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Kaypro 2

TODO: Overview photo

Computers in Collection

Kaypro 2, serial 140083


Acquired from cupajoe123@eBay in October of 2017. Picked up in Bend, Oregon in December of 2017, if I recall correctly. Very filthy, inside and out.

Blue and gray case. Two half-height 5.25” drives mounted horizontally, one is missing the door handle. There is a modem jack, but it’s unlabeled, and the related parts on the logic board are unpopulated (though many of the ICs have empty sockets). ICs have date codes in mid/late-1983 or early 1984. “81-292” ROM is copyright 1984. Logic board silkscreen says “13/84”, whereas other online photos I’ve found say “22/84”.


Manufacturer Kaypro
Model 81-014
Serial 140083
Color blue and gray
Floppy drives half-height, horizontally-mounted

Logic Board

Manufacturer Kaypro
Part “ASSY 81-__” “MADE IN U.S.A.”
Serial 30511 (hand-etched on PCB)
BIOS ROM U34: “81-292” “(C) 1984 KAYPRO”
Character ROM U9: “GI TAIWAN” KPRO 81235” “9433DS-0023” “8344 CDM”

Internal Floppy Drives

TODO: Determine if drives are single- or double-sided, which would clear up if this is a “2” or “2X”.

Maintenance Log

System would not produce video output when powered on. It was also absolutely filthy, as if dirty water had been dripping down on and in to it at some point.

Kaypro 2 logic board is very dirty

Kaypro 2 logic board is very dirty

Removed all ICs, applied De-Oxit. A couple of the pins on the Z80 chip broke off, due to the pins being terribly corroded.

Tore down the system and cleaned all parts as best I could.

I broke a pin off the fuse holder and ordered a replacement on Mouser (Littelfuse 03450601H). The fuse is 2A 250V “312”, for future reference.


Used XGecu TL866-II to test all logic ICs on the board. Identified one bad gate in U58 74LS373 and two bad gates in U20 74LS245. Replaced, but didn’t see any immediate improvement in behavior. No video output was produced. However, watching the Z-80 activity, it looks like there’s code running to blink the cursor? Some low volages (3V and change) were observed on the LS04 inverters used to buffer the reset signal. I swapped for another, and the voltage levels look better, around 5V. I’m sure there’s more… I also observed some mechanical variability around the pins on the video ASIC and 6545. Maybe replacing those sockets would be a good idea.


Replaced a bunch of ICs, and populated a bunch that were shown in some photos of the board. The processor is clearly functioning. But the video hardware is not. The SY6545 gets quite warm, and the 81-189 custom IC doesn’t seem to be producing signals. I was wondering about the “E” signal going into the SY6545, and was expecting to see some activity on it, but don’t. Because the custom IC seems the most likely suspect, and I have no means to test it, I’m kinda stuck for now…

TODO: Was this the system whose CRT I removed the Aquadag? That needs to be remedied somehow, assuming one can still purchase Aquadag, and it’s not impossible to work with safely…

TODO: I got a new Kaypro with the OMSI donation, and it might have some common chips that would be useful for diagnostic swapping with this system.