Yamaha CS80

rj krohn wrote:
> hi folks, i wanted to ask why a particular mod has never been
discussed, or done, to my knowledge on CS80's. hoping for some practical
answers, to see if i consider should setting out on this.
>
> it seems like it would be relatively easy to detach the PSU from the
CS80, and make it an external unit. im assuming that most(if not all) of
the reknowned pitch instability/temperature issues were due to the
massive PSU/input transformer.
 
RJ - thanks for bringing up an interesting topic.  I'd really like to
see other techy-oriented people to suggest things like this or talk
about mods they've done/seen/thought of.  That said, I'm having trouble
with the remote power supply for a few reasons.  First, why?  I don't
agree that the PS is the source of tuning problems. To enter rant mode
for a second, the whole "cs80s have unstable tuning" is blown way out of
proportion. It was quoted in a couple of articles and is now considered
gospel. Given that, I think most tuning issues are from heat and most
noticeable in earlier CS80s with the older VCO chips.
 
> after seeing this firsthand, i see there are just two harnesses and a
ground wire that connect to the rest of the synth. it seems like it
would be pretty easy to take the PSU out, install 1 or 2 connectors to
adapt the harnesses to, and build an external box for the PSU. there
cant be more than 16-18 total harness pins for the rails of the PSU. by
now, im sure every cs80 in existence is a studio unit, and this wouldnt
be too inconvenient, and could potentially help the stability. of
course, the connector would have to be a screw-in type that could be
well secured to the chassis.
 
I have to agree that voltage drop will kill you.  The supplies have
sense lines, so you'd need three wires for each voltage: a big hot, a
big ground (you'd need separate grounds to have the sensing work right -
which might require modifying the PS), and a sense line.  Lots of big
wires!  Ever see the remote PS in the Kurzweil K250?  Huge cable, lots
of pins, connector was big (and probably expensive).
 
What might work is remoting the main PS, but keeping the regulators in
the case.  But then again, why?  To make it lighter :^)

 David