Hard solder

[MadMan]

Possible the PCB pads that the electrolytics were soldered to are just too big and have too big a thermal mass? Clean your solder tips, especially where they connect to the iron for good thermal conductivity. Or electrical conductivity for a solder gun. Can't tell you how many times I get frustrated with an iron or gun that seems smoking hot, but just isn't enough to melt anything.

Also remember modern solder is lead free and has a higher melting temp. For all we know, they used something even tougher to hold the larger components, like electrolytics. Could be like nickel based solder. No idea why though. I mean, it would make some sense to have more mechanical holding power for large components, but seems like an unnecessary extra expense of material and labor for what's still sort of a run-of-the-mill PCB.