[450] IC-207H repair

[K1FSY]

indeed it was and it is now working again

On 10/27/2015 7:14 PM, John Foege 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
> <mailto: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
> 
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