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Re: 2.6 FODTRACK Board Questions



I replied, but I think off list.  If you are building the circuit
without the PC board, make sure you use a new schematic.  It says in
the newer FODtrack manuals (>2.4 I think) that there was an error in the 
schematic that one of the comparator inputs was backwards (+ to -, - to + on 
the opamp).  This causes this oscillation.  If you are using the FAR board, 
you will be ok.  I've also heard that the type of transistor you use the 
replace the European NPN in the actual rotor switching can be somewhat 
critical.

Fred W0FMS


>From: "Rich Dailey, KA8OKH" <okh.npi@gte.net>
>To: amsat-bb@AMSAT.Org
>Subject: [amsat-bb] 2.6 FODTRACK Board Questions
>Date: Sat, 09 Jun 2001 16:06:29 +0100
>
>There was a post a while back that addressed a problem of rotor
>"oscillation" -
>
> >"Den Spiess" <dspiess@t-3.cc> wrote:
> >Date: Sun, 3 Jun 2001 05:44:01 -0400
>
> >I just made the FODTracker board to control a G-5400. Currently just 
>using
> >the FODTrack 2.6 software to 'test' the circuit.
> >The azimuth rotor moves to the correct position the oscillates back and
> >forth about 5 degrees. The elevation side works OK.
> >The board looks like everything is in place. Switching the rotors gives 
>the
> >same response using the elevation rotor on the azimuth side.
> >Anyone have any ideas or has seen this?
>
>I don't remember seeing a reply to this query,  but there is an adjustment
>that can be made as per the documentation.  It requires adjusting the
>"dead zone" by changing the value of a particular pair of 1 megaohm
>resistors.
>   There are 4 of these resistors in the circuit (located at U2A and U2B).
>My question is, which ones change the gain, or "dead one"?
>
>I'm about to construct a couple of these boards (from FAR Circuits),
>and I'm sure I'll run into this "anomaly" - I always seem to find these
>problems (or they seem to find me) :-)
>
>tu de Rich
>
>
>-------------
>Rich Dailey, KA8OKH - Phyllis Dailey, KB4NPI
>http://home1.gte.net/web22jfw/
>-------------
>----
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