[450] IC-207H repair

[John Foege]

Solder is a better idea...it's going to handle the current better and also
not be overly inductive.

On Tue, Oct 27, 2015 at 7:22 PM, K1FSY <k1fsy at vhfwiki.com> wrote:

> google translate did good for me i got all that out of it when i read
> through it the first time. My cracks were in pretty much exactly the
> same place as his too.
>
> I was going to try using shield wires cause i have a mess of them handy
> but i said screw it and just added and reflowed the solder.
>
> On 10/27/2015 7:21 PM, John Foege wrote:
> > 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
> > <mailto: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
> >     <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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> >         http://lists.vhfwiki.com/cgi-bin/mailman/listinfo/450
> >
> >
> >
> >
> >
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> >
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