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Not sure if this should go here or in Super User, but I'm primarily concerned with how safely I can solder an AC power connection with little/no experience.

So what exactly am I doing and why? I am looking to make some minor modifications to a home-theatre PC, one of which is relocating the power supply to inside the chassis. In doing so I would like to create a false PSU "plate" that I can screw into the back of the chassis to make it look as stock as possible and maintain an external AC power connection.

I've already cut out the back of a cheap power supply and all I need to do now is cut an AC power cable and solder it to the female plug so I can connect that to the power supply inside my chassis. But are there wattage/safety limitations with different types of solder? Are their certain types of solder that are better than others for handling AC current or just power in general? I have not purchased a soldering iron/gun or solder or anything yet, so if one thing works better than something else I'd rather know before I spend my money.

I'm not worried about how good/bad the actual soldering work looks once I'm done since it will be inside the case, but should I "finish" it in some way to make it safer/insulated? Like wrap it in electrical tape? Or if that's a stupid idea, heat-shrink tubing or glue or something else?

Any insight/suggestions would be appreciated!

EDIT: One of my concerns is that I would like to be able to draw a few hundred watts over this connection in case a turn this into a little living-room gaming rig in the near future. Not sure if/how that would affect anything.

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3 Answers 3

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Are you going to have the AC jack (power entry module) on your new back plate? If so, what kind of terminals does it have on the inner side? A photo or a pencil sketch of your new back plate could help us visualize the problem.

Without knowing anything else, I would recommend splicing the wires with a crimped butt terminal (like this one or this one). It's a thin-wall metal tube inside of an insulating plastic tube. Each end of the tube can be crimped onto a wire. Here in the US, you can get them in any hardware store. Crimped connections are less brittle, compared to soldering.

Splicing plus soldering works too. Heat shrink is a more reliable insulation than tape.

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    \$\begingroup\$ That crimping option looks interesting, but the inner terminals on the AC jack might be the wrong size/shape for that, I'm really not sure. I'll be home shortly and could upload a photo, but basically there are 3 prongs in a triangular configuration that were soldered to wires leading to the PCB of the power supply. I trimmed the wires off completely (perhaps not the smartest move) and only some bulbous solder remains. I assume I will need to desolder those terminals before I could do much of anything with them. \$\endgroup\$
    – Soldering Newbie
    Jan 12, 2012 at 23:00
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    \$\begingroup\$ @SolderingNewbie If you will be soldering/desoldering the terminals on the back of the AC jack, be careful not to melt plastic. A jack like that is usually made of ABS plastic, which has a low melting point. If the metal terminals are molded into the plastic, and you overheat them while soldering, they can become lose. On the other hand, since you are making your own panel, you can use any AC jack that you can buy. \$\endgroup\$
    – Nick Alexeev
    Jan 12, 2012 at 23:17
  • \$\begingroup\$ Some link rot here! But I get the point. \$\endgroup\$
    – nabulator
    Mar 28, 2020 at 21:01
  • \$\begingroup\$ @NickAlexeev The links you provided here died. Do you mind updating? \$\endgroup\$
    – Max
    Nov 5, 2021 at 13:41
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It should not be a problem soldering that.

I think that heat-shrink tubing is the right way, maybe with glue on the board but i suggest avoiding glue if you want to be able to do some maintenance.

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  • \$\begingroup\$ I would actually like to be able to draw around 300W or so. I'm toying with the idea of sticking a Radeon 6850 into the mix for some light gaming. I guess I'm worried whether a sloppy soldering job could handle that task. Would a poorly soldered connection offer too much resistance for several hundred watts of AC? \$\endgroup\$
    – Soldering Newbie
    Jan 12, 2012 at 22:48
  • \$\begingroup\$ Obviously it depends that what means 'sloppy' or 'poorly': as long as you can assure the right conductivity using the right amount of stain, it's not going to dissipate power, so it's not going to heat up and all should be working properly. Plus, if you isolate it properly (maybe a little more :D ) at least you lose the power supply but without generating a short. \$\endgroup\$
    – clabacchio
    Jan 12, 2012 at 22:51
  • \$\begingroup\$ You're starting to lose me. What is a "stain" in soldering terms? \$\endgroup\$
    – Soldering Newbie
    Jan 12, 2012 at 23:03
  • \$\begingroup\$ Sorry i was meaning the soldering paste, and i think that i mistranslated :D \$\endgroup\$
    – clabacchio
    Jan 12, 2012 at 23:11
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My understanding is you never solder an AC cable, a failure of the end device drawing too much current can melt and arc the solder

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