I have tested the new CPU replacement board outside with a 12V supply. When finally mounting it to the uProc board and used the 6.4V supply of the board I run into one issue. The clock signal for the CD-CPU should be 5.8MHz but was flat.
One issue have been the two capacitors I was using for the 7805 to power the 5V for the AT1284P CPU. Removing them only gave a short time a clock but flatten at some point. I am not sure if there are some interferences with the CPU. At the end I removed 3917 and the bridge 475 and put a crystal on the back of the PCB with 6MHz as a clock for the MAB8441 CPU. That is doing the job and since both CPUs are not synchronised (6MHz for the CD CPU and 16MHz for the Tape Deck CPU) I am going to solve key events by keeping the lines up or down for some milliseconds. We are not talking about a realtime OS.
Due to changes in the replacement PCB I am going to do some design changes for the second release. However, this board can be used for further testing and improvements.
At the end the uProc is almost finished. It got all brand new quality capacitors, the CD CPU is working and the clock is stable, the CPU replacement of the tape deck is working. The only thing left is a little bit of flickering of the CD LCD display. This might be the LCD Panel itself which I had to remove completely to clean the extremely dirty display.
