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I bought another soldering iron, very expensive to me. I am very exciting about it. Upon receiving it, My heart is broken. First, I saw the label, 220V; Our AC voltage is 110V. Tried it, doesn't work. Not even heating up.

With a heavy heart, I disassembled it, trying to fix it. Great news, the heating element is measured 62 ohm, so It should work with 110v. I have tried to change 40K to 20K, and 1K to 500, but it doesn't work.

Here is the schematic that I got from tracing the PCB. There is a MCU supposedly used to controlling the duration of the triacs, thus giving it a variable temperature. Also, it's a 120W soldering iron. For me, I can live with fixed power @ 60W. what should I do here? I am not very familiar with AC circuit.

  • 1
    \$\begingroup\$ The capacitor you have marked 250V may be the problem- too small value for 110V. \$\endgroup\$ Apr 25, 2016 at 3:44
  • \$\begingroup\$ 154J=150nF? that's the label on the cap. \$\endgroup\$
    – user83582
    Apr 25, 2016 at 3:50
  • 2
    \$\begingroup\$ A good idea may be to find a schematic of the same model as a 110VAC version, (if it exists). Then you may be able to do a correct part for part conversion. Don't just assume every part value needs to be halved. Important: Do note that the whole circuit is working directly from the hot mains, so be extremely careful if you do any live testing or probing. \$\endgroup\$
    – Nedd
    Apr 25, 2016 at 5:31
  • 5
    \$\begingroup\$ I think you should return the iron to the seller and get on that is correctly designed for your locale's rated voltage. \$\endgroup\$
    – uint128_t
    Apr 25, 2016 at 5:54
  • \$\begingroup\$ At half the supply voltage you'd get 1/4 the power, so a 120W heater would give 30W not 60W. Toss a coin between replacing teh iron and buying a transformer. \$\endgroup\$ Apr 25, 2016 at 10:29

2 Answers 2


Rather than do all that engineering and risk damaging the soldering iron, for such a small load (120W) I'd suggest just getting a commercially available 120V to 240V transformer or adapter in the 200W capacity range. They're not expensive.

Also, there's a provision for installing 220/240V outlets in North America. It uses these outlets made for 240V which install exactly the same as common 120V outlets, except keyed different. It's called NEMA 6-15. 240V breaker and you're done.


You bought the wrong model, or were sold or shipped the wrong model. The obvious answer is to fix this basic mistake. Return the iron to the seller and exchange it for the 110 V model. You may have to pay a restocking charge if you ordered the wrong model in the first place. If not, this is really the seller's obligation to fix.

This is a purchasing problem, not a electronics problem.

  • \$\begingroup\$ The OP formulated this as an adaptation problem, so not this is an electronics problem. He has already started working and stuck where he is now. \$\endgroup\$
    – sharptooth
    Apr 25, 2016 at 11:50

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