The Roland SH-3A is an analog monophonic synthesizer released in 1974 by Roland. Known for its warm, rich analog sound, it was an early synthesizer that offered unique flexibility with its multiple waveforms and subtractive synthesis capabilities. It features a single oscillator with selectable waveform options, a resonant low-pass filter, an ADSR envelope, and a noise generator, making it ideal for creating diverse basslines, leads, and sound effects.
A standout feature of the SH-3A is its oscillator mixer section, which allows users to blend various waveforms for complex tones, an uncommon feature in synths of its era. The SH-3A also has a built-in LFO for modulating pitch and filter effects, which, alongside its straightforward layout, makes it accessible for both beginners and experienced synth players. Its rich, thick sounds and unique tonal characteristics have made it a cult favorite among electronic musicians and collectors.
Many years ago, I acquired a vintage SH3a synthesizer from Japan, thanks to a friend who managed to secure it for me. It was fully functional at the time but definitely far from pristine. Between life’s priorities and other projects, I kept delaying the restoration, setting the SH3a aside until earlier this year.
Finally, I decided it was time to bring this synth back to its former glory. However, I quickly ran into a few challenges. The output volume was notably low—far below the levels specified in the service notes. No amount of tweaking could bring it to an acceptable range, so I knew this would require a deeper dive into the circuitry.
Additionally, the sliders had become incredibly scratchy over the years. Their values would jump erratically, and they were difficult to adjust smoothly. Every attempt to move a slider felt rough and unpredictable, which detracted from the playing experience. And to add to the restoration list, the rotary potentiometers had their own scratchiness issues, needing a careful touch to regain their original functionality.
Upon disassembling the unit, I immediately understood why I had delayed this project. The front panel assembly is notoriously complex to dismantle, and the internal wiring resembles a “wire bomb.” The wiring is densely packed, and as soon as the internal PCB is loosened, wires scatter, making it challenging to move components or perform visual inspections.
New transformer installed! I needed to replace the transformer because it was originally set up for Japan’s standard voltage. I installed a 230V version to safely use it in my region. This required careful handling and some adjustment to ensure physical compatibility.
Then I installed new capacitors in the PSU. One of the most critical parts of restoring any vintage electronics is ensuring a stable, reliable power supply. Given the SH3a’s age, the power supply unit (PSU) was long overdue for some maintenance. Old electrolytic capacitors in the PSU can lose their effectiveness over time, leading to voltage instability, noise, or even complete failure in some cases. I knew that recapping the PSU with fresh electrolytic capacitors would be a crucial step to bring this synth back to life.
Two synth boards were next to be recapped. I used high quality Panasonic and Nichicon capacitors to recap them. Electrolytic capacitors, while excellent at their job in filtering and stabilizing power, degrade with age. Over the years, the internal electrolyte can dry up or leak, which affects their performance and can put other components at risk.
Since all of the sliders were barely moving / stuck and completely scratchy they had to be restored. To get access to the sliders, the first step was to disconnect the sub-PCB. This required desoldering all the connecting wires carefully. Each wire needed to be removed to allow me to safely work on the sliders without damaging any nearby components. As tedious as this process was, it was essential to prevent any accidental stress or damage to the rest of the circuit while removing each slider. With the wires safely removed, I moved on to desoldering each individual slider from the sub-PCB. This was a delicate process, as the sliders in the SH3a are tightly integrated and soldered directly into the board. Using a desoldering pump and taking my time, I carefully released each slider from the board, making sure not to damage any of the delicate connections.
After that each slider is disassembled and cleaned. These sliders had decades of buildup and wear, causing them to feel sticky and rough. Dust, dirt, and oxidation had accumulated inside, leading to erratic jumps in value and unreliable performance. Simply cleaning them externally wouldn’t have been enough; a complete disassembly was necessary to restore them to a usable, smooth condition.
The reason sliders could barely move was because the shafts were dirty with the old grease that turned into some sort of resin that acted more like a glue. Looking at the tip of a Q-tip one can see the amount of dirt collected.
And the contact area was simply disgusting.
Once cleaned it looks like new.
Contact pins were dirty as well, just look at the Q-tip after the clean up. Pins are now like new.
In order for the slider to move smoothly a new grease is applied.
And more sliders! I’m ready to open each one up, clean out the debris, and re-lubricate them to get them sliding smoothly again. Once they’re refreshed and operating smoothly, I’ll resolder them back onto the PCB and reconnect the wires to the sub-PCB. This careful restoration process will help ensure each slider performs as it originally did, allowing for precise, smooth adjustments and reliable functionality.
As part of my ongoing restoration of the SH3a synthesizer, I decided to give some attention to the internal metal plate. Over years of use and storage, the plate had accumulated a bit of grime, dulling its original shine which can lead to potential corrosion in the future. Before applying any cleaner, I carefully applied WD-40 to a piece of cloth avoid getting WD-40 or any residue on sensitive internal components. I gave it a gentle wipe to remove any surface dust and dirt, which would make the WD-40 application more effective. Using a clean cloth, I applied a small amount of WD-40 and began wiping down the metal plate. WD-40 is great for more than just lubrication—it’s also fantastic at breaking down grime, loosening dirt, and adding a protective layer against future corrosion. I worked it into the surface, ensuring it reached every corner and groove, and let it sit briefly to allow the solution to penetrate stubborn spots.
Each rotary potentiometer was disassembled and cleaned, exact the same treatement as the faders.
Another board to desolder and we are almost done. The wires are complete mess and really discourage you to dig deeper, but you have to go until you reach the end. New capacitors can be seen installed on the synth board.
Knobs and caps are to be cleaned as well.
Front panel sliders and potentiometers are cleaned, the wires and soldered back in. Working with so much wires in such tiny space can be a bit unpleasant (to say it politely).
Before assembling it I also took time to wash the front panel just to make it fresh and clean.
With the restoration work on the SH3a’s synth section completed, it’s finally time to move on to calibration. This is where precision really comes into play—setting the synth’s various parameters to ensure it performs with the best possible stability and accuracy. Calibration involves adjusting a range of parameters across multiple circuits within the synth. Each setting has an impact on the sound’s pitch accuracy, waveform stability, and overall tonal characteristics. The process takes several hours if you want every parameter precise to the last decimal point (actually not necessary, but I do it anyway).
And we’re nearly there—almost finished. The SH-3a, as it turns out, lacks a classic CV/Gate interface, which led me to install an additional board. This board converts standard CV/Gate signals into the specific voltages the SH-3a requires (if you’re curious, look up “CV interface for SH-3a” for more details in web search). However, this setup presents a bit of a chicken-and-egg dilemma. To use the interface, you need to calibrate it, but accurate calibration demands a MIDI-to-CV interface that’s as close to perfect as possible. It’s a subtle challenge, but one worth solving to unlock this synth’s full potential. Anyway, here’s how I solved it.
I have three MIDI-to-CV interfaces at my disposal: the Waldorf Pulse+, Kenton PRO2, and Doepfer MCV1. Obsessed with precision, to ensure maximum accuracy, I conducted an in-depth analysis which took a good portion of the day, measuring each interface down to multiple decimal places. My goal was to identify the most precise reference interface for calibrating the new CV input on the SH-3a. Specifically, I examined the tracking precision and offset stability of each unit across a five-octave range. After careful analysis, the Kenton PRO2 emerged as the most consistent in tracking accuracy and offset calibration. I also tested the MIDI-to-CV response speed on all three units, and found them all to perform reliably with minimal latency, although this was not necessary for this task (it was more to satisfy my curiosity).
My SH-3a now has three additional ports on the back and can be run with any regular MIDI/CV interface. Calibration of the new CV/Gate interface of SH-3a can take about an hour, and you should make sure that both your MIDI/CV interface and SH-3 are warmed up before doing it. Also make sure to repeat the procedure again after an hour for the fine tuning and verification. With these steps, SH-3a will be primed for precision control through its CV/Gate interface.
And here we are one week later. The unit is completely restored. Thanks to new capacitors in the PSU and on the voice boards, the unit now tunes within a minute and stays in tune. The sound is phenomenal! I still remember it, as it was gathering dust at one point I thought of selling it. There is no way I would sell it now. There’s really nothing out there that sounds like it. We live in an age where anyone can download a VST synth and play it, but only a few have an actual synth from 1974!
