Pac-Comm TNC-220 Manual (Manual also covers other model of the Pac-Comm TNC range)
Allow full duplex at 9600 baud
Hello All @ AMSAT The following modification to the 220 will allow your Tnc to operate at 9600 bauds in Fullduplex. For those of you who thought you already could I suggest you try it. It must be mentioned at this stage that the version of my 220 is 1.3. If yours is a different version then the story may be different, but I doubt it. The reason for this mod is to allow my station to operate on UOSAT3 FULLDUPLEX Previous to this mod I have been ripping my hair out as to why I could not digipeat via UOSAT3. When one day I discovered that when I changed the baud speed to 9600 and then put Fullduplex on the txbaud rate changed back to 1200 whilst the rx rate remained at 9600. Most perculiar I thought. So, I got in communications with the main Agent in the UK for Pac-comm to see if anyone else had this same problem. No came the reply, obviously no one else has tried it yet I thought. So here I am stuck with a TNC that is no use to me for UO3. Can you help me then please I asked Agent. Yes we'll see what we can do. In the meantime Rep has been to Paccomm across the pond and I am told that they work alright over there. Cant be I said! So anyway he suggests I try changing the thirmware which I did but still no good. Ok we'll send them another Fax they said. Fine! Another phone call to Agent 2 weeks later, no info or reply. So I put pen to paper and addressed the same question to the Gentleman concerned at Pac-comm. To date Ive no reply, letter sent some 4 months ago. Not impressed! With UO3 software now on release, and uploading and testing of UO3 bulletin software imminent I figured I had better do something. The result is a crued cure. 9600 FULLDUPLEX on the Pac-Comm TNC-220 by D. Hulatt G4WFQ 19th Aug 90 ------------------------------ Locate 74HC4020 and remove from IC socket CAREFULLY bend pins 1 and 12 up Solder flying leads to pins 1 and 12 on 74HC4020 Solder flying lead to pin 12 on SIO 8530 chip Use a SPDT switch to switch to 2 signals from 4020 to SIO Replace 4020 Drill 1/4 inch hole in rear plate above RS232 slot Insert switch and secure. Thats it. Throw switch for 9600 FULLDUPLEX operation, revert for normal. NB: You still have to change buad rate in s/w. I hope this information will be of use to some. I would like to thank Uk Agent for trying to get info from Pac-Comm. It must be like trying to get blood out of a stone. Thanks Pac-Comm, no need to bother now I've done it myself! 73 de Dave G4WFQ @ GB7PET AUK.2404 19 Aug 90
Updated firmware / EPROM for the Pac-Comm TNC-220
None known to be online. If you do have a copy, please let me know.