Moonferret
Experienced Member
Hi Folks!
I recently took a gamble on a spares & repair Kim-1 that was listed on Ebay. I had read that if the 6530's were dead then it would be a very pretty paperweight but I thought what the hell. I've always wanted a Kim-1 and love the simplicity of early SBCs
Anyway, machine arrived and yup, it was faulty. I decided to check the obvious, reset signal, bus activity, etc. Ahh, no clock signal! Wired up an external 1Mhz clock and it seemed the CPU was pulling that down. CPU replaced and I then had a clock signal but nothing on the display and the CPU stopped running after a second or so. Next step, check memory decoding was working. Nope! Replaced a 74145 and I had some signs of life. Yay! Occasionally, hitting reset would light up some of the segments on the displays. After a bit more troubleshooting (Using piggyback method) I discovered two faulty RAM chips so these were swapped out.
Yes! it's working! ... Almost! The display was coming up with a memory address and contents. I could examine and edit memory but there were a few non-working segments on the displays. I figured I was almost there so ordered a couple of replacement displays. I decided to replace all 6 to ensure even brightness. Again, almost there but not quite. The bottom segment on each of the displays wasn't working. This was traced to a faulty 7438 which was swapped. Woohoo! I now have a working Kim-1
Still got a few bits to tidy up such as cleaning the board and removing the temporary socket the CPU is in but I'm really happy with the results. Here's a photo...
Cheers,
Dave
I recently took a gamble on a spares & repair Kim-1 that was listed on Ebay. I had read that if the 6530's were dead then it would be a very pretty paperweight but I thought what the hell. I've always wanted a Kim-1 and love the simplicity of early SBCs
Anyway, machine arrived and yup, it was faulty. I decided to check the obvious, reset signal, bus activity, etc. Ahh, no clock signal! Wired up an external 1Mhz clock and it seemed the CPU was pulling that down. CPU replaced and I then had a clock signal but nothing on the display and the CPU stopped running after a second or so. Next step, check memory decoding was working. Nope! Replaced a 74145 and I had some signs of life. Yay! Occasionally, hitting reset would light up some of the segments on the displays. After a bit more troubleshooting (Using piggyback method) I discovered two faulty RAM chips so these were swapped out.
Yes! it's working! ... Almost! The display was coming up with a memory address and contents. I could examine and edit memory but there were a few non-working segments on the displays. I figured I was almost there so ordered a couple of replacement displays. I decided to replace all 6 to ensure even brightness. Again, almost there but not quite. The bottom segment on each of the displays wasn't working. This was traced to a faulty 7438 which was swapped. Woohoo! I now have a working Kim-1
Still got a few bits to tidy up such as cleaning the board and removing the temporary socket the CPU is in but I'm really happy with the results. Here's a photo...
Cheers,
Dave