Yamaha CS80

Hi All,

The note assignment table shows the note output in relation to the N1 
through N4 signals.  The table shows N1 through N4, but IC1 on the KAS board 
actually puts out the inverse of these signals, /N1 through /N4.  It looks 
like you will get the "wrong note pattern" you are showing in the case where 
/N2 and /N3 are somehow shorted together, such that if any one of them is 
high, it wins the battle and pulls the other one up as well.  It looks like 
the ouptuts of IC1 each have a 22K pull-down resistor, so it makes sense 
that if two signals were shorted, the high level would win the battle (the 
high output being actively driven by the IC, the low level being only 
passively pulled down by the resistor).  My first guess is that two of the 
22K resistors running along the side of IC1 in a "vertical mount" 
configuration have shorted together, as one resistor has leaned over as 
result of the shipping movement, such that the exposed leads of the resistor 
are shorting out to the lead of the next resistor over.  If this is the 
case, it should be visually apparent when looking at the KAS board.  A 
simple readjustment of the resistor position to get rid of the short should 
fix the problem.

If that disn't work, I'd use an ohmmeter (between pins 26 and 27 of IC1 on 
the KAS board) to see if there is a dead short between /N2 and /N3. If there 
is, maybe you can find a small piece of metal that fell between the pins of 
an IC, or on the PC board, from the movement during shipment. I'd check the 
bottom of the PCB baord as well, for bent pins or an errant piece of metal.

If its not a dead short between the pins, then it is likely one of the ICs 
is bad. In my experience its usually the CMOS support ICs that have failed, 
not the custom yamaha ICs, and so I would replace IC4, a TC4050 chip, first. 
Even though this chip only has /N2 and /N3 as INPUTs, not Outputs,  I recall 
that in some cases a failure in the chips can actually affect signals that 
are only inputs to the chips.  If this doesn't do it, I fear its one of the 
Yamaha custom IC's, IC1 or IC2.

Good Luck!

Kyle Jarger

> octave, when I press c, c#, d, f#, g, g# they all play fine.
>
> However when I play the other notes they do the following:
>
> I press d#, I hear a c#
> I press e, I hear a c#
> press f, I hear a d
> press a, I hear a g
> press a#, I hear a g
> press b I hear a g#