MATRIXSYNTH: 1977 YAMAHA CS60: Restoring the Power Supply

Wednesday, February 06, 2019

1977 YAMAHA CS60: Restoring the Power Supply


Published on Feb 6, 2019 Stephen Coker

"Restoring the 1977 Vintage YAMAHA CS60 Power Supply By Stephen Coker.

This is Part 1 in a Sequence of Videos i will Upload.

The Power Supply is in Tip-Top Condition, Maintaining Perfect Voltages on All 4 power Rails!

Checking the 4 Power rails even years Later still gives Perfect readings, to this day.

I've Restored the SUV, KAS, SH, KBC, SUB, M 1-8 and, PRE Boards along with many other parts of this Amazingly well Designed Classic Instrument.

I Replaced every Electrolytic Capacitor in the CS60 with the Highest Quality Available.

All Op Amps have been Updated.

Every CMOS chip is Replaced.

SH Board has been Completely Redone for Superior Stability.

All (M Cards) are Restored and I'm awaiting an order of potentiometer replacements of all the various values that have been difficult to source.

Some of the faults I've traced were tracked to the M board Calibration Potentiometers which, there are Well over 100 in the instrument, just for Calibrating the Voice cards.

Due to the Sheer amount of components that have to be replaced, it is Very timely and expensive to Restore these Classic Vintage Synthesizers but, they are worth every moment and, Dollar spent on them.

You have to be extremely careful working on the CS Polysynths for many reasons, to numerous to list here.

The YAMAHA CS Polyphonic Synthesisers are considered some of the most difficult to work on for many reasons.
One obvious being, the sheer amount of components but also, how the circuits interact with each other which cause troubleshooting and calibration to be more difficult then other Synths.

I've Rescued this instrument from a terrible death it had started years ago and, I'm extremely happy with how far I've come with it but, I still need to determine the origin of a few issues I'm having.

Troubleshooting can sometimes be tricky due to the Complexity of the Instrument and, Simply replacing IC's isn't a cost effective option.

The KAS Board exhibits some triggering of "Bad Notes" when I'm playing the instrument and my VCA Release is set halfway up or, more.
Using the Sustain Foot Pedal with a sustain release set halfway up or, more also causes the issue to manifest every once in awhile.

I'v tracked down all the Transistors used on the instrument what were difficult to find but, I've yet to install any yet. I will Replace the ones used on the KAS board to Rule out Transistors being the issue I'm having with "bad Notes" triggering.

Transistors creating the issue would be a "Best case scenario", Price wise because, if the issue is the Processor on the KAS board, it will be about $1,000 USD to replace. That would be a "worst case scenario"

Either way, i will have the instrument 100% Restored soon.

Thank You for Watching the Video."

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