A while back I think I may have plugged the wrong power adapter into my MIDI keyboard and it started to smoke and then never turned on again.
So… I popped it open and it looks like it's a burnt 1N5187 diode.
I come from the completely different world of stats and maths stack exchange so I'm not really qualified to speak on these things and I have little training in electrical engineering and hardware.
But I have taken a class in soldering and so I came here to learn from anyone willing to advise whether you would recommend for/against me getting a soldering iron to replace it if I bought the right part and isopropyl-ed the affected area with a q-tip (assuming I'm a beginner).
Also, I'd like to understand what role this diode plays in the circuit. Just by looking at it, does it seem like the burnt areas would inhibit the flow even if the diode was replaced.
Any commentary, links, or help from experts is greatly appreciated. Main goal here is to learn more about how these things work.
EDIT: Adding image of the the other side of the circuit board.
Best Answer
After further consideration, I've added my earlier comment as an answer. This is not an answer to the question that you asked, but it is an answer to the overall situation.
You commented on an answer:
That IC (U1?) seems to line-up with the melted area on the inside of the case, which confirms that it has been destroyed. So your problem is not actually about a burnt diode - instead you have at least one destroyed SMD IC (replacement needed) and possibly other destroyed components too. Replacing the diode alone will be a waste of time. Based on your comments, this repair is not within your skillset, and is off-topic here as a non-trivial repair of a consumer item, sorry :-(
I don't know the availability or cost of replacement parts for that specific device, in your specific part of the world (wherever that is :-) ). This is one reason why repair questions are off-topic - there is too much "question-specific" detail that won't help future readers :-(
Assuming all of the electronics is on that one PCB, then if you can get a replacement PCB, at a price you are prepared to pay, then (depending on the mechanics of actually replacing it) you might be able to exchange that on your own.
Perhaps you were thinking about replacing that SMD IC? Unfortunately, even if you could find a replacement for that damaged IC (and it may not be sold as a spare part anyway, if it is a custom or pre-programmed device) you then need to find someone with SMD soldering skills. And even then, that's assuming that only that IC (and the diode) have been damaged. Without a full evaluation of the whole keyboard, it's possible that even more components have been damaged, so that replacing even the diode and that SMD IC might not be enough! Sorry for the bad news, but I think it is important to be realistic. :-(