Archive of the former Yahoo!Groups mailing list: Yamaha CS80

Hi Folks,


I have build an circuit of the CS80 VCO chip like showed in the Service manual.
First i build it with LTSpice after some troubleshooting i build the circuit on breadboard

and it works. I do some measurements with the following results:

CV Frequency
1 V 642 HZ
2 V 1253 Hz
4 V 2381 Hz
8 V 4360 Hz

if I double the Control Voltage the Frequncy should also have the double value.
My VCO don't do this. I think it is of course the tau Value(30µs) of the Monoflop.
T = tau + I. The 3Oµs Peak is one "secret" of the VCO but how do the make this in their

Chip?
It would be great if someone can give some tips or measurements of a real Yamaha IG00153

chip.

What is the maximal CV at the input of the VCO
What happens if the Tuning Knob on the panel has the max Value this means 6 Volts at the Note Voltage DAC and you make a high Pitchbend with the Ribbon control with the highest c depressed?
What is the Range of the Ribbon Control.

Sorry for this silly Questions but i don't owe a real CS80. I played one in the 80s.


Thanks

Oliver