I initially thought it was a weld, too, but it's THICK to be a weld! I forgot about JB Weld, though, and that's really the most likely guess.

The fact that it's not actually connected to anything is the weird part. I suspect that the previous homeowner had the same leak and just jammed a bunch of JB Weld up there until it stopped.

I feel like the proper solution would be to somehow get the panel off, then remove the trough and either fix the leak properly or replace it altogether. But I don't know how to get it off with those copper pipes in the way, I feel like it would require pumping down the system first so I could cut the pipes or something :-/

This is your luck day Jason. First and foremost non of the the regular blowhards showed up to babble about natl building code and bull crap. Before tearing into it,make sure the water isn't the result of clooged drain line. If you are certain there's damage needing repair, "CAREFULLY" cut the section of panel out that has pipes going through it. That will leave a piece of panel attached to pipes and coils but you will have unobstructed access to coils and condensate pan. My tool of choice would be a 4.5 angle grinder with cutting disk. If you don't own a grinder and don't have other use for one, something like a Dremel tool with cutting disks or even a drill motor can make the cuts with enough patience. Patching cuts can be done several different ways. Got it ? Then go get'um.

Condensation is external to the refrigerant conduits. You shouldn't need to pump down anything to seal the drain pan and pipe.

Sorry, I don't think what I meant came off properly.

I was thinking more about how to get the panel off, around the copper pipes, so that I could access the leak in the black connector. I'm guessing that those copper pipes carry freon, and I don't see a way to disconnect them anywhere.

@klem1, your post just now showed up! 24 hours late is better than never, I guess :-/ I DO have a Dremel, though, along with a stack of cutting disks, so I might really go that route. I kinda hate to, though, because I feel like there HAS to be an alternative... how would an HVAC tech get to it?

This ac tech always cut the panel to avoid pump down and recharge unless there was reason to remove coil. You might only need to cut a few inches making a notch from pipes to panel edge.

Would you mind saying how you visualize a simpler soultion,much less doing it any other way without specialized tools?

It isn't unusual my posts are delayed because keyboard jockeys flag them for review while they search online for answers they can plagiarize.