Yamaha CS80

Hi,
Don't forget that the lower rail on which the boards are screwed is at a voltage of +15V !
If what you want is only to no longer listen to this voice board, why not just unsolder its output O (33) ? But be sure to leave the two wires soldered together or you won't be able to listen to the boards located to the left of the one you want to skip.

Hello Joachim, Thank you for those explanations. Indeed, i forgot about the +rail voltage.But i guess i can adress that with some cardboard put between the rail and the tail connection of the board?
Actually my primary intend was to simply disconnect the output as you suggest, but i realized today that i could also disconnect one of the last voice M board from the system to get a few spares and then being able to isolate the bad IC in the other voice card, much quicker than hunting for one online, or locally here in Italy.
So i guess it means that i would need to properly disconnect this board from any supply -15/+15v voltage, but even if i manage to do so, what about the other 'communication' connection (with SH, KAS...)? Is it safe to let a voice card in the system, even though it is decoupled from the supply voltage ONLY?
Or should i completely unsolder all the wires from it?
I saw a post here of David Rogoff talking about jumpers in the KAS... i dont know how to locate those jumpers yet, but is is the proper procedure?

Thank you

Oh btw Joachim, i think you did a great job with the interactive diagram about the CS80, congrats and thank you for this!

I just read the post of David you mention. By a "jumper" I think he did not mean a physical jumper, but a wire to be added between +8.5 and  the resistor at pin40 of IC1 (YM26600). By the way, beware that in the service manual of the CS80, the numbering of the pins of IC1 and IC2 on the KAS board (page 5) is erroneously done the other way round ! Pin 40 is the one labelled 1 and vice versa.
So, you'll have to unsolder the extremity of the 22k resistor at pin 40 (the one pointing toward IC2) and then solder a wire between this unsoldered extremity and the +8.5V point of the KAS board located close.
I posted an excerpt of the KAS diagram where this is illustrated here:
https://groups.yahoo.com/neo/groups/yamahacs80/photos/albums/1349051368

As for unsoldering the whole board, that is something I would try to avoid. Just swap the defective component between the M-board where it is now and the M-18 or M-28.

Thank you Joachim for such precise explanations, i couldnt expect that much:-)
Now i understand more the meaning of the 'pronouncing mode' mentionned in the pin terminal description of LSI YM26600.(+8.5v=7 sounds instead of 8).
So i unsoldered the 22k resistor as you described, streched its leg a bit to reach the +8.5v connection close to IC2, and resoldered it there.
Now i get ready to swap some parts from M28, and hopefully get the CS80 fully working soon, running on 7 voices only, more than enough for now, at least before finding new spares.

Big thanks for the help,

Cheers

Hi If you're interested I have a voice card for the cs80 listed on e-bay and it's

Thank you Tim, indeed it may be interesting.For now i found only 2 IC damaged, but if i find more than that in the end ,i will let you know :-)

Regards