there is no necessity of board
removal and could be done in a matter of minutes. Only the radio bottom cover
must be removed
Mods are at your own risk - Modifikationen auf eigenes Risiko