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Re: Kansas City Tracker Interface

Hi Bob,

I have one question.  When you say the UP output control is always
at ground level, do you mean with power applied to the board or
with power removed from the board.  I am assuming no power
applied.  Please correct me if I am wrong.

Any of the IC's can be replaced so it is fixable.

The first question in the diagnose routine is to determine if your
software recognized rotor movement in the UP / Down directions.
Basically, if you manually move the rotor up or down does your
software indicate it moved.  Since I do not know what you are
using for software, I will reference WISP since that is one of the
packages that I use.  If I manually move my rotors, the display
for the rotor position will move as I manually press the controls.
If you see no movement of these indicators in the software (not
on the rotor control box itself) then the problem is most likely
associated with the ADC0809 chip that performs the analog to
digital conversion.  Also, the rotor control box itself will confirm
if the potentiometers are good by indicating meter movement
on the rotor control box.  If there is no meter movement, then the
rotor controller box or the potentiometers in your rotor could be
a problem.  Of course, I am assuming you are using an analog
feedback rotor system since it was not mentioned.

There are a few versions of the Kansas City Tracker/Tuner board
that I have seen and fixed for some friends.  One has the rotor
control interface that handles up to 300ma with an open collector
output.  The other does not have the rotor controller interface
circuit that is good for handling about 30ma on the output.

The 300ma rotor controller interface uses two separate 75452
dual peripheral drivers.  The 30ma rotor interface uses a 7406
inverting buffer to drive the rotor output for up, down, left, and
right signals.

The quickest way to tell what you have is by looking in the center
of the board.  You will see a 7406 chip with 14 pins located just
to the bottom left of the big ADC0809 chip.  If you look on each 
side of this chip (left and right) and see a 75452 8-pin device
stuffed on the board you have the 300ma rotor interface option
installed.  If these 2 chips are not installed on the board, then
you have the 30ma option.  I have one of each type, so I became
very aware of the difference when I purchased one off the web
second hand.  It is very easy to upgrade a 30ma interface board
to a 300ma interface board by cutting a few traces and installing
the 2 chips along with some diodes and capacitors.

Back to your specific problem.  If your UP control output is always
stuck at ground you could have a shorted protection diode located
near the DB25 connector on the board edge.  This will not pull the
UP control signal to ground level, but it is a good idea to make sure
it is not shorted.  You can find it by tracing the DB25 pin 3 back to
the diode attached to it.  You could probably test it in the circuit,
but to be sure you will need to left one lead of it from the board which
means unsoldering or clipping one lead and test it to see if is good
with an ohm meter or a diode tester.  If it is bad, then replace it.

When you said stuck at ground level, I did not understand if that was
with power applied to the board or not.  So I am assuming no power
is applied at this point.  If not, let me know.

You still need to check some control circuitry on the board.  The
75452 8-pin chip just to the left of the 7406 in the middle of the board
is the device with the output control for the UP signal that goes to the
DB25 connector at pin 3 on the edge of the board.  Pin 5 on this
75452 is the open collector output control.  If you unsolder this pin
from the board and your measurement to ground disappears, then
you need to replace this chip.

If you do not have the 300ma option with the two 75452 devices
installed on the board, then your UP signal will come from the 7406
14-pin chip located in the middle of the board.  Pin 2 on the 7406
controls the UP signal for the 30ma interface.  If you unsolder this pin
from the board and find the ground level signal to disappear, then you
need to replace this chip.

Again, I assumed that you see a ground level measurement on the UP
control line at the DB25 pin connector at pin 3 with no power applied.

I will stop here, before I make too many more assumptions, because the
path to find the trouble starts to go in a few different directions without
knowing any more detail.

Hope this helps in your troubleshooting...

I have never had an ADC0809 go bad on my boards in over 10 years of
almost continuous operation.  I have been lucky, because I have had
several potentiometers in my Kenpro and Yaesu elevation rotors get zapped
by mother nature.  It has a very distinctive sound like a hammer hitting my
pipe very forcefully.  It is a bad sound to hear in the middle of the night
during a storm because it only means taking all the antennas down to tear 
the rotor apart to fix it and those linear potentiometers are not cheap.

I have had a few 75452 chips get zapped by acts from mother nature.  
This was solved by getting my grounds referenced at the same


Tim - N8DEU
Huntsville, Alabama

----- Original Message -----
From: "Bob Nave" <patcher@skyenet.net>
To: <amsat-bb@AMSAT.Org>
Sent: Sunday, July 08, 2001 11:06 AM
Subject: [amsat-bb] Kansas City Tracker Interface

> Need Help with a Kansas City Tracker Interface Board LLG02.
> The Up Control Output is always at ground level now. Is this a bad
> IC and can it be replaced? If so, where is the IC available from?
> Thanks for reading.
> Bob - WB9CNS
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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