Vintage Synth Repair

Hi,

does this really happen randomly, or something like every time you played
something like 6 or 8 notes (whatever the notes...) ?

A demultiplexer (surelly a CD4051, or something similar) could be faulty, the
only thing one wouldn't understand is why would it happen only with square
waves... ! If it really does, and your demux / s&h circuits are fine, then I
think it could also come from the adress/data bus, as the DCO and dacs used to
generate the enveloppes should share the same bus.

Look at the MKS-70 schematics, as it seems to basically be two JX-8P in a rack.

Michel

> Hi group.
> I'm searching for a pdf file of the service manual for the roland JX-8p.
> My JX-8p has the following problem:
> - When I select a program which uses a square wave and an envelope with
> fast attack (piano like) some of the notes sound weaker than others,
> but in an alleatory way from patch to patch.
> This also happens when notes are played from an external keyboard thru
> MIDI IN.
>
> Any suggestions?
>
> Best regards and merry christmas to you all!
> Jos\ufffd
> Portugal
>
>