[sdiy] Yamaha CS01 - No Noise output (Noise Zener?)

[Bob Weigel]

IS1715P is the number on the diode.  I don't have specs handy but it is 
probably just a zener diode of 3-6V value.  More likely the capacitors 
that are 1uF/50V have either gone dead....or one of the transistors has 
failed.  Failure likelihood on a zener biased with 9v through 120K is 
almost zip I'd think.

-Bob

Chris Manders wrote:

>Hi folks
>
>I am repairing and restoring a little Plasticky CS01
>today. The synth has a problem that there is no noise
>output.
>
>The small noise circuit in this synth is a Noise Zener
>diode, and two amplifying transistors.
>There is no 'noise' at the output or any other point
>in the circuit, so this is the problem. 
>
>Anyone any ideas? Do 'noise' diodes die eventually?
>This synth is almost 25 years old (1982 model).
>
>If it is the Zener, could I replace it with any Zener
>diode or perhaps an old transistor? I don't think I
>would be able to get a 'noise' Zener, if this is the
>problem.
>
>Thanks
>Christian
>
>
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