[tacgps] TAC-2 build/test

[Jim Hogan]

I see a recent post regarding an unbuilt TAC-2.  Well, I finally got 
around to building one this weekend that I have had in a box for years.

I have a couple of 1998-vintage Oncore GTs that I got from BG Micro and 
both of these work fine with another interface board 
(http://www.seismicnet.com/gps/index.html) that I got once I figured out 
that the TAPR interface board was discontinued.

That TAC-2 seems to work... mostly.  Test voltages for +/- 10V were more 
like 8.9, but test LED blinks as expected.  

Interesting, TAC-32 recognizes it as a generic NMEA and the red LED symbol 
on TAC-32 blinks in time with the LED on the TAC-2, but there is no NMEA 
output that I can see, nor can the unit be recognized as Motorola binary 
or Motorola NMEA.  Same with WinONCORE, VisualGPS, Hyperterm, etc.  No 
NMEA output.  

So it looks like TAC-32 is seeing 1PPS and that makes it happy enough to
not say "GPS not found" but that's about it.  I am trying to think of what
connection might be amiss that would cause this.  Solder joints look OK.  
One curiousity:  For the Oncore VP/UT (GT?) you need to cut a trace on JP3
and add a jumper to reverse TXD polarity.  I did that buy maybe a bit
messily.  After cutting that trace it looked like I had cut into another
layer and wondered if I had created some new continuity.  Anyhow, that is 
the one possible goof up that I can think of.  

Any other ideas of what I might have messed up?  :)



-- 
-*- Jim Hogan		jimhogan AT drizzle.com
    N7BFD
    Seattle, WA