[sdiy] juno 106 repair

[Byron G. Jacquot]

>Here's my situation. I have a Juno 106 with the common bad oscillator 
>problem. To fix that I know I need to buy a new oscillator and replace
>the defective one.
>
>The problem I'm asking your help with, is that the square wave doesn't 
>work. that is, when the sub osc and triangle are turned off it will make 
>no sound. Is there any way I can fix this? Is it related to the previous
>problem? I have an oscilloscope if there's something I can do..

Just a second, let's make sure we're on the same page here.

I assume you put the Juno into the diagnoistics mode, and then cycle through
the voices as you play.  Is there a voice that's entirely absent as you
cycle through?  Or is it just that one voice doesn't make a square wave, but
the sawtooth and suboctave are there?

If that's the case, the voice chip is still good, and whatever downstream
devices mix the waveforms together are having problems.  I don't have the
schematics in front of me, but I seem to recall an analog multiplexer in
there for selecting the square and saw waves...that's probably easier to
replace than the voice chip.

If I've misunderstood your question, please try again, and we'll give it
another go.

Byron Jacquot