Synth Repair and Restoration Videos

One of the things I am really passionate about is saving old analogue synthesizers. In fact it's probably my most rewarding hobby. I spend hours and hours not just repairing synths but restoring them to "as new" condition. This can involve total disassembly and cleaning each part individually or searching the world to find an original replacement knob. Sometimes it takes much longer to clean a synth than it takes to repair it.

Another thing I am really passionate about is the transfer of knowledge. We are only the temporary guardians of these wonderful synths. It is our responsibility to pass them on in the best condition that we can. For this reason we all must share in the knowledge of how to keep them running and in good condition. We all must be aware of each synths strengths and common failure points. During each restoration I usually encounter a problem I have not seen before, or a mistake in the manual, or a better way to do something. Every piece of knowledge that I gain I will pass on through these video's.

My Youtube channel is www.youtube.com/c/GOLTSYNTH

If you are interested in synth repair, analogue circuit design, or electronics in general, please subscribe to my YouTube channel. I have not activated the monetary side of the account so there should be no ads. I plan to set up a Patreon account soon.

You can click the title of each video to open it at full scale in a new tab.

YAMAHA

YAMAHA CS-60

All three synths from the early Yamaha CS series are very highly regarded; for their expressiveness and their characteristic "Vangelis" sound. But with careful programming they are much more than that. The CS-60 sits in the middle of the early CS range and is an excellent acquisition if you can fine one. These video's show a full restoration including repair, cleaning and calibration. Including an explanation of the power supply and voicing circuits.

Full service guide for the Yamaha CS-60. How to calibrate the power supply and replace all electrolytic capacitors.

How the velocity/aftertouch works in a Yamaha CS-60 and how to clean and calibrate the synthesizer.

I explain the voice architecture, install LED's on the voice cards, and explain how the VCO's work. Then I show how to tune and calibrate the voice cards.


YAMAHA CS-20m & CS-40m

The third (and last) group of synths in the Yamaha CS series had wood side panels and rudimentary patch memory (the M in the name stands for Memory). However, in this late CS series only CS-20M and CS-40M had two oscillators per voice. The CS-70M had a single oscillator per voice, but contained two voice layers (much like the CS-80). These late CS instruments have the best filter sound of all analogue Yamaha's in my opinion, but unfortunately only one filter per voice layer. There are more video's to come on these synths, I just haven't got around to filming them yet.

I do an overview of the both CS20m & CS40m and compare the two. Then this video mostly deals with the CS20m repair. It was totally dead, with CPU problems, CV problems, analogue voice issues, the works. There was a lot to do!


ROLAND

ROLAND Juno 6

The DCO synth that started it all! (well sort of... it at least kicked off the Juno family and DCO use in general). This is actually a really charming synth. The lack of patch memory has huge benefit, it's the only Juno that does not have digital stepping in the filter. At high resonance the filter sweep is silky smooth. It's still super limited, but so are all the Juno's in one way or another.

In this video I go through some troubleshooting and a MIDI kit installation (from CHD). Voice 6 had gate issues and a dead VCA, while Voices 1 & 2 had no sub oscillator.


ROLAND SH-101

A great little monosynth (I mean "little" in vintage terms). I've never been a huge fan of the CEM3340 saw wave, but no one cares here as the pulse and square on this thing are awesome. Especially with the sub oscillator being able to go down two octaves. The filter is classic late Roland, very wet and powerful. The keyboard has serval weaknesses, one of which is shown in this video. The rubber key contact rubs directly on circuit board traces and can wear out tracks. Apart from that it's a relativity reliable synth with a simple design.

A full tear down and clean of the SH-101. Includes how to fix a common dead key issue and explains the 8 x 4 keybed matrix.


ROLAND TR-808

This is the one. The synth I can't be without. Many years ago I sold one only to buy it back again after all the Roland clones (of their own stuff, roll eyes) came out. In my opinion the 909 sound has been really well cloned for a while now, but there's something about an original 808 that is so much more organic than the clones. This is the only physical object that I have an unreasonable personal attachment to. I also know it's circuits like the back of my hand because I used to modify them in the late 90's.

The first video in my TR-808 Restoration series. Covers step switches, Start and Tap switches, switch caps, pots, knobs, screws and everything else that can be replaced using aftermarket parts.

This video covers the power supply, transformers, electrical saftey test, supply board voltages and related things.


MOOG

MOOG MEMORYMOOG

Probably the most notorious synth in the world of synth repair. The inside looks like spaghetti. But aside from the internal mess, it's really no different from any other analogue synth of the same era. The oscillators were common CEM3340's, the filters had been around for 15 years or so, even the VCA's were off-the-shelf. As far as problems go, they were all common too; connector issues, heat issues, tuning issues... nothing we haven't seen before. So I think the fear around this synth is misplaced. I will have a lot to say in this set of video's, which will be a comprehensive service and restoration guide.

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First Part
Comming Soon!

I will do a complete overview of the memorymoog including all common issues and then show how to fully restore it. This will include how to make it very reliable.


MOOG PRODIGY

The mini version of the minimoog. Basically the same ciruits, and the closest to the mini in sound. Basically the third oscillator became a permanent LFO (reduced cost) and the mixer section was reduced (no noise, less options). But what you get in return is probably the best oscillator sync ever heard. Amazing. In this set of video's I show a full a restoration.

I've skipped showing the first video on this page because it wasn't very good (it was my first ever video). This is the second video showing the restoration of my 1979 Moog Prodigy. I show how to disassemble and clean the potentiometers (pots).

Slightly controversal, but in small monosynths you can replace all the caps. Although, the electrolytics are the only ones that actually need to be replaced. It's up to you.

How to clean the top panel of the Moog Prodigy, how to re-stain the wood side panels and how to clean the keyboard, modulation wheels and knobs. It is the forth video in my Moog Prodigy restoration series.

How to calibrate the Moog Prodigy, including the temperature adjustment of the VCO's. I also explain how to troubleshoot faults in the VCO heater circuit.


AKAI

AKAI AX-60

So many things about this synth remind me of the Memorymoog, and it's not just that they share the same Panasonic keybed, or that both can make the VCO modulate the filter. Their standard electronics are not very reliable and both have power supply issues. So much so that I decided to redesign the power supply in both synths, but it's the AX-60 that benefits from it the most.

If you have the standard power supply please don't adjust it as I do at the end of the first video. Yes the voice chips will tune better (and that was my point) but the standard power supply has a lot of trouble holding that voltage for a long time (and may die). If your CEM93394's have drifted permanently, it's best to just upgrade the power supply. The synth tunes MUCH better after that and sounds a lot better. I will place the board files on this page once I have tested the next version, so you can build the power supply yourself (or get someone experienced with electronics to do it for you).

How to repair dead voices and fix autotune problems in the Akai AX-60. I also explain how the control volages are applied to the CEM3394 synth voice IC's.

How to install LED sliders in the Akai AX60. I also show how to clean the panel and replace the switches.

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Third Part
Comming Soon!

I have redesigned the power supply to allow it to be adjusted correctly. It was a great success and the synth tunes and sounds much better now. I will complete the video as soon as I can.


ARP

ARP AXXE

The 4072/4075 is my favourite 24dB low pass filter of all time. I think I like the 4075 better, but both are great. Even though at first glance the schematics for both filters look the same, they are actually quite different, especially in the feedback loop (the resonance) and the biasing. The ARP oscillator also is also quite remarkable, it sounds absolutely massive and tracks over nine octaves. Quite a remarkable feat. These video's show the restoration of the ARP Axxe and how to install LED sliders.

The first video in my ARP AXXE restoration series. I replace the power supply and rebuild the 4075 filter board.

How to repair the ARP AXXE main power ON-OFF switch.

How to troubleshoot the Sample and Hold, Portamento and CV Memory circuits in the ARP Axxe. Including an explanation of how the circuits work.

How to install LED sliders in the ARP AXXE synthesizer.


KAWAI

KAWAI SX-240

The split/layer capability of the SX-240 is really great. It really fattens up the synth and helps the DCO's come to life. I've never been a huge fan of the filter but the ensemble (chorus) effect on this synth is massive. This synth does much better strings than the Juno's in my opinion. The first video explains how the DCO's work and the second fixes a battery leak.

I explain the SX-240 DCO. In fact I explain nearly all DCO's in vintage synths, and my thoughts on what Behringer might do on the Deep Mind 12.

I explain the chemistry of battery leaks and how clean up and repair the PCB.