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Interesting new acquisitions

nblsavage

Experienced Member
Joined
Aug 8, 2008
Messages
101
Location
Beaverton, Oregon
It's been a while since I've posted on here, but things have been quiet. A new acquaintance of my wife and I is moving out of their old house into an apartment and has had to part with some interesting vintage items. I took them because I would be heartbroken to see them go to a dump.

1st thing - an IMSAI 8080 - missing it's CPU card...and in a state of disrepair but still worth saving.
2nd - a Northstar Horizon, which I haven't tested yet.
Along with both of these, I've got a sizable stack of various S-100 cards, disk controllers, memory, I/O, Z80, etc. plus a couple of binders of CP/M and application documentation, oh and a couple of S-100 backplanes including a Wunderbus
3rd - a Zenith Z-100 minus the monitor
4th - a TI 99/4a expansion box with the serial, 32K ram and floppy controller carts.

Now I've got to find a place to put all these and start figuring out how to restore the S-100 systems...I have zero experience with them.
 
Wow.. great find! I haven't really worked with many myself but the biggest thing to check first is the capacitors. Once you get past the power there are some manuals online I'm sure that will have better details on how card configurations work to build yourself a working system.
 
s100computers.com has a really good guide for getting S-100 based systems up and running when you don't know if any components are good. I was pointed in that direction by other forum members when I started repairing my Cromemco Z-2D.

If you have the experience with discrete electronics, I'd highly recommend getting one of the N8VEM S-100 proto boards and building a ROM card with some form of output device (LEDs, character/hex display, etc). I built a similar card, and you can find some documentation on it by searching the S-100 forum topic concerning the Z-2D. I started with hardwiring an 8-position DIP switch to the data IN bus and setting the switch for HALT (0x76)...with a transistor driver and LED wired to the HALT line of the S-100 bus, I could observe the processor HALTing when the instruction was toggled in. Of course, if you've got the IMSAI chassis working well enough to use its front panel, you can skip adding your own output device.

Along the lines of capacitor problems, I found it helpful to get a smaller S-100 backplane running with my bench supply before jumping into the Cromemco chassis. The current limiter on my supply (a Lambda triple-voltage) saved me from exploding some faulty tantalum capacitors, and having the backplane out on the desktop is handy for measuring points on the frontmost and rearmost cards in the backplane.
 
I treated myself to a small backplane which I hooked to a current limited (polyfused) power supply, after unfortunately taking one of the fingers off an S100 pcb when one of the on-board caps was shorted. Everything now gets metered for shorts then plugged in there first.
I wish I'd known how prevalent the shorted tantalum cap thing was, and how under-rated the power supply connections on S100 are, sooner!
 
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