New tools and more memoryI don't have many cards installed in the IMSAI chassis, so I've usually had plenty of room to troubleshoot them. But there have been evenings in the retrolab spent in awkward, arm-twisting contortions trying to get my increasingly shaky scope probe down in the chassis while looking up and still trying to be vigilant not to short out any pins or lean over into the power supply area. So, I built the N8VEM Extender board. And you know, what better way is there to get that vintage computing experience than assembling a mail-order kit? I love the smell of burning solder rosin in the morning. It smells like... victory.  The first board I worked on was a Solid State Music 8K SRAM.  Wow, that unmasked blue PCB is pretty. Chip U47 is missing on this board, but the manual (p.7) explains that this is to deactivate memory protect for front panel computers without that feature. After straightening out the addressing, I found that the board actually (mostly) works. There are a few dead bits on a couple pages that I need to sort out, but it seems to be in much better shape than the IMS board. This board was relatively easy to get up and running at first, but then had me scratching my head. The fundamentals were sound—no shorts on the caps, the 7805s were within tolerance. Once I figured out the switch settings, I set it for 2000-3FFF—a second 8K. That seemed to work. Most of the memory seemed fine, but then I started running into problems here and there. Playing around with a monitor program, I was having trouble writing to some locations. But the front panel could deposit and examine fine. Anyway, after going around in circles a while, swapping out a few 2102's resolved the issues. 16K. Imagine the possibilities. Page listing - "Subpage Listing" |
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