CS-80 Calibration Part 10: Portamento, Ribbon and Keyboard Control

This part requires one more time to lift the keyboard. If you have the Kenton Midi Interface installed be careful not to break its two long legs at the rear when lifting it up to get to the KAS board.

Portamento/Glissando

There is an error in the adjustment procedure manual, IC24 is labelled wrong as IC2. The IC24 we are looking for is actually on the upper left corner of the KAS board.

Measuring pin #6 is impossible without taking the board out, so I was looking for something nearby that can be used, fortunately there is a jumper which is directly connected to pin #6.

IC24 on KAS and measuring point

Adjusting is easy and it was the first time that the ping pong between two VR trimpots was working smooth without being jumpy or giving me a headache.

Ribbon Controller

Adjusting the Ribbon Controller is done on the BA board.

BA Board

The idea is to put your finger on the middle of it and then do the adjustment, staying within a certain tolerance level. This is kind of funny, because where the heck is the exact middle of the ribbon? 

Ribbon from back side

So, the middle is somewhere in the middle, but every time I pressed it, the values differed. Even wiggling the fingers really slightly will have an impact with a bunch of ms. From the middle to the right the trimpot will shift about 25mV. So if you press what you think is the middle and you see something like 75mV then what are you going to do? ;) Well, I moved my finger a little to get close to what the ribbon thinks is 0V and adjusted from there. 

The exact spot doesn't matter anyway. The good thing is, wherever I lay on my finger on the ribbon it will start pitching up or down relatively from that spot.

Keyboard Control

For adjusting the two KBC boards are required to be taken out from the cardholder rail.

KBC Board with that cool white IC

Adjusting KBC1 was easy and done fast. KBC2, well, not that fast. I'm not sure if the given values for KBC2 adjustments in the manual are correct. I cannot get to +2.76V and -2.76V. With the trimpot full right I was seeing 2.7V. As the original reading is +2.66V I decided to go with that. It looks good, because if I move the lever in the opposite direction I also get something around that value. I updated this finding in the manual.

Continue to Part 11: Exp Curcuits and Output Amplifier