The replacement capacitor in position 5 (my designation) is displaying the same symptoms as the one it replaced. I'm suspecting something else may be wrong inside the supply.
my diagram of capacitor polarities and backplane power wiring, which lists the polarities of the large capacitors incorrectly. I don't know how I made that mistake, but at least I did it consistently! :P
example of damage caused by electrolyte leakage. incidentally, this must have been from an earlier capacitor that was replaced, because the one I removed from this position was absolutely flawless.