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Yamaha CS-15 synth restoration
Old 1st January 2010
  #1
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Don Solaris's Avatar
 
4 Reviews written
🎧 10 years
Yamaha CS-15 synth restoration

Yamaha CS-15 synth restoration


This is how typical synth restoration looks like. I recently bought CS-15 directly from Japan, but since this is 30 years old synth, full work was required.


Japan uses 100V. So first job was to buy and put new transformer inside and replace capacitors in power regulator board. If you buy a stock 2x18V transformer it will most likely come with 4 connectors - yet CS-15 PSU board expects 3. In that case, you'll have to be creative, connect middle two into one and connect it to the middle one on the PSU board as i did. Apply isolating tape to each line individually then wrap together. Don't use cheap tape! It will open itself after a year.

To fix transformer, drill the bottom of the synth and insert transformer screw, then tight it firmly. As you can see i was lazy to drill, so i used another solution to fix it (so the wood remain untouched).

Important: European (230V) users, check the fuse if it is 250V. If not, replace with one. Also replace the block capacitor with the 300V one! Capacitor is hidden along the mains line that goes into transformer (yellow wire, far right side, on the pic).




Now remove all knobs and prepare unit for the shower. You'll find a lot of dirt here.




Remove all boards out.




This is still the best cleaning method i've found so far.




Synth boards out. Preparing to treat potentiometers with high pressure air compressor. After that i used a contact cleaning spray.

As of the faders, due to their larger exposure to dust and dirt (a lot of it falls in!) i had to disassemble them, open each and then go with the cleaning. I wash them in the sink using soap and hot water. It would not be a good idea to use contact cleaning spray on them as it will just make them more sticky thus less precise.




Boards put back and a little bit more cleaning.




Calibration. Took me an hour to complete it.
Old 1st January 2010
  #2
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Don Solaris's Avatar
 
4 Reviews written
🎧 10 years
...continued from previous post



Calibrating the LFO on oscilloscope. Setting it to precisely 100 Hz. One of the nicer things on the CS-15 is having the audio rate LFO. This can be modified for kHz range, but more on that later.




Old capacitors heading toward trash can.




Finished baby.
Old 12th November 2012
  #3
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natrixgli's Avatar
 
🎧 10 years
This was one of my first synths, very unique sounding. The filter won't self resonate, but (and this is probably horrible and you should never do it) if you send the low output into the audio input it will howl.
Old 12th November 2012
  #4
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gordonmerrick's Avatar
 
🎧 10 years
Beautiful synth, Don.

Edit: Ha. I just noticed the date on the original post. Still have the synth?
Old 12th November 2012
  #5
Lives for gear
 
🎧 10 years
The cs15 sound really cuts through on a mix. Great for leads. Awesome rebuild here
Old 12th November 2012 | Show parent
  #6
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Rooftree's Avatar
 
🎧 10 years
Quote:
Originally Posted by natrixgli ➑️
. . . (and this is probably horrible and you should never do it) if you send the low output into the audio input it will howl.
Actually, you SHOULD do this. It works great. You can control the amount of distortion and feedback with the EXT IN knob.
Old 12th November 2012 | Show parent
  #7
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Don Solaris's Avatar
 
4 Reviews written
🎧 10 years
Quote:
Originally Posted by natrixgli ➑️
This was one of my first synths, very unique sounding. The filter won't self resonate, but (and this is probably horrible and you should never do it) if you send the low output into the audio input it will howl.
Where the hell did you found this thread?


Quote:
Originally Posted by gordonmerrick ➑️
Still have the synth?
You know the default GS answer.

Yes.
Old 13th November 2012
  #8
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Rob Ocelot's Avatar
 
🎧 10 years
I love the CS monos but to anyone considering Kenton's filter CV upgrade I'd suggest you pass -- not that it's good but you'll be pissed when you find that the 'upgrade' is nothing but an 1/8" socket, a couple of wires, and a photocopy of the relevant page of the service manual showing where to hook them up.

That's one very expensive socket. I hear photocopies aren't cheap either.
Old 13th November 2012
  #9
IEC
Gear Maniac
 
IEC's Avatar
 
🎧 5 years
hi there, mr don solaris i bought a cs-15 from japan 6 months ago, and got them to install the 'don solaris mods' i found on the net... nice to meet the man behind the mods
Old 13th November 2012
  #10
KT1
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KT1's Avatar
 
🎧 10 years
Nice work don. :thumbup:

Sent from my HTC Desire S
Old 3rd March 2013
  #11
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adhmzaiusz's Avatar
 
🎧 10 years
Hello
I just recently got a 100v CS15 myself, and while I've done many repairs, the whole transformer replacement business is something I don't quite understand yet. What should I be asking for in my electronics shop? Is there a certain voltage that needs to come out the other side that goes to the power supply? Can't find info on that in the service manual.
Old 3rd March 2013 | Show parent
  #12
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Don Solaris's Avatar
 
4 Reviews written
🎧 10 years
Quote:
Originally Posted by adhmzaiusz ➑️
Can't find info on that in the service manual.
You don't have to. It's written in the first post.
Old 21st March 2013
  #13
Registered User
 
🎧 5 years
Did you only replace the electrolytic caps? Any specific ones to choose?
Old 21st March 2013 | Show parent
  #14
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Don Solaris's Avatar
 
4 Reviews written
🎧 10 years
Quote:
Originally Posted by Hallu ➑️
Did you only replace the electrolytic caps? Any specific ones to choose?
Yes. I use those that are NOT produced in PRC.
Old 23rd March 2013
  #15
Registered User
 
🎧 5 years
I made a separate thread discussing this in general, but I just found these MIDImplant chips and I think its a very exciting option for specifically CS-15 owners

Small sized MIDI2CV, dual channel

If I'm reading the details of this mod right, it has two separate CV outputs. Theoretically, this would allow for both oscillators to be controlled independently by MIDI on a single mod, for much less of a price than a single Kenton CV->MIDI controller. This seems like the easiest way to unlock the 15's potential for sequencing with modern gear, right? Am I missing anything?
Old 23rd March 2013 | Show parent
  #16
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Rob Ocelot's Avatar
 
🎧 10 years
Quote:
Originally Posted by Hallu ➑️
I made a separate thread discussing this in general, but I just found these MIDImplant chips and I think its a very exciting option for specifically CS-15 owners

Small sized MIDI2CV, dual channel

If I'm reading the details of this mod right, it has two separate CV outputs. Theoretically, this would allow for both oscillators to be controlled independently by MIDI on a single mod, for much less of a price than a single Kenton CV->MIDI controller. This seems like the easiest way to unlock the 15's potential for sequencing with modern gear, right? Am I missing anything?
Nice find!

The only caveat that I see is that you cant set CV1 and CV2 to both be pitch on the same MIDI channel (and thus play the CS-15 like a duophonic synth from one keyboard). If you set CV1 to be note pitch then CV2 automatically is routed from MIDI velocity. In this configuration it's probably meant for CV2 to be routed to a filter rather than pitch, much like the auxiliary CV channel on a Kenton unit.

If you assign two different channels to note pitch each for CV1 and CV2 then you could play both oscillators separately from a sequencer. You'd need to do some fancy MIDI routing to get it to play duophonically from one keyboard. Doable, but not easy.
Old 23rd March 2013
  #17
Registered User
 
🎧 5 years
I'm okay with not using the same MIDI channel. The other caveat is that it seems like only one trigger output. It'd still make things more flexible than other options, and for a song that has a consistent bass rhythm I could see it working.... maybe we should email the designers???
Old 23rd March 2013
  #18
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Rob Ocelot's Avatar
 
🎧 10 years
It looks like it's quite flexible. I bet the author could write a custom firmware for you, or even better: write a program that generates a custom firmware with the routings you want.
Old 23rd March 2013 | Show parent
  #19
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atma's Avatar
 
🎧 15 years
awesome! such an incredible synth, i've always wanted one. they seem to be one of the few great analogs left that can be found cheap. i wish i were a real man and could restore electronics :(
Old 28th March 2013
  #20
Registered User
 
🎧 5 years
I am addicted to checking in with the DHL tracking info on my CS-15. Should be here in a few days

Also, the MIDImplant chip DOES have two gate outputs. This is hands down the best MIDI option for the CS-15 - emailing the company about availability. If I can undo the wiring for the cv/gate outputs and put those directly into the chip then this will be the easiest retrofit ever methinks.
Old 28th March 2013
  #21
Lives for gear
 
🎧 10 years
how long did the whole procedure take you?
Old 28th March 2013 | Show parent
  #22
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Don Solaris's Avatar
 
4 Reviews written
🎧 10 years
Quote:
Originally Posted by minime123 ➑️
how long did the whole procedure take you?
Given i have a regular day job, and i'm doing this during spare time only, the answer to this question would be unreliable. IIRC: one week.
Old 28th March 2013
  #23
Gear Maniac
 
🎧 5 years
Such a beautiful synthesizer. Nice work don
Old 31st March 2013
  #24
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🎧 10 years
maybe a better question would be...
how many hours would you say you invested in this restoration?
Old 31st March 2013
  #25
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crystalmsc's Avatar
 
🎧 5 years
That's a sweet victory..congrats!
Old 8th October 2015
  #26
Here for the gear
 
5 Reviews written
🎧 5 years
Does anyone know the difficulty in fixing key/trigger issues. I am wondering how difficult it will be to have a tech order parts. Just got a nice cs15, very clean outside and inside HOWEVER it seems my last few keys are finicky. Sometimes they trigger, sometimes they need more pressure, sustaining is a crapshoot at best.

Anyone have similar issues or know what might be going wrong? I am also noticing that my VCO2 does not produce a tone, but rather a thin whispy output regardless of octave/shape/filter settings. I get how VC01 routes with mix 1 and 2, but is VCO2 always like this or is mine having issues??

Sorry to revive this thread, but it looks like some smart people have some good advice on a related topic. Thanks again!
Old 9th October 2015
  #27
Lives for gear
 
🎧 5 years
I have 2 CS15s that both have triggering issues, so guess it is unfortunately a common problem with these beauties.

Been searching through my old posts - someone responded to me with some good advice the last time I mentioned this on GS, but sorry, can't find the thread now. Anyway seem to remember a it including a link to someone who was making replacement boards for the trigger section. Didn't look that deeply into it as I live fairly close to Modeless Factory, so thinking I'll run them them down to him at some point as I'm considering some other mods too, but was good to know there was at least some alternative support out there. Sorry don't recall costs either, but in general get the impression that these are generally quite repairable anyway.

Specific to your problem though, you might have a look inside yourself and see if it isn't just a dirty contact issue or something - opening it up and pulling the keyboard apart is very logical and easy... Service manual is also readily available...
Old 9th October 2015
  #28
Lives for gear
 
🎧 5 years
Aha! found the thread ( @ Starspawn is my hero):
https://gearspace.com/board/electron...l?ref=gearPage

Seems the boards are more of a DIY thing than I remembered.
Old 13th April 2019
  #29
Here for the gear
 
Quote:
Originally Posted by Don Solaris ➑️
Yamaha CS-15 synth restoration


This is how typical synth restoration looks like. I recently bought CS-15 directly from Japan, but since this is 30 years old synth, full work was required.

Japan uses 100V. So first job was to buy and put new transformer inside and replace capacitors in power regulator board. If you buy a stock 2x18V transformer it will most likely come with 4 connectors - yet CS-15 PSU board expects 3. In that case, you'll have to be creative, connect middle two into one and connect it to the middle one on the PSU board as i did. Apply isolating tape to each line individually then wrap together. Don't use cheap tape! It will open itself after a year.

To fix transformer, drill the bottom of the synth and insert transformer screw, then tight it firmly. As you can see i was lazy to drill, so i used another solution to fix it (so the wood remain untouched).

Important: European (230V) users, check the fuse if it is 250V. If not, replace with one. Also replace the block capacitor with the 300V one! Capacitor is hidden along the mains line that goes into transformer (yellow wire, far right side, on the pic).

Don Solaris, what was the VA / current output spec for your 2x18V toroidal transformer replacement?
Old 14th April 2019 | Show parent
  #30
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Don Solaris's Avatar
 
4 Reviews written
🎧 10 years
Quote:
Originally Posted by amk1 ➑️
Don Solaris, what was the VA / current output spec for your 2x18V toroidal transformer replacement?
I don't have Yamaha CS-15 anymore. :(

I sold it to Maison Vague. I might have to buy it back.

To answer your question: Transformer wattage is calculated by the specified wattage written on the back of the unit +20%. Technically speaking transformer will be labeled in VA units and not Watts, but that's another topic. The point is, in your case 1 Watt = 1 VA.
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