Last month, I traveled to Sofia, Bulgaria, for a work trip to visit a subcontractor where a friend and former colleague of mine works. While there, I explored local auction sites and stumbled upon an intriguing domestic computer: the Правец 8C, an Apple II-compatible machine. My search for expansion hardware led me to a classified ad for one of these computers. My friend kindly reached out and arranged a meeting to purchase it. To my surprise, the seller turned out to be Ralle! A creator of expansion cards for Apple II systems.

The computer had an issue with erratic keyboard input, but Ralle provided me with an Apple II USB keyboard adapter as a workaround. A challenge is just an opportunity to learn more about the machine. Additionally, the computer came equipped with both an A2DVI and an A2Pico card. I managed to bring the 9” monitor home in my suitcase, while the computer itself traveled as my carry-on luggage.

The irratic keyboard was solved by removing a automatic F1 keypress mod (if I understood Ralle correctly), running a bodge wire for a poorly repaired damaged trace, and cleaning flux and resoldering the 74145 logic and the CM650 keyboard controller chip. Outputs on the 74145 and two inputs on the CM650 was not a direct short, but had about 15-20 kΩ resistance. Removing old solder, cleaning the pads and pcb thourougly, and resoldering the pads it the resistance is in the megaohm range again. A quick test showed the “3” key to be difficult to register, but a brush of liquiwire conductive paint on the plunger pad solved it.

[{"url":"74145.jpg","alt":"Solder pads of the socket containing the 74145 logic IC. They are very close together.","title":""},{"url":"cm650.jpg","alt":"Solder pads of the socket containing the CM650 controller chip","title":""},{"url":"bodge.jpg","alt":"Bodge wire to fix a bad connection to a missing pad. Missing pad was previously solved with solder dragged to the trace.","title":""},{"url":"debug.jpg","alt":"Troubleshooting the phantom keyboard presses. If you do not have a keyboard plunger, rolling a silver coin over the pad works great","title":""}]

On the wishlist is a serial device and a terminal emulator to be able to connect to our BBS.