Hi Constantin.
Welcome to the group. Sounds like it's probably a simple problem. If you look at the giant, overall schematic (
http://therogoffs.com/cs80/manuals/CS80_Service_Manual/cs80_foldout_schematic.jpg ), you'll see in the upper left corner that the keyboard is scanned as a matrix, like a computer keyboard, from the KAS chip. The low octave (not counting the lowest C, which has its own special pin) all have the U1 signal in common from the KAS chip / board. If you look at the KAS circuit board layout (
http://therogoffs.com/cs80/manuals/CS80_Service_Manual/05%20-%20KAS%20Circuit%20Board%20&%20Wiring.jpg ), on the right edge of the board, about a dozen pins from the top, is this signal, U1. According to the invaluable wiring labels, this is a red shielded wire that connects to C1 - the lowest key. You can see the wires on the circuit board at the back of the keys that holds the metal key contacts. You'll see that each circuit board hold 6 keys except C1, which is all by itself. Since that key works and the next octave doesn't, it looks like the jumped wire that connects U1 from that little C1 board over to the board next to it is broken.
If you're somewhat familiar with electronics and know how to open up the lid, this should be pretty easy to check. If not, find someone who is!
Good luck,
David
On Dec 3, 2012, at 9:12 PM, "Constantin" <constantinz@...> wrote:
> Hi there,
>
> My CS80 was working fine until today, when I noticed the lower octave stopped triggering any sound. All other keys, ribbon and knobs work great.
>
> More specifically, the lowest C key on the left of the keyboard works but every key after D, E, F, G, A, B, C (and the respective black keys) does not trigger any sound. The second octave (after C) and all other keys work just fine.
>
> If anyone has experienced something similar and was able to fix it, would love to hear back. Also any advice is greatly appreciated. Thank you for your time,
>
> Constantin
>
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>