I suppose you can open it up (if you have the right nut driver thing, same as N64 and GC) and see if a solder joint broke loose. If you know how to solder you might be able to fix it. If you want to get a whole new replacement jack, it's somewhat complicated, as the different localizations use different plugs, jacks, voltages (not just changes in voltage, but AC vs. DC) and currents. Read this post here for some clarification. It seems the US SNES has a proprietary plug and jack, so good luck finding an exact replacement if you have that. If you're not afraid of modifying your case and power supply, you can get a different sized jack and plug, as long as the center is negative if you have DC.
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