clh333
Veteran Member
In 1982 I purchased a Kaypro II from a local typewriter shop that was expanding into computers and printers. I made the purchase for the purpose of expediting billing for my fledgling business, and used it for a few years before selling it and moving on to MS-DOS based systems. I would have loved to experiment with the machine - I subscribed to Micro Cornucopia and bought software and hardware accessories - but could not afford the time and did not have the expertise to carry out any modifications. The computer was a tool, and when a better one became available I obtained that as a replacement.
I did however teach myself to program on the K-II machine, out of dissatisfaction with the software available at the time, and ultimately that led to a career in database IT. When I sold the Kaypro I retained the disks, manuals and peripherals, which have been in storage for decades. Lately with equal parts guilt and curiosity I dug them out to see what remained of them. The manuals are fine, the Silver-Reed daisy-wheels are still operable, the disks however are unreadable with anything I have now at hand (TEAC 55 FGR on an XP machine with a late-90s Award BIOS).
So I went looking on eBay for a Kaypro, and obtained a Kaypro 4. That is the reason for this post: The machine has a problem that appears to be common with old Kaypros, but difficult to diagnose. It powers on but does not boot; the LED lights but the screen is filled with garbage characters, some of which vary over time and some of which are fixed.
I looked on line and found a Kaypro TSM, and in the problem / fix section for this machine (full-height Tandons and only one serial port, no modem) three options were presented: Reset switch grounded to case, reset switch harness grounding or damaged, or motherboard needs replacing. Hoping for a reset switch I took the cover off.
The machine had at some time been modified with an Advent Turbo Board, a daughter board that replaced the CPU with extra circuitry allowing switch-selectable. A Z80B processor was on the board, which unfortunately was not in the CPU socket. The pins of the Advent board had been bent and in some cases broken off.
After removing the Advent board, switch and jumper I pried out the Z80B and socketed it in the motherboard. Same result. I removed the reset switch from the chassis; same result. I disconnected the harness from the mobo; same result. I checked the power supply, verifying the 5 and 12-volt pins, which were good. I had a spare Z80B CPU in a bug-box, and replaced the CPU with that; same result. Back to the Internet.
I found a post by someone who had solved this problem, tracing it to a bad socket for a memory chip. I looked at the sockets and all seemed fine. The machine was very dusty but did not seem corroded. Now what?
I have these options: I can replace each chip on the board one by one until something works (assuming I can find them; some gated arrays were custom to Kaypro, it seems); I can try to find a replacement board (probably means buying another Kaypro); I can try to find a technician who can work on this one (not hopeful for that outcome); or I can post a plea for assistance on vintage-computer.com. I figured I would try this first.
Before posting I read the other threads on the CP/M forum; I did not find the solution but forgive me if I overlooked something. I would be very grateful for any suggestions for solving this problem.
Thanks
Charles Hudson
clh333
I did however teach myself to program on the K-II machine, out of dissatisfaction with the software available at the time, and ultimately that led to a career in database IT. When I sold the Kaypro I retained the disks, manuals and peripherals, which have been in storage for decades. Lately with equal parts guilt and curiosity I dug them out to see what remained of them. The manuals are fine, the Silver-Reed daisy-wheels are still operable, the disks however are unreadable with anything I have now at hand (TEAC 55 FGR on an XP machine with a late-90s Award BIOS).
So I went looking on eBay for a Kaypro, and obtained a Kaypro 4. That is the reason for this post: The machine has a problem that appears to be common with old Kaypros, but difficult to diagnose. It powers on but does not boot; the LED lights but the screen is filled with garbage characters, some of which vary over time and some of which are fixed.
I looked on line and found a Kaypro TSM, and in the problem / fix section for this machine (full-height Tandons and only one serial port, no modem) three options were presented: Reset switch grounded to case, reset switch harness grounding or damaged, or motherboard needs replacing. Hoping for a reset switch I took the cover off.
The machine had at some time been modified with an Advent Turbo Board, a daughter board that replaced the CPU with extra circuitry allowing switch-selectable. A Z80B processor was on the board, which unfortunately was not in the CPU socket. The pins of the Advent board had been bent and in some cases broken off.
After removing the Advent board, switch and jumper I pried out the Z80B and socketed it in the motherboard. Same result. I removed the reset switch from the chassis; same result. I disconnected the harness from the mobo; same result. I checked the power supply, verifying the 5 and 12-volt pins, which were good. I had a spare Z80B CPU in a bug-box, and replaced the CPU with that; same result. Back to the Internet.
I found a post by someone who had solved this problem, tracing it to a bad socket for a memory chip. I looked at the sockets and all seemed fine. The machine was very dusty but did not seem corroded. Now what?
I have these options: I can replace each chip on the board one by one until something works (assuming I can find them; some gated arrays were custom to Kaypro, it seems); I can try to find a replacement board (probably means buying another Kaypro); I can try to find a technician who can work on this one (not hopeful for that outcome); or I can post a plea for assistance on vintage-computer.com. I figured I would try this first.
Before posting I read the other threads on the CP/M forum; I did not find the solution but forgive me if I overlooked something. I would be very grateful for any suggestions for solving this problem.
Thanks
Charles Hudson
clh333
