First post, by Z80Dad
Hi!
I recently bought my childhood computer and am in the process of restoring it.
When I found this wonderful thing on marketplace last week I was debating if I should jump on it or not. I recently bought a Kaypro with no video, and am already up to my ears in restoration madness! But how could I pass it up? This is my childhood computer - same make (very similar model) and I had been searching for one for some time.
First problem -- won't shut off.
Computer boots fine but when shut off it clicks and resets forever until you turn it back on.
Funny right? Well it has a soft power system that for the life of me I can't wrap my head around so I replaced the power supply with a rewired ATX supply I had been saving in a box with the uncommon -5v line for just such an occasion. I went with directly soldering the wires to the supply instead of an adapter because the space is at a premium and if I was going to use an adapter it would add considerably more wires to the mix. I've done this before with success and I was going to have to work some way around the soft power anyway so I just wired pwr_on to the closest ground leg and for now I'll just heat shrink it and turn the power on and off from the switch at the back of the supply (I'm lucky there). This worked like a charm and I'll knock together something with an Arduino to re-enable the soft power at a later date. As for the on board soft power it doesn't seem to do anything if it's not hooked up, and I don't have any way of figuring it out without schematics (which aren't available even when digging really deeply on the Internet)
Firmware update, trying out a flash eeprom:
While not specifically designed for the SST39SF010A checking the voltages at pins 31, 30 and 1 show 5v with the exception pin 30 which is floating -- this seems perfect. A quick check of the datasheet verifies if we hold WE# high at reset blanking and writing is inhibited, again looks perfect. Additionally, the M27C1001 isn't really available from a reliable source any more (you can get them on ebay/they usually work anyway). So I burned a new flash eeprom (Major Toms upgrade to allow DX2 and up on chip caches), socketed it and everything appears to boot up just fine!
Obviously this will take some testing/research to verify if we really have VCC on the write pin or if it's wired somewhere else.
That's about it for now. I'm ordering a picoGUS and upgrading the L2 cache. I'll probably build the 3v interposer and try a 5x86 as time allows. But it's early days yet.