Yamaha CS80

Thanks for all the detailed suggestions! I'll be getting back down to
the studio today to perform some further investigations, I'll keep you
updated!

-Stephen

On Tue, Jun 17, 2008 at 5:51 AM, Kyle Jarger <jkjelec@...> wrote:
> 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#
>
> 



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