[TenTec] Argonaut V Intermittent TX - Mea Culpa

[Rick Williams]

Well the 516 TX went "south" again the other day. 
Today it was still not transmitting and I got the
scope out.  I looked at the output of U29A (accessible
on the TX board 8-pin header) and was soon convinced
that the problem was definitely on the Logic board.

The only time I had looked at the Logic Board was to
do the 1.08 firmware mod in December of 2004.  (This
was prior to Ten-Tec issuing the mod and instructions
on how to access the bottom of the logic board.) 
Examination of the 3-component MIC mod indicated that
the only part of the circuit common to all modes was
R212 (I believe this adjusts the minimum TX output of
the 516).

So I dug into the 516 and looked at the "fly-spec" SMT
called R212.  It didn't look right.  I checked the
solder pads on U29A and they showed an open where R212
was supposed to be?  I got out the soldering iron and
put some heat on the part of R212 nearest the rear of
the rig and presto it fell off the board.

It looks like whoever did the mod (oops ... that would
be me) never REALLY got enough heat/solder to the
other end of R212.  Why it took 3.5 years to go
intermittent - who knows.  I resoldered and this time
I triple checked my installation.

At least a failure of R212 makes sense and provides a
logical explanation as to why the TX disappeared. 
Hopefully the mystery is now solved and the problem is
cured.  Again - time will tell.

73, Rick
VE7TK