Update:
I finished the first of two KBC boards. A bunch of pictures are in
Photos -> CS80 Renovation -> KBC. The caps on the back of each IC go
between VDD and VSS. The strange thing is that usually VSS is
0v/ground and VDD is anywhere from +5v to +18 for CMOS. However,
since the CMOS digital chips are also being used to swtich analog
control voltages, Yamaha uses +8.5v for VDD and -6.5v for VSS.
Therefore, the little bypass caps bypass the two supplies to each
other, not to ground. On the TSB board I put seperate caps to ground
from each, but there weren't easily accessible grounds on the KBCs.
It's ok, just not optimal. In the picture
cs80_kbc_after-empty_sockets you can see a couple of big, blue bypass
caps on the front of the board (left edge, top and bottom. These do
bypass the VDD and VSS seperately to ground.
One more KBC to go. Did I mention this stuff is a real pain to do?
The desoldering station is lots of fun, though. I hope to finish all
the CMOS replacement in the next week, or so. I'll be selling the
desoldering station then, so let me know if anyone wants to buy it!
Here's the eBay auction where I bought it last month:
. I just
want what I paid for it.
David
