CS-80 Calibration Part 12: Done Done Done

The final step was to disconnect all GND cables and move back the card holder rail back in its lower position (while trying not to rattle the rail too much to prevent trimpots adjustments jumping) and finally close the lid and listen to the result of the endless hours I have been putting into it during the last few weeks.

Lid closed, ready for testing

So, how was it? I was impressed to say the least. For the first time I have a CS-80 that sounds playable in the way it was designed to sound. No different envelope timings anymore, no wrong aftertouch/velocity behaviour, nothing odd. It just gave me goose bumps playing on it (especially with that Vangelis reverb).

As with every project there are victims. But thanks goodness, the list is small, especially when you see all those endless numbers of rare custom chips on all those boards while you are adjusting... You get the picture.

I had to say good bye to:

• One IG00150 VCO II for ring modulator, replaced by one from the Tremolo/Chorus)
• One TA7504M Opamp on one M-Board, replaced by a UA741CH.

Aside from that I am kind of wondering about the many errors in the adjustment manual that leave you sometimes puzzled what to do. I also wonder why there are no revisions of that adjustment manual.

I would like to know how many CS-80 are actually calibrated to "well, sounds good, going to leave it that way" when trying to work around erroneous specs instructions. Also, interferences between trimpots have nowhere been taken into account inside the manual. The VCF level adjustment was giving me a headache because of this. And and and...

However, hitting notes on the keyboard when it sounds right will make forgetting about all that calibration grief.

Aftermath

Of course, after adjusting so many parameters and despite double/tripple checking the results after each step there were issues which required to open the lid again and do some rework:

• Using the VCO aftertouch modulation triggered on one voice the full aftertouch level by just slightly moving the lever. After checking the board and looking for some problems (after all it was the exact same voice where I had this factory QA fail problem) it turned out, the trimpot level was in the wrong position. I guess I may have moved the wrong one by accident after I finished that step

• I had to retune all voice boards. A few were off about 7cents, one was even 12cent off. I think it is some interference between all the settings. Or maybe jumpy trimpots caused it, what do I know. :)

• The VCA levels also were not properly valid on some boards. Only slightly out of specs, but still not correct, so had to do that again too.

• Two voice boards acted a little different which I have to examine closer to find out what is wrong there, one day... One voice board's VCOs sounds slightly nasal too.

That's it so far. Will have to see if more calibration aftermaths will come up while I use it.

Project Completion

I hope the information provided is somewhat helpful for you. A lot of time went into calibration and documentation. I expected a weekend or another to fully calibrate the CS-80 when I started. That was naive, it took me almost 4 weeks(with some breaks). If I would to have to do it again, I guess it would take me two weekends (naive again?).

If you have any corrections, would like something to be added or anything else, let me know. Also if you have a spare ribbon or M-board and want to get rid of it, I wouldn't mind to take it over.