It might come as no surprise that I like toasters. One of our more popular article is on the sunbeam toaster that’s automatic beyond belief! I saw some online videos about the To-ST1-T (Toasty!) toaster from Japan and purchased one. It really does produce perfect toast, including topped toast and the like. Sorted Food reviewed this toaster in 2022, initially making fun of he high price they came around when they saw the results. If you like thick “honey toast” style Asian toasts. This is the toaster for you. If you’d rather watch a video about the repair, it’s up on YouTube here: To-St1-T Toaster repair from 230 Volts.
The “incident”
It was late, and I was in a lack-of-toast induced brain fog. I placed my toaster down and plugged it into the transformer but mistakenly plugged it into the 240V output instead of the 100V output. The toaster let out a loud “pop” and also blew the circuit breaker the transformer was attached to. Plugging it into the proper voltage now revealed only a dead toaster. My heart fell, was my precious toaster dead for ever?
Investigating the failure
Many Japanese electronics of value are still made to be taken apart, and that’s the case for the T0-ST1-T. Six phillips head screws and the bottom is off, inside there is a metal cover with a bunch of wires coming out of it, which is held on by an additional two screws. Removing these and it was clear from the smell that somewhere in here was were the magic smoke had come out. It only took a few seconds to locate the blown out part, labeled “VSR1” on the board. With a 2A fuse right above it and a 20A fuse along the edge by the AC input.
So it’s obvious to a casual observer that VSR1 is shot, but what is VSR1? It’s a variable resistor. Specifically one that changes resistance in relationship to voltage. This is one that has a very high resistance until about 140V AC (RMS). Above that the resistance starts to head to zero. Why would you want that? Specifically to ensure that the 2A fuse right above it blows in an overvoltage situation. As the voltage went towards 230V AC (RMS), this varistor threw itself in front of the virtual bullet and went to dead short (or close to) to blow the fuse. Sacrificing itself to ensure the rest of the unit would survive.
Now here I have to give a shout out to the Mitsubishi engineers. This part is designed to fail in a very unusual situation (No one in Japan could plug this into 240V, as they run on a 100V mains, although there are 200V outlets these are very different and would be similar to an American accidentally plugging something into an electric range or dryer outlet). So these parts of the circuit are ONLY to make this toaster repairable in the case of a bad surge from the power company, or a gaijin(foreigner) plugging it into a very wrong power outlet. I really appreciate that the engineers thought this out, and provided this protection that could be repaired for about US$2 of parts and a few minutes with a soldering iron.
Parts needed
Obviously we need a new VSR1, which thanks to this post on Electro-tech online I know is a Panasonic V7221U varistor. This part was available from Ebay, but looked a bit sketchy. The exact part wasn’t on Digikey, but the VARISTOR 220V 1.75KA DISC 8.5MM (part ERZ-V07D221) seemed to hit the exact specs. at 21 Euro cents each, I got two.
But wait, earlier I said that the purpose of this varistor was to short out mains power to blow the fuse, so of course we also need the now blown 2A fuse. This kind of part is common and I got this one: FUSE BOARD MNT 2A 250VAC RADIAL . It was one euro each in summer 2025 so I agian got 2.
Why 2? Because the shipping is more than the part and I figure a spare is useful in case this happens again, or if I mess up the install in one way or another.
The Repair
The board was quite easy to open up and work on. Six screws to open the bottom of the toaster, 2 to remove a metal heat shield, and two more to remove the board itself. Total time to disassemble: 3 minutes (including photos).
So the two devices we want to change are the FUSE2 and the VSR1 device. Wouldn’t you know the friendly makers have included essentially a schematic on the board. This device was made to be repaired which is an amazing site in 2025, Even in our old retro electronics the schematic was normally pasted somewhere in a corner.
What is a Varistor?
This is a variable resistor, not to be confused with a potentiometer, which is also a variable resistor but different. This kind of varistor is essentially two diodes pointed at each other. In normal circumstances no AC current will flow between then as one of the diodes will block the flow. However diodes have a breakdown voltage, at which point the rapidly head towards a dead short (no more diode action). You can buy parts with a large range of breakdown voltage points, this one was 140 volts. That means that over 140V it will quickly go to dead short, which will blow the 2A fuse quickly and without endangering the components down stream. As 240V was much more than design, this happened explosively. I don’t recommend testing it!
Both the fuse and the varistor are orientation independent, so you can put them either way. As these are thru-hole components I de-soldered the old parts and put in the new ones. If you need help with soldering, there are lots of great videos on YouTube, search for “thru hole component soldering tutorials” and they will get you on your way.
Once the parts were on, it was time to give it a power up, on the right voltage this time of course!
Conclusion
If you have accidentally plugged you “fanciest toaster in the world” into 220-250 Volts mains outside of Japan and North America, there is a good chance that robust circuit design means you are out a few dollars in parts and shipping, and not out a 300 Euro Toaster. Please watch the video for the walk thru, and comment below with questions or if you’ve done this repair yourself!