First post, by babtras
- Rank
- Newbie
I had a dead Kaypro II up until recently. I was able to verify that it was only mostly dead and it only had a dead display but could otherwise be booted.
After swapping ICs endlessly with another, working Kaypro II, and with the guidance of someone on Facebook, it was narrowed to no clock on the video controller portion of the board.
After a lot of head-scratching I finally went through my collection and found a 14.318MHz crystal on a Trident 1MB video card, "borrowed" it at soldering gun point, and swapped out the 13.9776MHz crystal on the Kaypro II.
And with that, the display came to life, mostly.
Now there's this problem:
As you can see, this affects the lower 1/3rd of the screen, exactly 8 of the 24 lines. Some of the corrupt data on the screen is the same every time, and some of it changes.
The system RAM and video RAM are all ok - verified by shuffling them and them swapping with the working Kaypro.
Every IC relating to video was swapped with the working Kaypro also, no changes. All traces have been tested for continuity to verify address lines working, and the issue doesn't seem to be at an obvious address boundary (1280 bytes, not 256,512,1024 etc that would tell me it's at address line 7, for example.
ROMs were also swapped with the working Kaypro, no change, proving the ROMs were not corrupt.
Any ideas?