[450] IC-207H repair

[John Foege]

And because Google translate is garbage, I will translate this line,
because it's the key line:

Vermutlich durch unterschiedliche Ausdehnungskoeffizienten zwischen Keramik
und Kühlkörper treten im Keramiksubstrat feine Risse auf, die mit dem Auge
nur mühsam zu erkennen sind. Irgendwann führt das dann auch zu
Unterbrechungen in den aufgedruckten Leiterbahnen, bei mir gleich an sechs
verschiedenen Stellen.

Presumably, fine cracks occur, which are only with great effort visible to
the naked eye, due to the different thermal coefficient of expansion
between ceramic and heatsink material. With time, this leads to cracking in
the printed circuit board traces as well, which in my case, was present at
six different places.

On Tue, Oct 27, 2015 at 7:14 PM, John Foege <john.foege at gmail.com> wrote:

> Vermutlich durch unterschiedliche Ausdehnungskoeffizienten zwischen
> Keramik und Kühlkörper treten im Keramiksubstrat feine Risse auf, die mit
> dem Auge nur mühsam zu erkennen sind. Irgendwann führt das dann auch zu
> Unterbrechungen in den aufgedruckten Leiterbahnen, bei mir gleich an sechs
> verschiedenen Stellen.
>
> This is, indeed, exactly what I had guessed the problem to be when talking
> it over with Bill while you were off the air earlier. I told Bill, that in
> my opinion, most likely it was the repeated thermal cycling of heating and
> cooling that lead to cracks in traces on the power module. Looks like I was
> right !! Really a very common mode of failure. If you were a long-keyer,
> which you are not, I would have said de-soldered itself. But knowing that
> you don't key long, I figured cracked traces from thermal cycling.
>
> On Tue, Oct 27, 2015 at 6:57 PM, K1FSY <k1fsy at vhfwiki.com> wrote:
>
>> I was having intermittent power output problems with the IC-207H I
>> received in trade from K1MAL. Noticed 35w power output on 2 meters which
>> was reduced and then no output. After opening it up and desoldering the
>> antenna connector to get the board out I did some troubleshooting in the
>> APC circuit because the internet said it was a common fail point,
>> however it shares the same APC circuit for both vhf and uhf and the 70cm
>> side worked fine. Desoldered the PA module and popped off the plastic
>> cover as per this page that john will appreciate, and sure enough the
>> thing had microfractures in the ceramic board. Instead of going crazy
>> with tiny wires I just added a little solder and reflowed the traces
>> that the cracks were running under and buttoned it back up. Apparently
>> Icom didn't bother putting heatsink compound on the bottom of the
>> modules and just screwed them to the board, so eventually they heat up
>> too much and snap crackle pop.
>>
>> http://www.dk7in.de/TM733.html
>>
>> _______________________________________________
>> 450 mailing list
>> 450 at lists.vhfwiki.com
>> http://lists.vhfwiki.com/cgi-bin/mailman/listinfo/450
>>
>
>
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