Synth Restoration

Just doing some restoration on vintage synthesizers

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I picked up a couple vintage synthesizers to play around with last year and wanted to do some restoration/cleanup/repair on them.

I'm not an expert, nor a musician, just someone who wants to play around with some synths.

Various logs about the Synths

Nord Modular Key (G1)

This is the first generation Nord Modular, key version(as opposed to rack or micro modular version).  It is a DSP based analog modeling synthesizer which models modular synthesizer modules.  Design and patching is done on computer software, transfered live over a bidirectional control MIDI link.  Panel knobs, keys as well as external inputs and outputs are linked with the virtual modules in the software.  This one has the original Nord expansion board, which enables additional polyphony.

The software is solid, though retro given the 1998 era of the synth.  Windows and Mac OS 8/9 are officially supported, Mac OS X is unofficially through a beta version, and there is a third party Linux version as well.

The control MIDI link is picky on the MIDI adapter as it uses modes which are not supported on the cheaper adapters.  I ended up using a Roland UM-ONE MK2 as a cheap one didn't work.  The official Nord Modular manual basically says if it doesn't work, try a different adapter, less than ideal.

No true repair was needed on this, just restoration.

Project Logs

Ongoing logs:

Yamaha CS-15

This is a classic monophonic analog subtractive synthesizer.  It's sometimes refered to aa duophonic as it has two parallel chains which can be configured separately, but they are driven with the same CV/Trig from the keyboard so only one key can be played at a time.  Using external inputs they can be driven separately.

(I've played a bunch with this, but will document later as I do restore and repair)

Vintage Synth Explorer


Owners Manual

Service Manual

Project Logs

Ongoing logs:

  • (Link)


Advanced Programming Techniques for Modular Synthesizers, James Clark 2003

Adobe Portable Document Format - 19.23 MB - 03/22/2024 at 22:22



Yamaha CS-15 Service Manual

Adobe Portable Document Format - 6.52 MB - 03/22/2024 at 22:20


Adobe Portable Document Format - 4.33 MB - 03/22/2024 at 22:19



Nord Modular Brochure

Adobe Portable Document Format - 1.47 MB - 03/22/2024 at 22:18


Yamaha CS-15 Owners Manual.pdf

Yamaha CS-15 Owners Manual

Adobe Portable Document Format - 1.83 MB - 03/22/2024 at 22:17


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  • Nord Modular Buttons and Pots

    Quinn03/22/2024 at 22:56 0 comments

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


    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.


    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

    Quinn03/22/2024 at 21:44 0 comments

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


    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.


    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

    Quinn03/22/2024 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.

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