Mystery Northstar Advantage Expansion Board

[bigbooster126]

I was going through my Northstar Advantage and came across this custom-made expansion board populating one of the slots. Can anyone identify what the purpose of this board initially was or what it might be able to do?

 

[VERAULT]

Hi and welcome to the forum. You may want to update your avatar to shiw where in the world you are located.

 

[daver2]

Welcome (even though you joined VCFED in 2013). You are still under moderation of course...

I am guessing some sort of interface card between the computer and the outside world. Maybe additional serial or parallel ports, or raw TTL I/O ports? Although for serial interfaces I would expect a 40 pin UART to be present - so strike that idea!

The green card is only used for the gold edge connector to interface the proprietary logic to the backplane - so it tells us nothing.

The card itself only contain basic TTL packages (latches, buffers, simple logic gates etc.) so it could do (literally) anything...

I wonder if there is an IC missing - as there is an empty IC socket.

If it was me, I would do a bit of 'wire tracing' from the edge connector (we know what the pinout of this actually is) and see if we can work out the address decoding. A bit of 'reverse wire tracing' from the external connectors next - to see which pins are wired to IC device inputs and outputs.

Dave

 

[seaken]

Hi @bigbooster126 , welcome to the forum.

I do not know the answer. But I will posit a WAG. I owned NorthStar computers back in the early 80's and there was large group of users in Western NY who used these machines for networking accounting offices. They often had Horizons and Advantages in the same network. NorthStar had their own networking cards but it was not unheard of for some small shops to cobble together their own boards. Maybe this is some kind of network communcations interface that was meant to connect to some non-standard non-NS piece of equipment. Or maybe it was a DIY project by a user to connect to some printer or plotter.

Seaken

 

[abzman]

It's a clone if the PIO parallel card, the chips are even in exactly the same locations. The missing chip is a 74LS03. They used DB25 connectors instead of DA15 connectors though. I just made a replica PIO card and it checks out. https://abzman2k.wordpress.com/2023/03/20/northstar-advantage-replica-pcbs-pio-sio-previews/

 

[Dwight Elvey]

I suspect it was used for something like connecting a paper tape reader or maybe a punch.
Dwight