[vcf-midatlantic] Ohio Scientific 495 Prototype Boards

Systems Glitch systems.glitch at gmail.com
Thu Feb 11 11:27:44 EST 2016

I finally found an Ohio Scientific 495 prototype board recently, on eBay! I've been searching for one for years -- I only know for sure of one other 495 board in existence. Apparently they're desirable, as I had to pay > $100 for it. Here's what I got:


The previous owner didn't get much done with it -- looks like they had laid out some buffering and that was about it. I stripped it off, which was super simple as the board is single-sided with no plated-through holes. I was going to start using it when I thought, wouldn't it be cool to reproduce the boards so other people could get them? I removed the Molex KK-156 connectors in preparation for scanning the board and making UV photoresist negatives. Instead of making a photocopy board, though, I sent it off for a high-resolution scan and conversion to DXF/Gerber+Excellon Drill files. I got the results back yesterday:


It's a 1:1 scan with no clean-up, so the scan definitely reflects the "tape and film" original. Not all of the pads are perfectly lined up and the drills aren't always on center. I decided to leave it like that as it doesn't really harm such a simple board. I did add a bit of text at the bottom left corner, so that the reproduction boards don't end up misrepresented as brand-new originals or something.

I sent the Gerbers off to get a small test run done, but I'll probably do a much larger run (25 or more) once they're proved out. If anyone wants one, let me know. I'm going to put together some tutorials/plans on how to use them to build useful OSI-compatible boards -- like a RAM board that uses 32K x 8 "modern" 28-pin static RAM! 


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