NOTICE: The information presented below was originally published by Walter, KD6YVY at   In an effort to supply complete information for the 'Mint Idea' APRS Tracker project,  I have taken the liberty to reproduce some of Walter's information on the Rand McNally GPS modifications here. While the information presented here aided me in modifying the GPS for use in the 'Mint Idea' APRS Tracker project, readers are advised that I assume no responsibility for the accuracy or suitability of the information presented. Use it at your own risk!

Jim, N2IXD


HACKING INFO:  ===================================================

1. Remove the four screws that hold the GPS together. Pull the two sides of
the plastic housing apart. You will find the hook that is meant to hold the
Palm in place will hinder these efforts. Unhook it as you pull the two sides

2. The GPS circuit board is held on to the sub circuit board by a 5 pin
header. Since I did not have a big fat solder iron tip, I held my solder iron
across all five pins, and slowly worked the boards apart slightly. When there
is enough room, bend the circuit boards back and fourth until all five pins
break. Be careful not to over stress the circuit board. If you have a better
solder iron, or patience with soaking up all the solder you can easily improve
this method. I then removed each individual pin that was left broken in each

3. There is a large diode and a yellow capacitor to move from the sub circuit
board to the GPS board. The items are shown in their final position. To better
see where the capacitor is actually connected to see below.

4. Wire power and a serial cable to the GPS board. Remember to ground your
serial cable!

Here is the pin-out shown in reference to the above picture:

o     Ground
O    Ground
O    Capacitor (polarity doesn't matter) - Replaces bare jumper wire
O    (Square Pad) + Positive voltage 4 to 16 volts DC
O    ? Unknown - but not needed for serial com
O    Serial Output
O    ? Unknown - but not needed for serial com
O    Serial Input

And Walla, you end up with the finished product. A 2" by 3" GPS which should
look like this:

If you can't figure out something neat to do with your lithium battery, send
it to me and I will put it to good use!

Shield the GPS properly and you should have a lot of fun with this GPS.