Since I didn’t find Tatung spares easily, I decided to do what every engineer would do: check with someone who knows such stuff. Luckily there is a power supply developer sitting next to me, who pointed out that the damage might be contained to the AC part only (If one is lucky, and if the power supply design was good).
Turns out he was right. After googling a lot, I now understand a bit better what happened. I’ll share hoping it helps some other silly furinners or locals that plugged in 110V appliances into 220V outlets.
The thing that blew is a varistor, also known as MOV (Metal Oxide Varistor). And it worked exactly as designed, luckily. This thing is supposed to help against spikes of too high voltage. It does so by shorting the two AC input pins whenever the voltage is too high. Normally such voltage spikes happen only for super short times, which the MOV can withstand without getting too hot (they still wear out after a few such events, though). Now since silly me supplied 220V, and this MOV apparently was a type that trips below this voltage, all that happened was that the MOV shorted the input pins, causing the input current to be abnormally high, which in turn caused the two small fuses in the power supply to trip. After that, no more current flowing. In that process the MOV sadly died, but the rest of the power supply was most likely unharmed.
A quick trip to the underground Guanghua Electronic Plaza (near the computer shops above ground) later, I had the necessary 2 replacement fuses and a suitable MOV. The choice of MOVs >110V and <220V there was very limited, so I went for the only one I could find, a 140V United ChemiCon TNR15G221K:
For the fuses, I went with the same rating as the originals had (220V/5A/slow), only in a round housing vs. the original square ones:
The only other component in the AC side is a 1M Ohm discharge resistor, which despite being blackened by the MOV soot turned out to be still OK.
After de-soldering, cleaning, and soldering of the replacement components the power supply still looks like shit, but works
- It’s best not to plug 110V devices into 220V sockets
- Don’t mess with AC if you don’t know how to do so safely
- You could also just leave out the MOV, it would still work. For testing this is fine, but your device is then unprotected from surges (or 220V wielding idiots like me).