Vintage Synth Repair

This might help: http://www.arpodyssey.com/odynois.gif

This is basically the MkII+ noise circuit, or so I understand.

Not sure how easy zener diodes are to find, though.



--- In vintagesynthrepair@yahoogroups.com, "Johnny" <cockandswan@...>
wrote:
>
> neither are "noise". the "pink" noise is just a slightly different
> tone of the weird waveform i mentioned before. i messed around a
> little bit "circuit bending" it with another transistor pluggined in
> at the same time and got something closer to white noise but still
> with a strange pitch.
> 
> is there a way i can find an older transistor or a better match? i'm
> using a transistor labeled "2n 5172" with an F icon on it, so i'm
> guessing it's a fairchild brand? something like that. i know i am
> replacing a "sel 2n 5172"... maybe these two are too different?
> 
> -johnny
> 
> --- In vintagesynthrepair@yahoogroups.com, "balderson04"
> <djacklin@> wrote:
> >
> > Hi, Johnny:
> > 
> > The service manual's description of the noise circuit mentions that Q9
> > is specially chosen "for optimum avalanche characteristics", so it may
> > be that the transistor you've installed is not breaking up in the same
> > way.
> > 
> > Try listening to the noise output at pin 6 of A3 and comparing it to
> > the output at pin 6 of A4.  The first should be white noise and the
> > second pink noise.
> >
>