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Mini OSI-300?

Posted: Wed Apr 24, 2019 9:45 am
by CommodoreZ
A few years ago, I purchased a pair of Mr. Bachman's mini OSI-300 replicas. One of them I stashed away for future modification, but the first one I built out and have spent a reasonable amount of time playing with.

Image

During DEFCON last year, I was preparing to use it as a makeshift blinkenlights badge, with a 4017's clock line following the flipflop output. During the course of my messing around, I noticed I could no longer load values into memory. I figured "oh, I've fried some logic chip", and replaced the 7 ICs on the board. No change. I found a diode that tested bad, but again, no change in operation following its replacement.

Recently, upon picking up the board again, I noticed that while LOAD doesn't let me write any values into RAM, if I manually pull down the R/W line on the 6264, it will accept deposited values. Curious. I threw a voltmeter at the R/W line during a LOAD, and the voltage stays high.

If I set the address to a location that has a few stray bits in it, and try to load a value of my own, I notice that that the data LEDs dip low for every switch I have set to 0, and stay on for every switch set to 1 but only while the LOAD switch is pushed. They do not persist after the LOAD is finished.

I imagine at least a few folks here have these mini's in their collections. I'm not sure this problem is applicable to original 300's or just mini's. Obviously something has failed on mine, I'm just not sure where precisely. Any ideas what's going on here?
Alright, ignore all that. I found the problem 5 minutes after posting. Apparently I had another failed diode causing all the fuss.


Therefore, let me shift gears. How many of y'all have a mini OSI-300? Anyone make any fun modifications, or try anything interesting with theirs?

Re: Mini OSI-300?

Posted: Sat May 11, 2019 11:50 pm
by glitch
I've got one, built another and gave to a friend, and still have one unbuilt board, I think. Haven't done much with mine, I need to change out the LEDs as they're stupid bright. It's fun to poke short programs in and let them run, though!

Re: Mini OSI-300?

Posted: Mon Jun 17, 2019 4:42 am
by waltermixxx
Josh has his built, and I am in the process of finishing mine up.
It's a nice little board. I'm going with 4 green and 4 red for the data bus,
going with yellow, green, red for the 3 sets of 4 address leds. :) Pictures to come.

So we will be adding to the small community of owners. :)
Definitely bringing my Mini OSI-300 to VCF MW along with my 600 REV D
displaying colour. :) Cheers. :)

Re: Mini OSI-300?

Posted: Mon Jun 17, 2019 3:29 pm
by gekaufman
Cute board, are any still available?

Re: Mini OSI-300?

Posted: Mon Jun 17, 2019 5:02 pm
by waltermixxx
I'm not sure where Josh got them, i can ask him if he can provide the suppliers name,
but here might be a clue: http://randomvariations.com/ I think he supplied the boards,
not sure if he still has any....

:)
OSI-300mini.jpg
OSI-300mini.jpg (469.37 KiB) Viewed 8617 times

Re: Mini OSI-300?

Posted: Wed Jun 19, 2019 2:52 pm
by glitch
Yeah, they came from Chris at randomvariations -- I think it was a pretty limited run for him, he did supply them with switches on request. I'd message him and find out if he wants to run more, or will at least send you the Gerbers for it.

Re: Mini OSI-300?

Posted: Thu Jun 20, 2019 9:20 pm
by CommodoreZ
I'll have my mini at VCFMW as well. That mini looks really amazing with different colors for every nibble.

If memory serves, the switches were the hardest part to source on that build.

Re: Mini OSI-300?

Posted: Fri Jun 21, 2019 5:47 pm
by waltermixxx
I will bring mine as well (now completed and working.... not without some issues)

It didn't like the initial 6502 I used and would not play nice with it, but I found one it did like.
also my address line A11 switch is wonky might need to replace it. But yeah it's working and kinda neat. :)

I'm going to design a 3D printed case for it, that it would slide into. it will be angled, with a flat bottom, and rubber feat. :) i will post the STL once it's done. :)

Re: Mini OSI-300?

Posted: Sat Jun 22, 2019 11:16 am
by waltermixxx
Here is version two of the enclosure.
I have a version three coming which is a tad longer, and includes OSI 300 MINI embossed on the front. Pictures to come, in the mean time:

for some reason they wont post...
Here is he Flickr link: https://www.flickr.com/photos/66577016@ ... 9200532583

more photo's added with the Final Version with OSI 300 MINI on the front. :)

Cheers.

Re: Mini OSI-300?

Posted: Sat Jun 22, 2019 12:58 pm
by pbirkel
Very nice! But prefer blue :-}. I take it that a longer front-edge will provide better wrist angle/support?