Heat Sinks for My IC-706 MkII

This article appears in the September issue of World Radio magazine with another name although it is mine. I held off putting it here in June at the magazine's request. I will send pictures to you as you request rather than post them here since they take up a lot of space. Request them by writing to me at sirdrakejr at aol dot com. Since credit was not given to me, here is the article as I sent it with the original title:

This is an article describing an external modification I made to my Icom IC-706 MkII. It may also apply to any radio where the heat buildup seems to be high. Mine was killed by heat even though Icom said the internal heat would not do it. I have been a member of the HF Pack group for quite a while but never put the radio into one of those backpacks out of concern for the amount of heat it generated. This little radio generated a LOT of heat! I called Icom and asked them about the heat and what would happen if the radio was placed in a closed environment like a backpack. They told me nothing would happen and the heat was not enough to affect the operation of the radio since it had a fan that automatically came on to cool the inside. Even with that assurance, I did not put it to use in a backpack. I instead used aluminum material to convert the radio to travel and also act as a heat sink on the sides of the radio. It evidently wasn't enough. Heat killed my radio. It was hot to touch and fried. I sent it to the factory and they replaced the necessary components to fix it. The tech told me one of the internal resistors was hot enough to burn him. I paid my money and wondered what to do to keep it from frying again. This article will tell you what I did.

The first thing I did was replace the radio with my third in the series of IC-706 radios, the "G" model. Now if the MkII dies, I will still be on the air. The next thing I did was figure a way to protect the radio from the internal heat it generates. I know it has a fan and it ran a lot. It didn't keep it from getting killed by the heat. I needed to do more. I measured the surfaces available on the outside of the radio and wondered if it would be possible to place heat sinks on it to draw the heat from the radio even if the fan failed. I perused the number of catalogues I get and found just the item I needed at All Electronics Corp (http://www.allelectronics.com/). They had used heat sinks for sale that were just the right size to put six of them on the top of the radio and draw that heat off. See picture number 1 of the individual heat sink I used.

The heat sinks were from computer usage and had a lip that needed to be filed off to mount them flat on the radio. I also needed to figure a way to mount them and allow me to get the screws that hold the top cover to the radio. My Dremel tool came in handy for that little task. I laid the heat sinks out on the radio cover and cut and ground each one where it needed it in order to allow access the screws. The heat sinks covered the top of the radio perfectly.

Next I had to bolt the heat sinks to the cover so the heat transfer would be sufficient to do the job. The cover sits about one quarter inch above the board in the radio. There are also some spring fingers that ground the cover to the internal boards as well. The heat sinks will also sit above the internal divider that separates the final board from the front end. That space was too small to allow for bolting the heat sink to the cover unless I moved the bolts off center a little. I needed to allow for all that when I drilled holes for the mounting screws. I drilled the holes as close to center as I could and still miss all the stuff I needed to miss. The six heat sinks would cover five cover screws either completely or partially and I needed to make notches and a hole for them in the heat sinks. I did all that and bolted the heat sinks to the cover. I ground off the extra threads of the bolts I used to hold the heat sinks and smoothed them out so when this goes into a backpack, the threads wont tear the insides of the backpack.

The final mounting looked pretty good but needed something more. It needed to be painted so it looked good. I first thoroughly cleaned the heat sinks with acetone. Knowing the amount of heat that could be generated by this radio, I bought some flat black barbecue spray paint to paint the heat sinks. The final outcome looks good and when the radio is on now, I feel almost no heat from the cover of the radio. I have had the radio on for hours and the fan still has not come on. It may be that the Icom repair job took care of the original problem or the heat sinks are doing what I hoped they would do. At any rate when I finally take it out in a backpack I feel much more comfortable knowing the heat won't stay in the radio where it has proven to be a killer, whether or not the fan comes on. HFPack group here I come; finally. And I will be cool too.

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