Kantronics KPC-3 (non plus)

Quick guide to Upgrade your KPC-3 (non plus) and other obsolete Kantronics TNC’s

Well if you found this by searching the internet you are probably wanting to know how to upgrade your old KPC-3 (non plus) TNC to the latest 8.2 firmware. Well Kantronics no longer supports this great TNC. That is rather irritating to me so I went on a mission to solve this problem. Well fret not……You can buy an inexpensive EPROM chip and a programmer and fix your own TNC. Once upgraded the TNC works great on APRS.
IMPORTANT – Write down all your TNC settings. The following process will erase all your TNC settings such as your call sign, settings, and any mail you have saved in your mailbox. Save it, write it down, do something.

Take the little screws out that hold the top cover on the TNC. Once the cover is off, one of the bigger chips inside the TNC will have a white sticker on it that states the “KPC-3” and the firmware version. This is the chip you will replace so make sure you put the new one in the same way the old one is. You will see a little notch on one end of the chip (see below). Make a mental note on the chips orientation.

Above is a KPC-3 (non plus) with a v5.1 firmware chip.

Above is a KPC-3 (non plus) with a v6.0 firmware chip.

I took my version 5.0 firmware chip out of my TNC and pulled the sticker off. It’s a very common M27C512 EPROM chip. They cost about $5 and you can buy one from many online stores such as:
The chips come in many speeds but my original chip is a 200ns.  You can buy anything faster than 200ns and it should work fine (example 150ns, 120ns, 100ns, etc.)  Avoid the slower chips like 250ns.  They might not work.
You do not have to pull your sticker off just leave it on. I removed mine to identify the chip.

Here are two chips I purchased online. They are the same and you only need one. It is possible to erase your original chip by exposing it under strong UV light however I discourage this. I would keep your old firmware chip in a safe place in case you mess up.
Now you need an EPROM programmer. I bought a cheap Willem EPROM programmer off Ebay for about $30. There are many cheap programmers that will work just make sure it supports the 27C512 series EPROM chips. Do a search on google or ebay to find one.


The programmers come with easy to use software and support USB or the printer parallel port. Mine even came with a cable.
All you have to do it plug the new M27C512 chip into the programmer as per your instruction manual, run the software that came with the programmer, and finally load the 8.2 Firmware file. Press the “Write” button and wait a few minutes while the new firmware chips is being written. Its just like burning a CD on your computer.
When its done, you can reinstall the new firmware chip into the TNC and turn it on. All your original TNC settings will be erased and you will have to reprogram your call sign and settings back into your TNC.
Thats it.
Download the Firmware below:
KPC-3 (non plus)  5.0 Firmware
KPC-3 (non plus) 5.1 Firmware
KPC-3 (non plus) 6.0 Firmware
KPC-3 (non plus)  8.2 Firmware
KPC-3 (non plus) Manual
KPC-3 v8.2 Rom Manual Addendum
Good luck.

Firmware for other Kantronics TNC’s:

KPC-9612 (non plus)  v6.0 Firmware

KPC-9612 (non plus) v7.0 Firmware

KPC-9612 (non plus) v8.2 Firmware

KAM v5.0 Firmware

KAM v6.1 Firmware

KAM+ v8.0 Firmware

KAM+ v8.2 Firmware

KAM+ All Firmware, Schematic,  & Parts List

KPC-2 v5.02 Firmware ,  Schematic,  & Parts List

KPC-4 v5.01 Firmware,  Schematic, & Parts List

Excellent old packet TNC software PaKet v6.2


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