Before I got my 400 board, I had narrowly missed out on this auction, which is only available via worthpoint now. I had originally thought it was an OSI produced 400 board, but looking closer now I'm not so sure. The first thing that caught my eye was the lack of tinning. That didn't flag anything for me when the auction was active because my OSI 300 isn't tinned. But I see looking at the board again it uses wirewrap sockets, which was practice for when you didn't have through plate vias. It looks like that's how they're being used here.
So I'm wondering, did someone just rip this off somewhere? I'm wondering where they got the artwork from back then. Or is it just a really early one?
https://www.worthpoint.com/worthopedia/ ... 3930447017
Was this a real OSI 400?
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dave
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Re: Was this a real OSI 400?
This is a strange board. I lean towards believing this was made by OSI. The traces, even the oddball ones, seem to match the original artwork. The artwork was published in the manual, but back then, replicating the artwork so perfectly would have been very difficult, and replicating the fonts so precisely in multiple sizes would have been remarkable, especially since back then, there was no incentive to be so precise.
On the other hand, there is no tinning, as you point out. I also suspect the holes may not be plated-through, as there are quite a few wires soldered through vias, and several sockets are raised, which would allow soldering both sides of the PCB. Could this be a prototype?
The chips, sockets, and caps all seem period correct.
On the other hand, there is no tinning, as you point out. I also suspect the holes may not be plated-through, as there are quite a few wires soldered through vias, and several sockets are raised, which would allow soldering both sides of the PCB. Could this be a prototype?
The chips, sockets, and caps all seem period correct.
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Mark
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Re: Was this a real OSI 400?
While skimming through some old links I had saved, I rediscovered the OSI 400 photos at Vintage Computer.Net. Included in the photos was a board labeled "4KRAM Bad" which seems to be an early OSI 420 board, also without tinning, labeled as a board with "bad etching". Perhaps Falter's board was found flawed somehow and left in a state similar to this board? This 4KRAM board differs from the 420C I have seen, but is very similar. It only has 8bit memory layout instead of 12bit, missing a socket or two, plus no holes yet? The layout & traces seem the same as the 420C though for the most part. Maybe its just a variant I haven't seen.
- vintagecomputer.net 4KRAM_bad.jpg
- 4KRAM_bad.jpg (418.37 KiB) Viewed 1388 times