overheating of the icom 706mk2g

[Robert Tripney]

I have had cause for concern about the heat generated by my 706mk2g even in the receive mode.
It appears that the 706mk2 unlike its predesessor the 706 does not keep its internal blower running in the receive mode an as one would guess acts as described.
There is a none" icom" mod to be found on(KB42LL)site Radio Mods Database and manuels.
Hope this may help any one else who may have had cause for concern.

regards Rab Tripney"MM3MMF)

[Robert Tripney]

Rab

Did you modify yours?

Was it difficult?

Can you post a link to the modification?

JOHN
I shall will do the modification at the club thursday.I have spoken toGm4uye about my concers.Seems a simple mod.

http://www.kb2ljj.com/data/icom/ic-706-mk11.htm

Rab (mm3mmf)

[MM0BSM]

http://www.kb2ljj.com/data/icom/ic-706-MKII.htm

Author: Sergio PY1BEK



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 lead will 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 vacuum cleaner...

After this modification, the measured radio body temperature after two hours of receive-only mode was 37 at room temperature of 25 ºC (98.6/77 ºF).

This mod will not alter the transmit behavior of the ventilation system that will remain operating as usual or even better because the 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 (5 screws).

73, Sergio PY1BEK