Yamaha CS80

Sounds great David! Keep us posted. Then when you finish you'll be all 
ready to work on mine!  ; )


Stephen Teller
Stephen Teller Music
805/480-9614
s.teller@...


On Oct 20, 2004, at 10:17 AM, yamahacs80@yahoogroups.com wrote:

> Subject: Re: Another CS-80 on the overhaul bench
>
>
> Hi all.
>
> I'm getting into refurbishing/fixing my CS-80 and thought some people
> would be interested in seeing what's involved.  I created an album in
> the Photos page called CS80 renovation.
>
> There's a picture labeled "Here's where it's happening!", which shows
> a corner of my TV room, converted to a repair shop.  I picked up a
> Weller desoldering station and Beckman Oscilloscope very cheap on
> eBay.  On the floor, you can see the box from Digikey where I got all
> the CMOS chips, IC sockets, and capacitors.
>
> There are also three pics of the TSB boards.  These are the first I'm
> upgrading.  They multiplex the aftertouch voltages from the keyboard.
>  I desoldered the five 4051 chips and installed machined sockets.  One
> semi-problem: the holes between the rows of pins are supposed to be
> exactly 0.3" apart. Well, they're slightly wider.  This isn't a
> problem with the chips, since the leads are flexible.  However, it
> made putting in the sockets a pain. Also, since the socket pins were
> forces into a slight angle, it made getting the new 4051s in
> difficult.  For the last few, I cut the sockets in half and inserted
> each row separately.  This made everything much easier.
>
> In the pic "Back of upgraded TSB board", you can see the little bypass
> caps I put on the 4051s.  The 4051s are different than most digital
> CMOS parts since they're analog switches.  They have a negative supply
> (-6.5v), and two positive supplies, one for digital and one for
> analog.  They are both tied to +8.5v.  The minimal bypassing was
> between these two supplies. I added caps from each to ground.  The
> ones that reached a longer distance are covered in red heat-shrink 
> tubing.
>
> In pic "TSB board after upgrade" you can see the 4051s in their
> sockets.  In the top, left corner you can also see two bigger, blue
> capacitors I added to bypass the +8.5 and -6.5 supplied where they
> enter the board (the red and green wires in the corners).
>
> One last weird thing: the two TSB boards in my CS80 are slightly
> different versions!  I think they're electronically identical, but the
> PC boards are a bit different.  After I put the caps on the first
> board I was just going to put them in the same places on the second
> board.  When I tried to do that, I couldn't find some of the reference
> points I was looking for. I thought I was going blind, but then
> realized the differences.
>
> The good part is that everything still works after all the soldering
> (which is really good since it was all working before I started)!
>
> Now I'm on to the other boards.
>
>  David
>