Yamaha CS80

Something with the discrete DACs may be wrong. There are resistor ladders 
which are handled by switches inside the ICs - maybe one of the resistor's 
solder joints is bad? That might cause a systematic error such as you 
described, as the DAC is not binary, but organized in Octaves and Semitones.

(Just an idea - can't dig deeper into this right now.)

JH.

----- Original Message ----- 
From: "skkatter" <skkatter@...>
To: <yamahacs80@yahoogroups.com>
Sent: Monday, June 16, 2008 11:15 PM
Subject: Re: [yamahacs80] Re: CS60 playing wrong notes problem


I've had a look at the KAS, all the solder points have the correct
colour wires as per the circuit diagram (and as one would expect!).

-S

On Mon, Jun 16, 2008 at 10:31 PM, erikfromhere <moogsynthex@...> 
wrote:
> Strange problem. My guess: either the keycoder is putting out wrong
> data or the dac is having problems with it note-ladder-network. Maybe
> some faulty resistors in the network ?
>
> I can't imagine someone having soldered wrong the wires coming from
> the keyboard to the kas-board. But it can't be wrong checking:
> solderpoint 25 on the KAS, D# input, must be a yellow wire for
> instance.
>
> Good luck !
>
> --- In yamahacs80@yahoogroups.com, David Rogoff <david@...> wrote:
>>
>> skkatter wrote:
>> > Hello! I'm one of the new members mentioned a while ago. :)
>> >
>> > I just bought a Yamaha CS60, which according to the seller was in
>> > great working condition, but upon arrival it is exhibiting a
> problem.
>> > Perhaps somebody has come across this before or could guide me on
> what
>> > to check?
>> >
>> > Basically some of the keys are playing incorrect notes. On each
>> > 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#
>> >
>> Ok, this is strange. First, look at the KAS chip spec
>> (http://www.therogoffs.com/cs80/manuals/CS60_Service_Manual/06%20-%
> 20KAS%20ICs.jpg).
>>
>> Note N4N3N2N1 Note heard
>> C 0001 Good
>> C# 1111 Good
>> D 1110 Good
>> D# 1101 1111 - N2 stuck @ 1
>> E 1011 1111 - N3 stuck @ 1
>> F 1010 1110 - N3 stuck @ 1
>> F# 1001 Good
>> G 0111 Good
>> G# 0110 Good
>> A 0101 0111 - N2 stuck @ 1
>> A# 0011 0111 - N3 stuck @ 1
>> B 0010 0110 - N3 stuck @ 1
>>
>> I don't see anything obvious. Anyone else?
>> Have an Oscilloscope? A spare KAS chip :^)
>>
>> David
>> > All the notes are perfectly "in tune", but exactly half of them
> are
>> > playing the wrong note. This happens for all octaves, each wrong
> note
>> > is in the same octave as the other notes (ie when I press f3 I
> hear a
>> > d3, when I press f4 I hear a d4).
>> >
>> > The seller assured me it was working fine when it left him, and he
>> > tuned it before it left. It travelled via a courier company from
> Paris
>> > to Berlin so perhaps something has moved around a bit inside (the
>> > seller seems genuine so I believe that it left his place in
> working
>> > order).
>> >
>> > This is my first Yamaha CS synth so don't know much about them
> (for
>> > example, how do you open up the front panel? :)) I do own a
> multimeter
>> > and would be willing to measure voltages to find the source of the
>> > problem. Has anybody come across a fault like this before, or
> knows
>> > what I could check?
>> >
>> > One other thing which may be worth nothing, according to the
> seller, a
>> > French technician called Jean-Loup Dierstein has installed a
> simple
>> > little kit inside the CS60 which tells you via 8 leds which voice
> you
>> > are playing when you press a key. (this might come in handy!) I
> can
>> > hold 8 keys down (ones which play different sounding notes
> anyway) and
>> > hear 8 notes at the same time .
>> >
>> > So, what to check next? (thanks in advance)
>> >
>> > -Stephen
>> >
>>
>
>



-- 
http://www.skkatter.net

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