Альфа БК (Alpha BK): Part 5 (Reset Button Added) [TCE #0456]
21Not much forward progress today: I added a RESET button successfully (button in parallel with a 1nF capacitor and the !RESIN pin 2 of the 8224) and replaced the two electrolytic capacitors. I also socketed the character EPROM.
Somehow I managed to add chroma to the video signal (very red hue) when I was probing the character EPROM with my oscilloscope - solved by desoldering the ROM and installing a 2716.
Interestingly the boot text prompt has now corrupted further:
АЛьФА-БК ... АДПФА%БЦ ... ЮДПФЮ$БЦ
Anyway, I'm now convinced that the issue isn't with the character ROM outputting the wrong character but maybe with the RAM like several of you suggested already. Yay!
Big thanks to everyone who took the time to leave a comment: @yurasergienko6890, @jpenner6463, @jason-birch, @martindejong3974
From the Part 1 video description:
The Alpha BK is a mass produced version of the famous Радио 86РК (Radio 86RK), an Intel 8080 (clone) based home brew computer detailed in "Radio" magazine (in 1986):
https://en.wikipedia.org/wiki/Radio-86RK
Lots of info here - including a modern version of the original Radio 86RK design:
https://github.com/skiselev/radio-86rk
Information about the Alpha BK:
https://github.com/alemorf/retro_computers/tree/master/Alfa-BK