When we checked eBay US in October 2026, a search for Roland in the Synthesizers category showed more listings located in Japan than in the United States. Plenty of vintage synths are Japanese domestic units, more came from Europe or Australia, and each was built for its home country's power. Plug one into the wrong voltage and you're asking its power supply to run outside what it was designed for. Here's how to tell what you're buying, what the fixes are, and how to get a heavy synth to your door in one piece.
Who uses what voltage
- Japan: 100 volts. Eastern Japan, including Tokyo, runs at 50 Hz, and western Japan, including Osaka, runs at 60 Hz.
- United States and Canada: 120 volts at 60 Hz. Older American gear is often rated 115 or 117 volts, older figures for the same supply. Moog's Minimoog manual tells owners to plug into any conventional 117-volt outlet.
- UK, Europe and Australia: 230 volts at 50 Hz, often written 220 or 240 on older gear.
Japanese plugs fit most North American sockets without modification. That's convenient, and it's also the danger, because a 100-volt synth goes straight into a 120-volt wall with nothing to stop you.
What the wrong voltage does
A synth's power transformer steps the wall voltage down by a fixed ratio, so its outputs rise and fall with the input. Run a 100-volt unit on 120 volts and every supply rail starts out about 20 percent higher than designed, which pushes the regulators and capacitors harder than they were meant to work. Plug a 117-volt unit into 230 volts and the transformer puts out roughly double. If you're lucky, the fuse blows first.
Low voltage causes trouble too. Korg's Polysix manual warns that at 90 percent or less of the rated voltage, noise and stability suffer. A 117-volt synth run on Japan's 100 volts is below that line.
Frequency is a separate issue. A transformer changes voltage and leaves frequency alone, and equipment with internal transformers designed for 60 Hz can overheat at 50 Hz even on the right voltage. That matters most if you're taking an American synth to Europe.
Which models switch and which don't
Only some synths can be changed over with a switch. These are the ones we could confirm from the makers' own documents.
- Prophet-5: it has a line voltage selector. Sequential's manual says units shipped to the US and Japan were usually set to 115 volts and European ones to 230, and that the fuse has to change when you move the switch. Ask the seller for a photo of the switch and the fuse.
- Juno-106: Roland built regional versions. The service notes list separate power and fuse boards for 100/117-volt and 220/240-volt units, plus different AC inlets, so moving one between regions is a parts job for a tech.
- TB-303 and SH-101: both run on batteries or an external AC adapter. The TB-303 manual says to use the BOSS adapter that matches your country's voltage, so the fix is buying the right adapter.
- Minimoog: the US manual specifies 117 volts.
- Polysix: Korg's manual tells owners to always use the correct line voltage and to check a suspect outlet with a voltmeter first.
For anything else, don't guess. Read the plate on the back panel in the photos, and ask the seller whether the unit has ever been converted. If it has, ask who did the work.
Step-down and step-up transformers
A 100-volt Japanese synth can run in the US on a step-down transformer that turns 120 volts into 100. A 117-volt American synth in a 230-volt country needs a step-down from 230 to 117. A step-up does the reverse, for 230-volt gear on US power. Pick one rated comfortably above the synth's power draw, which is printed on the rating plate. For scale, Roland's service notes put the Juno-106 at 25 watts. Bigger synths draw more.
A permanent conversion inside the synth, done by a tech, saves you the box on the floor. On a Prophet-5 it's the selector switch and a new fuse. On a regional-version synth like the Juno-106 it means swapping parts, so get the tech's quote before you buy a foreign unit to convert.
Shipping a heavy synth
Old synths are heavy, and some are enormous. Sound On Sound put the CS-80 at 100 kg with its built-in case and said it really needs a full flight case to protect its voice circuitry. Yamaha's own manual says at least two people should lift it. Sound On Sound also called the Taurus pedals very heavy, and Sequential urged Prophet-5 owners who move theirs regularly to buy a road case.
Before you pay, ask the seller how they'll pack it. Here's what to look for.
- Double boxing: the synth in a box or case, inside a second, larger box. FedEx's packing guidance calls for 2 to 3 inches of cushioning on all six sides.
- Flight cases: an original or road case is good protection. Ask whether it ships inside an outer box or on its own, and whether the synth is padded inside it.
- Batteries out: Roland's SH-101 manual warns that batteries can break out of their housing in transit, and loose cells can leak. Ask for them to be removed.
- Any orientation: FedEx says it can't ensure "This End Up" markings are followed, so the packing has to protect the synth upside down too.
- Tape and signature: FedEx recommends tape at least 3 inches wide across every seam and suggests requiring a signature for valuable items.
- Freight: a CS-80, or anything too big for a parcel service, goes by freight. Ask whether the seller will crate or palletize it, and get the delivery terms in writing.
What to ask the seller
- What voltage is it, and can you photograph the rating plate?
- Has it ever been converted, and by whom?
- Does it come with a transformer or adapter, and what's printed on it?
- How will you pack it, and will you take the batteries out?
- Is there an original case, and will it ship inside a box?
On arrival
Photograph the box before you open it, and keep the packing until you've tested everything. If it arrives cold, let it reach room temperature before you switch it on. Read the rating plate again before the plug goes anywhere near the wall. For what to check once it's running, see what vintage synth service involves, and for listing warning signs, our eBay red flags guide.
