Yamaha CS-10, EG issue

[DanieleRossi]

Hello everyone!!

This my first topic, so, glad to meet you all!

It looks like i have some issue with envelope generator on my CS-10, it only plays a continuous note, and sometimes it only works on HOLD position. So my suspects all goes to the EG not working anymore for some unknown reasons...

I was wondering if you have any easy thing I should be checking in the first place, like potentiometers, condensers or resitors on the circuitboard? I hope it is not the microchip because it costs like 80£...

I really just need some hint to star with.

Many thanks for your help!
Best

Dan

[madtheory]

Have you tried this:
viewtopic.php?f=5&t=112636&p=819485#p819485

Also, the switches get dirty. Caig Deoxit will solve that. You can try spray in from the front panel. Failing that, IIRC you will have to completely dismantle it to access the back of the switch.

[DanieleRossi]

Hello madtheory,

many thanks for your answer,
i bought the deoxidizer you suggest and I'll have a go with it

I'm sure it is not a matter of settings because it has been like that for like 10years now and i tried all possible combinations...
I already dismantled the synth and checked the circuit for any evident issue with no results.
I guess I'll check the circuit with a multimeter next time

cheers!
Dan

[madtheory]

OK, I hear you but my money is still on the settings in the link... if not, I'd seriously consider going to a qualified tech, because this synth is worth good money these days.

But failing that next steps:

1. Check if the switch works properly, it could be that it has failed completely.
2. Check for shorts and dry joints around the EG circuitry.
3. Get the service manual and IC data sheets (Yamaha published both).
4. Go through the circuit and locate a faulty component. Hopefully the schematic shows test points and voltage levels, and/ or you can figure those out from the data sheets. Most likely would be a dead capacitor, or as you say the EG chip. They are all old CMOS so will be decaying already. But could be any component there, check them all including resistors.

[DanieleRossi]

Thanks Madtheory, really appreciate your help!

Yeah i know i should't make any experiment on this stuff but i'm not sure it is worth the money, time and effort of getting it fixed by a technician...

I'm going to try some of this stuff and I'll let you know what happened

Cheers!
Dan

[DanieleRossi]

So.... a few updates...

I've been dismantling the EG board yesterday, sprayed the deox everywhere it was needed,
than I i unwelded and tested most of the capacitors and they where all ok....

put it back into the case and tested and of course, same deal, nothing changed

but, i notice that whenever i swiched from ext to m or s mode, the trigger light would turn on, and the sound would get affected accordingly to the parameters; therfore, my deduction is that the trigger signal from the keyboard is cut of at some point in the circuit but the EG itself is still functional. I think it makes sense.

I will keep making some more tests in the next days.

Cheers!!

[madtheory]

Interesting! Maybe the external audio trigger level circuit is sending a wrong voltage? I don't think the CV trigger socket would be the issue, IIRC that does not bypass the keyboard, it adds to it.