I’m a chap of many interests, most of which are not going to get a mention here, but I’ve been buying and playing synths for over 20 years, and dabbling with DIY electronics for a little longer. When things started to go wrong with some of the vintage pieces I’d bought, I took the plunge and started to learn how to repair them. At first this was mostly stuff like crackling sliders or dodgy buttons, but since then I’ve managed to bring dead old keyboards and rack mounts back to life, have made one or two modifications to things, and have built my own equipment too – some from kits, some my own concoctions and adaptations.

All the information in these blog posts will be either available elsewhere on the internet (service notes, for example, which I will only link to if they are to be found easily for free, and not if they are of current commercial interest) or will be firmly based in my own experiments and experiences of working with specific items of music technology.

I hope this blog will be useful for those who wish to repair these same, or similar, pieces of equipment, or wish to learn something of their technical nature. I also hope it will be interesting, but I can’t guarantee you’ll stay awake through the whole thing…




EDIT: I now have a Twitter account specifically for this blog. You can get in touch via @nerdysynthdude 🙂

13 responses to “About”

  1. David says :

    Hello, saw you mention something about adjusting the gate for a CS5?
    Ive got a CS15 that I cant get a midimplant working on because even though the gate puts out +15 and 0V, the input to the key on still stays at 1.3V at TP19 and 24 when gated. The positive off gate is also lowered by about the same amount (to 13.6V)
    Theres positive voltage coming in there, would it help increasing the resistance?

    What did you do with the CS5?

    Best Regards

  2. Chris says :

    Hello! I was watching this video on having 2 oscillators and was wondering if you knew how I could then feed them out to my Mother-32? it seems to steal the patch points to make this happen but I’m imagining there’s a simple way to create an out from the breadboard?
    here’s a link to the video I’m referencing…

  3. Peter says :

    Thanks for your blog post “Moog Rogue: cleaning and repairing the dust shield”. Very informative and helpful info for the slider dust shield. As for the switch shields: Those rectangular pads may move/turn and suddenly you don’t have full coverage. Roland used round pads (looks like washers) and this works great – you can turn them any way and always have full coverage.

    • synthnerd says :

      You’re absolutely right, and I realised that as soon as I put the thing back together again! I left the Rogue ones as they were here, but started making round ones after that. I use small hand punches of various diameters to make the centre holes, the ones you tap with a hammer. Nice and easy, and allows a snug fit with full coverage of the panel hole.

      In fact, I improved the wiring on the transformer as well, but didn’t update the blog post. Perhaps it’s time to do that.

  4. Masuto masuto masuto says :

    Hi i modded my dr55 using your diagram-id like to make a post about it on my blog.. would it be ok to you?

  5. Cameron says :

    Hi, I noticed on a past forum you had the schematics for a Maplin 5600s, I wonder if you still have these available? If so, it would be great to get a copy.

    Look forward to your reply

    Kind regards


    • synthnerd says :

      Hi Cameron, thanks for your interest. My old 5600 build guide is an old photocopy of an old photocopy, and just about legible. I don’t have either a scanner or access to one right now, and no digital copy, so I’m afraid I can’t help at the moment. I believe the ETI 4600 shares a lot of DNA with the Maplin 3400 and 5600, but I’m not sure whether any of the sections are identical as I haven’t researched it. You can find some ETI info at https://encyclotronic.com/synthesizers/maplin/eti-4600-r1429/ – apologies, and good luck!

  6. Parker McAnnally says :

    Hey there, I’m in the process of rehabilitating a Korg ES-50 Lambda, and came across your blog, which is incredible. Here are the issues I’m trying to fix:

    In the percussive section:
    Piano is intermittent
    Harmonics is crackly and weak
    Tremolo weakens the signal

    In the ensemble section:
    Chorus is intermittent
    Strings 1 is intermittent
    Brass is slightly intermittent

    Intermittent, meaning sometimes you switch it on and it works, sometimes you switch it on and get nothing. Also, only the lower octave works – this has gone out over time, it used to be functional. I’ve got the Lambda opened up now, and any advice on how to fix these problems, or where to start, would be extremely appreciated. Either way, thanks a ton for having such a great resource of knowledge –


    • synthnerd says :

      Hi Parker, thanks for the compliment! It’s been a while since I looked at a Lambda, but from what you’re describing my first port of call would be to check the physical switches. It may be only that they need a good clean. All sounds pass directly through those switches, and bad contacts will disrupt the audio. When you say the “lower octave works”, I’m presuming you mean that the octave switch functions in down mode but not up mode. If that’s the case, I would also check both the physical operation of the switch and the line that feeds it. The switch flips a voltage onto a set of CMOS dividers, so if they’re not fed properly they won’t switch octave. The schematics are all on the site, so follow those and see how it goes.

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