Kaypro Motherboard Add-On Question

Jim Brain brain at jbrain.com
Fri Jan 8 22:25:39 CST 2016

On 12/12/2015 10:52 AM, Glen Slick wrote:
> On Sat, Dec 12, 2015 at 8:32 AM, Jim Brain <brain at jbrain.com> wrote:
>> http://www.ebay.com/itm/USED-KAYPRO-4-COMPUTER-MOTHERBOARD-/331730690952?
>> The non soldermask boad on top of the main unit intrigues me.  Does anyone
>> know what it is?
>> Jim
> The board says Centram Systems, Inc, Camp Hill, Pa.
> There is a marketing blurb in the August 15, 1983 issue of
> Computerworld. Don't know if it is for that exact board.
> Long ugly link:
> https://books.google.com/books?id=soGti0kvtgwC&pg=RA1-PA71&lpg=RA1-PA71&dq=centram-systems+inc+kaypro&source=bl&ots=6Vnr0qZn3W&sig=otazIdpkt4Y5Oyrp9jjKKrv_dq4&hl=en&sa=X&ved=0ahUKEwjHtaP34tbJAhUL9mMKHWnaDYQQ6AEIIDAB#v=onepage&q=centram-systems%20inc%20kaypro
Sorry for the delayed update, but after a few relistings, I was able to 
secure the PCB for a reasonable price.

It is indeed the board listed on the link, and here is another link:


The product is called "KayNet", a baseband twisted pair CSMA/CD local 
network operating at 125kbps.  It uses a network called Web, designed by 
Centram Systems, Inc. of Camp Hill, PA.  The network software , OPSnet, 
was written by Aquinas, INc., and is compatible with CP/M 2.2

I secured the board, but it needs to be reverse engineered and I lack 
the time at present.  Anyone want to take on the effort?

I also need to track down OPSnet OS, and I think there is a bit more to 
this board (the documentation I found mentions a switch and an RJ-11 
connector.  I see what looks like the LED wires on the PCB, and there 
are 3 more pins on the PCB that could be the RJ11 pins. There is a wire 
that is soldered to U65:pin4 on the motherboard, which I assume is the 
switch but maybe hooked to this gate as a way to make the switch a 

Here is some documentation:


Here is the KayNET documentation:

(Thanks Jason Scott!)

Anyone interested in bringing this network back to life?  I am happy to 
design and manufacture replacement PCBs at cost for this...

More on KayNET:


This looks very interesting, but I think I need help to move forward.


Jim Brain
brain at jbrain.com

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