I've noticed the same green goo on other 1A2 systems, usually on or under the power supply with no other apparent sources. It's a thick liquid, probably from a capacitor. I wouldn't eat it, but it's nothing to worry about in a non-functioning system.

It looks like your power supply is directly over the goo, so that's probably the source.

Joe
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No trees were harmed as a result of this posting; however, many electrons were severely inconvenienced.