Yamaha CS-50 Calibration

[syntheticsolutions]

Hey all!

I recently acquired a minty CS-50 and am pleased to say it is fully working and complete.

It is however, in need of some serious calibration. Each of the 4 voices seems to have a different level on the VCA and the pitch scaling on the voices is far off enough to render it unusable.

My question is this... Is the calibration process on these machines as simple as others where the correct values can be reached by calibrating trim pots on the voice boards or are they more involved?

I have a tech that is readily available who is well versed in general analogue synth maintenance and tuning however even he assumed it may be out of his depth.

I have another tech that could take a look but I am looking at a hefty waiting time on him. Not sure I can part with this beauty for 6 months before getting to enjoy it again.

If anyone has some insight into what is involved in the calibration and tuning process on these beasts, I would love to hear it.

Thanks in advance,

Ryan

[Yekuku]

Hi Ryan,
calibrating the cs-50 is pretty straight-forward , if you have similar experience.
Be sure to check calibrating instructions for CS-60 and CS-80 too.
The only real problem is how to identify the voice card that is active.
I used the yamaha cs-80 instructions to identify the active voice card by touching the VR3 trimmer and never had any problem.
BUT, what Oldcrow says is right so be aware :

"Touch master boards (#1 ~ #7) lightly on the foil side of the boards in the area of the blue pot (VR3) at the upper front side of the circuit board (see Fig. 4)." DO NOT DO THIS!! You will kill the CMOS chips on the SH board if any electrostatic charge leaves your fingers and conducts from the M board through the wires to the SH board. All M boards are connected to the SH board both for pitch control and triggering. I used an ESD wrist-strap while doing this and still managed to kill the SH board on my CS-80. Easy enough to repair, but annoying all the same.

The safest way to determine which pair of M boards is sounding is to turn the power off for 5 seconds then back on. The first key played will always sound voice #1. 2nd key is voice 2, etc. For voice #8, press a key 4 times, holding the key down the 4th time. then hold down the desired key to sound for #8 and release the first key. Voice #8 is now sounding.

[syntheticsolutions]

Hi Ryan,
calibrating the cs-50 is pretty straight-forward , if you have similar experience.
Be sure to check calibrating instructions for CS-60 and CS-80 too.
The only real problem is how to identify the voice card that is active.
I used the yamaha cs-80 instructions to identify the active voice card by touching the VR3 trimmer and never had any problem.
BUT, what Oldcrow says is right so be aware :

"Touch master boards (#1 ~ #7) lightly on the foil side of the boards in the area of the blue pot (VR3) at the upper front side of the circuit board (see Fig. 4)." DO NOT DO THIS!! You will kill the CMOS chips on the SH board if any electrostatic charge leaves your fingers and conducts from the M board through the wires to the SH board. All M boards are connected to the SH board both for pitch control and triggering. I used an ESD wrist-strap while doing this and still managed to kill the SH board on my CS-80. Easy enough to repair, but annoying all the same.

The safest way to determine which pair of M boards is sounding is to turn the power off for 5 seconds then back on. The first key played will always sound voice #1. 2nd key is voice 2, etc. For voice #8, press a key 4 times, holding the key down the 4th time. then hold down the desired key to sound for #8 and release the first key. Voice #8 is now sounding.

Thanks so much for this info. It really helped a lot.

The task wasn't half as bad as I was expecting and managed to get it all tuned and scaled within an hour and half. Very happy to be able to hear what this machine is capable of without shrieking at the tuning.

I conducted the tuning procedure by simply switching the synth on and off in order to reset the voice count, just to be extra safe. whilst slightly tedious, it was no real issue.

The only problem I am left with is that voice 3 is seemingly lower in output volume than the other voices. I was hoping this could be calibrated via a trim pot relative to the VCA however I can't find any pin point information in the service manual. Do you happen to know if there is such a trim pot and what VR number it is if so?

Thanks again, super helpful info.

Ryan

[Yekuku]

Post edit, please delete.

[Yekuku]

Good work Ryan!
I remember having to unsolder one wire to calibrate the VCA but my memory does not serve me right .
This should help:


Calibration of voice cards:
https://mfoxhd.blogspot.com/2016/01/cal ... oards.html

Good luck !