Ok I finally got this to work and thought I would put it down on paper er web page so someone else might be able to use it.

The Rand Mcnally GPS that I have is the PC version. I will give them a minus 50 for documentation or lack there of which is more like it. The PC version has 1 cable running from it and then splits into a DB9 connector(female) for a laptop serial connector and a PS2 connector(male) for the mouse connection. Since there was no wiring diagram or anything else to go by I opened it up and found it had 4 wires to the connectors.

Yellow (DB9 pin 3) (data)

White (DB9 pin 2) (data)

Red (PS2 pin 4) (power)

Black (PS2 pin 3) (ground)

A PS2 mouse connector uses 5vdc so I chose to make a 5VDC regulator for that connector. Allot of GPS units take 5 to 28VDC and since there was again no documentation I thought it best to keep it at 5VDC

Parts used:

1 7805 +5VDC Regulator (RS 276-1770a)

2 .022MFD Caps (RS 276-1475)

1 Heat Sink (RS 276-1368)

1 Project box w/PCB (RS…Your choice)

1 Coaxial DC Jack (RS 274-1563a) (12VDC in)

1 PS2 (female) jack (5VDC and Gnd)

I did not want to change the GPS cable so that I could use it on a laptop or my computer and that is the reason for the external voltage regulation.

I used a gender changer and Null Modem cable for the DB9. In theory the Null Modem cable will switch pins 2 and 3 so Txdata an Rxdata are reversed. This was supposed to work so I thought. Well as it turns out, I had to jumper pins 2 & 3 together and run it to pin 2 on my DB25 cable for the TNC to get the data.

DB9 DB25

Pin Pin

2------to------ 2

3------to------ 2

To set up my TNC and that was it.