The 100V question, and the fourth door (Mercari) — follow-up to the Hard Off / Digimart / Yahoo Auctions threads

[RenSynthJp]

Three threads back I walked through the three ways to find Japanese gear: the Hard Off junk corner, Digimart shop stock, and Yahoo! Auctions private sellers. The same reply kept coming back in one form or another, and I dodged it every time because I did not have a good answer yet: what do you actually plug it into once it lands? Here is what I have since worked out, plus the one sourcing door I left out.

The power situation, plainly

Japan runs on 100V, which is lower than anywhere else. Domestic-market gear is built for it, and a lot of vintage Japanese gear is hard-wired for it — no voltage selector on the back, no universal switching supply, just a transformer wound for 100V. That splits into three cases:

- Modern gear with a universal supply (roughly "100-240V" printed on the brick or the rear panel). Plug adapter and done. Most current Roland/Korg/Yamaha products are here.
- Modern gear with a Japan-only wall wart. The unit is fine, the supply is not. Replace the supply with a correctly specced one for your country and check polarity — centre-negative is common on Japanese pedals and getting it wrong is expensive.
- Vintage gear with an internal 100V transformer. This is the JX/MKS/M1R/TX rack generation, the Boss and Maxon pedals with the old supplies, most 80s Japanese-market keyboards. It will physically run on 120V and it will sound fine, but you are running it around 20% over spec, which shortens the life of the filter caps and cooks the regulator. On 230V it just dies. This is the case where you buy a step-down transformer, sized with real headroom, not the 30W travel brick from the airport shop.

The 50/60Hz thing gets brought up a lot and matters much less than people think for anything with a switching or regulated supply. It does matter for gear with a synchronous motor — tape echoes, some drum machines, turntables — where the motor speed is tied to line frequency. Worth knowing: Japan itself is split, 50Hz in the east including Tokyo and 60Hz in the west including Osaka, so "it worked in Japan" does not even tell you which frequency it was working on.

What to ask the seller before you commit

The listing photos almost always include the rear panel. If they do not, ask for one, because the voltage rating is printed there and it settles the whole question in one photo. For anything with a wall wart, ask for a photo of the label on the wart too — the pedal being 9V DC does not tell you what the Japanese supply actually delivers.

The fourth door

Mercari Japan is the one I left out of the earlier threads, and for pedals and small boxes it is often the cheapest of the four. It is a phone-first flea-market app rather than an auction site: fixed prices, individual sellers, enormous turnover, and listings that vanish within hours because there is no bidding clock to wait out. The vocabulary is the same as the Hard Off thread — 動作確認済 tested, 完動品 fully working, 通電のみ確認 powers on only, ジャンク as-is. The service fee on that side is a flat 300 yen an item, which I re-checked on live item pages this week, and being flat rather than a percentage is exactly why it suits cheap pedals badly on their own and well in batches.

Same structural blocker as the other three doors: a Japanese account, address and payment method, no international shipping. So it is a proxy either way.

I wrote the Mercari side up in full — what blocks the checkout, the condition vocabulary, the fee arithmetic — here: Mercari Japan explained: buying from mercari.jp from overseas

And this is the live search I keep open when I want a price sanity check on synth gear currently listed in Japan: synthesizers listed in Japan right now. Disclosure, same as the previous three threads: that second link is the proxy service I use, so treat it as a price reference rather than a recommendation.

The thing I still cannot get a straight answer on: for a hard-wired 100V vintage rack unit, does anyone here just rewind or swap the primary rather than living with a step-down box under the desk? Every tech I have asked gives a different answer about whether it is worth the labour.