@JDW Good catch. I didn't think they would have different pitches. The pitch for the SE/30 looks to be 0.4" (~10mm). It may be difficult to find an exact replacement, so I think single sockets would be a good, easier to find alternative. Another advantage is if you want to fix just one broken socket, then you could clip the supports in between the two sockets and leave the other one alone.
On a 30 pin SIMM pin 1 and pin 30 are 5V DC and that square pin that shorted is pin 1 on the socket. Pin 2 is /CAS.
Burning plastic turns to carbon which is conductive so clean the black goo off with alcohol and see if it is still shorting the 5 volt rail. If all those tantalum capacitors were shorted to ground I expect them to explode so its something else. The power supply should shut down on a direct short.
Well, went and checked - C155 is shorted, along with just about every other capacitor. The +5v rail is shorted to ground somewhere; I'm guessing that probably fried a few things.
Oh well, it will make a nice shelf piece.
Plastic, which is what made the smoke/burning smell; there wasn't any visible metal anywhere nearby, which is what threw me for a loop. I just got back from running errands, so I'm going to eat dinner and have another look in a few.