WARNING: DO NOT attempt this if you are unfamiliar with soldering & dealing with power & circuits in general. ALWAYS wear SAFETY GLASSES when doing any soldering or working with any tools for that matter. Never leave the power adapters of these old systems plugged in. I'm not responsible for any harm you might do to yourself, others, or house by attempting this modification.
Step 1: Proprietary SNES Plug Be Gone for Good.
I purchased an old SNES from a facebook friend knowing that it didn't power on but soon as I received it I saw that the power post at back of console was broken off. I've always hated that design because it limits the options on power adapters to such a degree that it's borderline silly. Now with this one I had to figure out a way to get power to the console & using the original style adapter was out of the question now.
Step 2: Old Answering Machine Power Connector.
Finding a power input plug for the snes console was not too difficult. I was going to rob one from an old NES parts board but instead I found an old answering machine & just ended up using it since it was the proper size and sega genesis power adapter is perfect fit. Also the genesis power adapter polarity is the same with the outer metal part of the plug the positive and inner pin negative which is kind of unusual with power adapters.
Step 3: Desoldering the Old Power Input From SNES Board.
I used a soldering iron and desoldering pump to remove the old power input jack from the SNES motherboard (and the answering machine board of course) & it wasn't much fun. The plastic piece that the input connection spots on the back of the snes is held in place by the power jack so I had to remove all the solder as possibly then heat & pry a little with a straight edge screwdriver stuck under the edge. Little by little it came out until the point where I could slip it off the board.
Step 4: Answering Machine Jack Soldered in Place & Round Hole Made Square.
The answering machine jack had 3 solder spots but I only needed 2 which luckily lined up great with the board of the snes. The other simply hung off the side of the SNES board which originally shared same solder spot so it wasn't needed. Whatever jack you use be sure to check the polarity of the jack because just because this one matched with the one I removed from snes does not mean all will be the same. Check and double check this because get polarity wrong & you will probably fry your precious snes.
Once I had the new jack solder in place good I had to make the plastic piece fit back in place at the back of the snes. I used cutters, pliers, and a exacto knife to remove all the plastic preventing the square plug from fitting. This took a little time because I did not want to remove too much so it was a lot of test fitting to get the hole at the back the right size square. I was pleased with how it turned out & now it has a sturdy post much better than the sucky proprietary one nintendo used.
Step 5: Testing It Out.
After getting everything buttoned back up it was time to test it. I had no idea if the console would work or not. I had thoroughly cleaned it all & fingers crossed that the broken power jack was the only issue. Thank goodness success & it's so nice being able to use genesis power supplies as well as a host of others with the common post as long as they are 10 Volts DC & minimum 850 milliamps. Polarity has to be outer metal ring positive inner pin negative just always remember that. As I said the amps of the power supply can be higher than .85 amps (or 850 milliamps depending on how it written) don't go below that but for example a 1 amp 1.2 amp etc...will be fine but lower will overwork the power adapter making it get hot & burning it out fast or making your system glitchy. 9 volts probably be fine as well just be sure it's output is DC and DO NOT USE NES POWER ADAPTER because they output AC which will fry your snes and most other things. the NES had a AC to DC converting design inside the console & not sure why nintendo went that route.