Commodore Magic Voice came in for repair.
The (speech) audio didn’t work or the speech was mangled.
What I did:
- Reseated IC’s, didn’t fixed the problem.
- Measured the clock of the Y1 osc, which should be 640KHz, and it was sometimes 640KHz.. but mostly it was fluctuating.
So I replaced the C1 & C2 ceramic capacitors, the clock is now stable. - Replaced the electrolyte caps.
- Resoldered oscilator and the 2SC2222 transistor.
- Reseated the IC’s again just to be sure they are fitted good.
It works!
Technical resources
http://www.stefan-uhlmann.de/cbm/MVM/Hardware/index.html
http://www.stefan-uhlmann.de/cbm/MVM/Firmware/index.html