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• CS-15 Disassembly

  Quinn • 08/12/2025 at 17:38 • 0 comments

  Nothing super complicated in disassembly, but adding a lot of pictures for reference in reassembly.

  Overall it's really well constructed for serviceability which is great.  There are a couple nuisances like the handful of wires which are directly soldered, instead of using connectors, that have to be removed to remove the board/module.  They are well labeled though.

  The service manual does a good explanation of the basic opening, as well as exploded parts view.

  Many of the knobs were too tight to remove by hand.  Not wanting to scratch them further, I used this trick using some old credit cards.  These are not real credit cards, but rather the fake ones that are sometimes sent in the mail as advertising.  Most of them now are cardboard, but they used to be all plastic.  I just cut a few with a notch as shown, with the notch wide enough to go around the nut.  First I put two under, then I slide a third (or more) between them. This forces the knob up from the bottom sides, without scratching the panel or knob.  If you don't have any of these, and sort of firm think plastic like this should work.

  I take note that there are two sizes of nuts.  The larger are for the rotary switches.

  I found it surprising that they had placed lock washers between the pot on the inside and the inside of the panel.  This of course meant they all fell off when removing the board.  This does nothing towards keeping the nut secure.  With some analysis, I think they are using them as spacers to make the rotary pots/switches match the height of the plate on top of the sliders.

  A bunch of documentation pictures follow in case they are ever helpful in the future.

  Details of the left board, CPA.

  Top:

  
  

  Detailed views, left to right:

  
  

  Bottom

  Detailed views, left to right

  Below also shows the pads for the LFO LED, all the way on the left, labeled RE and BL. (It's been unsoldered at this point)

  Details of the right board, CPB

  Top

  Detailed views, left to right 

  Bottom

  Detailed views, left to right 

  Below also shows the pads for the EG1 and EG2 LEDs, left of the openings, labeled RE and BL

  Details of wiring/connections

  CPA

  Heres one soldered wire, a ground.  As it's in the loom, I suspect factory done.  That they needed another ground and didn't want to use a larger connector 

  CPB

  Keyboard 

  SSK

  Here's another set of soldered wires, for the power LED

  Rear panel

  AC Inlet

  The device in the middle below is identified in the service manual as a 2p terminal.  (It's a 3p for the G/General export variant)

• CS-15 Modification Analysis

  Quinn • 07/28/2025 at 20:59 • 0 comments

  Inside

  There are 3 modifications someone previously did.  Aside from maybe the LFO speed select, I'm not a fan of the others and plan on undoing them.

  A quick look inside also shows why the EG leds don't work: they are unsoldered.  Not sure if that is because someone wanted that, or if they did so just to remove the board and didn't reconnect.  Hopefully an easy fix.

  Modification 1

  This is labeled on the inside of the case as "LFO", and just looks to switch in a resistor on the LFO Speed pot between the wiper/output and the +15 rail.  Unless there is another part to the mod, this wouldn't increase the maximum frequency, just give finer control at the high side.  Will want to look more when the board is pulled.

  Modification 2

  This is labeled on the inside of the case "Noise to VCF2".  This cuts the trace from the output of PVR 20, the noise pot in Mixer 1.  When the switch is in the down position, that output is instead connecting the output of Mixer 2.  When the switch is in the upper position, the outputs of Mixer 1 and Mixer 2 are combined.

  This is a strange mod which doesn't make a lot of sense.  I wonder if it was done wrong.  For instance if the two white wires on the switch were reversed, it would be a more logical function of just changing which mixer the noise pot is connected to.  Definitely want to remove this mod.

  Modification 3

  This is labeled "Filters - Series" on the inside of the case.  A jumper on the top side is cut to implement this in addition to the switch.  In the down position, it should restore that jumper.  In the up position, it takes the output of PSW32, which is the output of VCF 2, and feeds it to  the input of VCF 1. The input to VCA 2 is left open.

  This doesn't seem to align with my prior testing, so after reverting it I'll need to do testing again to see if something else is wrong.

  
  

• Yamaha CS-15 Initial Evaluation

  Quinn • 07/28/2025 at 20:36 • 0 comments

  Picking this back up with that Yamaha CS-15.

  Documentation 

  Thankfully the key documentation is easily available and attached to this project.  Not much else is needed aside from possibly finding some datasheets if needed 

  • Service Manual
  • Owners Manual

  Current State

  Functional testing 

  Doing a bunch of testing, here are the notes of things needing attention 

  • There are 3 mods with switches on the back panel that need to be addressed
    • 1: Switch down seems default.  Switch up increases the LFO frequency 
    • 2: Switch down seems default. Switch up seems to connect the output of Mixer 2 to the input of VCF 1
    • 3: is less clear.  It's impacting routing. Down seems to change noise, routing it to VCA2, and doubles the level of VCO 1.  Up seems to disable the output of Mixer 2 so it doesn't go anywhere 
  • EG1 and EG2 leds don't work
  • Pots and switches to clean
    • Mixer 2, VCO 1 and VCO 2 pots
    • VCF 1, LFO Mod and EG Depth pots
    • VCA 1, EG Depth pots
    • VCA 2, EG 1/2 switch
  • The main out, when outputting lower frequency square, the top/bottom droop, suggesting output cap is losing its capacitance.(Or was a limit to design)

  Photos

  Some photos of current state.  Needs a good amount of cleaning.

• Nord Modular Buttons and Pots

  Quinn • 03/22/2024 at 22:56 • 0 comments

  The buttons on this synth don't reliably work, and the pots are very gummy.

  Buttons

  Sometimes a button press will not be sensed, other times it will trigger multiple times.  Thankfully another owner had this issue and discussed taking them apart.  As stated by them, these are Marquardt series 6450 buttons.  They are well made, with wiping contacts and can be disassembled to be repaired.  You can still purchase them, but I figured it would be easier and much cheaper to try first to just clean them.

  I think their failing point isn't the wiping contact, but rather the pivot point between the flex contact and the fixed one.  They seem to corrode at that contact, suggesting incompatible metal types between them.  But not too difficult to repair.

  With the front panel board removed, the button tops can be removed by using something thin to press inwards on both sides.  As this has small plastic clips, I wouldn't pry or lever, but instead just press inwards.  I used a pair of tweezers and a thin flat blade screwdriver.

  As soon as you get the first one out you can more easily see how it works and quickly get the rest.  The picture below will help see how they are shaped.

  The flex contact can be easily removed with a pair of tweezers.  I pulled them all out and cleaned by putting them in a small jar with some contact cleaning spray, and swished them around.  This type of spray tends to get everywhere, so I keep some on this jar for finer application, or in this case just dropping all the contacts in.

  After a min or so of swishing, I just picked them out with tweezers and set to dry.

  The contacts in the base also needed to be cleaned.

  I used a small glue applicator bottle to put a couple drops of the contact cleaner on them, and brushed a little with these cleaning swabs.  Unlike "qtips", there is very little cotton on the tip so it fits in smaller areas and doesn't leave cotton threads that pull off.

  These are available on aliexpress for like 2$ for 300 delivered.

  After drying thoroughly, the flex contact can be reinstalled carefully with tweezers.  Put one end in, and slightly  bend it to get the other end as well.  I found it easiest with curved tweezers holding the zig zag part, lining in the curled end, then bending to get the sharp in on the contact.

  Here's a quick video

  Button cleaning

  While the button tops were off, I gave them and the knobs a good cleaning with soapy water and a nylon brush.

  Then let them dry.

  Pots

  The friction grease in the pots had gone gummy, such that turning them was quite a bit of friction.  While they still worked fine, the effort was tiring when trying to turn them a lot when being creative with the synth.

  This video is the best one I found which discusses the issue and how to fix it.  It's long, so you can skip by much of it, but I believe it is correct. (He correctly points to the issues with using contact cleaner on pots as well)

  The problem is that to do this one needs to disassemble the pots, and to do that with these, they would all have to be desoldered from the PCB.

  I decided it would be best to see what I can do without disassembling it and giving it a try.  If it isn't goo enough I can remove the board again and then go further.  Thankfully the front panel board is the easiest to remove.

  I used isopropyl alcohol, trying to wick it down between the shaft and the collar, rotating the knob back and forth to work it in.  This made a huge positive difference.  It remains to be seen if this will stay, or if they will gum up again.

  I'll readdress if I need to later.

  I did also look for replacements.  I was unable to find the original manufacturer, or direct alternates on pot vendors product lists, or in component distributors.  I can get the Nord resold ones through their regional representative, for 9$ each.  For 19...

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• Nord Modular Cleanup

  Quinn • 03/22/2024 at 21:44 • 0 comments

  The Nord modular needed some physical clean up as well as contact cleaning on the buttons and pots.

  Disassembly

  For more thorough cleaning I disassembled it. It is very serviceable and nicely built, so no problems here.

  First knobs were pulled off.  The small knobs are just friction fit and can be pulled.  The large encoder however you need to pop off the top cover and loosen the collet bolt to slide it off.

  Screws to remove the cover are mostly obvious, except for the one on the bottom.  The two side back have a plastic washer such that you could loosen and use it as a hinge, which sounds useful, but it hits the power cord so you can't actually open it far.  Just enough to disconnect the ribbon from the front panel before removing the side screws.

  (This is actually an after cleaning picture)

  Power board is obvious, just unplug the cables and a few screws.

  Main board is a little trickier, but no surprises. 1/4" jack nuts on the back along with obvious screws are removed to pull the main board.  You need to remove the extension and it's stand offs first.  Sadly the cable to the key bed doesn't have any connectors on either end, so have to be removed together.

  Key bed screws are on the bottom, sadly self tapping screws into the plastic so take care to reuse original threads when installing.

  Front panel board just has obvious screws.  The way it is built you don't need to unscrew all the pot nuts which is very convenient (though not as robust to impact on knobs).

  The AC cord is unfortunately affixed to the case.  I decided I didn't need to remove it.

  Key Removal

  The keys have springs on the back to hold them in and give proper movement.  The way these are designed you can just use an appropriate sized narrow screwdriver.  It should fit into the spring from the top, but not go through the smaller opening on the bottom.  You can simply push the screwdriver in, stretching the bottom down and out of the tab it is in.  The the key can come forward and out.  The springs are the same for all the keys.  To get the different needed force out of white vs black keys, the white ones a stretched further due to how the plastic is molded.

  The white keys are numbered in the plastic mold, which I noted in order to put back without having to figure out the order.  The black keys are not labeled, but are identical, which I've listed as B.  Note that there are some duplicates.

  Left side, C5, B, D6, B, E7, F1, B, G2, B, A3, B, B4, C5, B, D6, B, E7, F1, B, G2, B, A3, B, B4, C8, Right side

  The grime is much more obvious in this picture.

  Cleaning

  For the PCBs, I used a grounded antistatic mat, and just used a soft paint brush to clean off dust.  These didn't have any corrosion or other issues I needed to do.

  The keys are just plastic so I washed and scrubbed with a nylon brush and soapy water to get them all clean.  The dried up grease around the underside tab took a little extra effort but cleaned fine.  The dirty grease did leave some plastic discoloration, which didn't seem to be an issue.

  The case top and bottom also got soapy water cleaning, as did the power cable which was rather grimy  These also came out great.  There were a few scuffs in the powder coating, but not bad enough to bother with trying to repaint.

  Key bed was definitely the most grimy part.  While the rubber domes are available as a replacement, these seemed to be in fine shape so I didn't do much.  Underneath was plenty clean, so I didn't remove them and risk ripping them.  As it would have required a bunch of desolding to remove the PCB from the plastic frame, I opted to dry clean them together.  Some with the soft paint brush, and wiping with tissue was good enough.

  The keys have a...

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• Nord Modular Documentation

  Quinn • 03/22/2024 at 20:13 • 0 comments

  There is a lot of material out there for this synth.  Here are some links.  Will update as I find other noteworthy things.

  • Nord legacy product page
  • Nord OS, Software and Manual Downloads
  • Nord spare parts list 2023(PDF) and 2024. Covers all Nord products, but super helpful for looking up part numbers and seeing what parts are using across different synths. I suspect this is for their support and distribution channels only, as when I attempted to order parts I was directed to local distribution which was charging 4x or more vs what's in here.  I might try if they'll let me order front them as a local in Sweden if they'll sell for the listed prices.
  • Nord spare parts comparison chart 2024(PDF).  Handy for some part numbers and what boards are used in what synths
  • Advanced Programming Techniques for Modular Synthesizers(PDF), James Clark 2003
  • Wizoo Guide, Nord Modular 2nd edition (PDF), Peter Gorges, Len Sasso 2000.
  • Someone else's page with info on replacing the wheel encoder and fixing buttons. (It's fascinating that this person's front panel board has the same name(Manuel)  and date(98-10-14) on the test/assembly sticker)

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