Hi,
I scored a vintage 1988 Casio SK-1 Sampling Keyboard but it was dead. I found at first it had the electronic power switch with an open B-E junction. This was replaced and the keyboard now powers up but there are no obvious indications it is operating. Sometimes when power was turned off it stayed on and vice-versa. It seemed brain damaged. I all the lytics esr tested fine...
When cycling the power switch and turning up the volume to max one could sometimes hear like a whole background of musical notes in the noise. Turning the tuning adjustment affects the overall pitch so I suspect the CPU is doing some work correctly. Sometimes a couple of buttons have an effect on the background notes but not consistently.
I then discovered that jumping some stray signal with a fingertip from some CPU pins to the internal speaker amp that I can hear various octaves of the same note. It would seem that the cpu is playing 1 note. Placing a finger across the LC elements of the cpu clock affects the pitch too so I know the cpu clock is working.
I am guessing that the previous user plugged in a wrong polarity dc adaptor which blew the power switch transistor and partially corrupted the keyboard's program eprom. If this is right then it might be fixed simply by refreshing the program. Does anyone know of a likely source for the eprom hex code of a Casio SK-1 Sampling Keyboard?
A*s*i*m*o*v