[TenTec] Argonaut V Intermittent TX - Mea Culpa

[Peter Inskeep]

Hi, Rick,

Congratulations on finding the problem with your Argonaut V transmitter function.  You clearly have learned a lot about what makes the 516 tick.  

I write because my 516 transmitter function went south last weekend.  I should qualify that by saying that the output power on all bands dropped down to about .55 watts, or a little higher on 40 and 30 meters.  I was actually able to make a contact at that power level, which I suppose is what QRP is all about.

I have neither the knowledge, skill or equipment that you have, so don't expect to have much luck troubleshooting the rig.  The answer is most likely to send it back to Ten-Tec for an out-of-warranty repair.  However, I just got my Omni VI Plus back from Ten-Tec's Service Department, and it will be a while before I can assemble the $$$ needed to get the Argonaut V returned to them for repair.

Long story short, as they say.  I wonder if you saw anything in your troubleshooting that would point to the finals being unable to work, while still letting enough RF out of the box to make contacts?  I suppose that the low level drivers still work, or I would not get any output.

The failure occurred while the rig was turned off and not in use.  My guess is that the finals blew, but that did not happen while I was keying the rig.  

I have already taken the covers off once to nose around, but did not see any smoke come out when I opened it up.  I plan to go into it deeper in the next few days.

I know that the answer is the excellent Service Department at Ten-Tec, but I like to see if I can break things worse before asking the pros to fix them.  And I have done innumerable master resets.

Thanks in advance for any thoughts you might have, even if I am unable to follow through and make the repairs.  Glad you have your rig working again.

Also glad that my Argonaut 516 did not fail until the day before my Omni came home!

Pete, NO2D.


Rick Williams <ve7asr at yahoo.com> wrote: 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



      
_______________________________________________
TenTec mailing list
TenTec at contesting.com
http://lists.contesting.com/mailman/listinfo/tentec