The desktop in the workshop had started refusing to boot from cold. Hit the button, fans twitch a quarter turn, nothing. Wait ten minutes, try again, and it springs up like nothing happened. Classic symptom, and you can usually call it before you've got the lid off: it's the PSU, and it's the capacitors.
Opened it up and there they were, two of the bulk caps on the secondary side with domed tops, one of them weeping a little crust of electrolyte. These are the bargain-basement capacitors that get fitted to save a few pennies per unit and then fail four years later, right on cue, just outside any warranty that ever existed.
I had a couple of decent 105°C-rated Rubycons in the parts drawer at the right value and voltage, so it was a ten-minute job. Discharge the big primary cap first, because that one will absolutely ruin your afternoon if you get casual with it. Desolder the two swollen ones, note the polarity before you do, fit the replacements the right way round, reflow, done.
Powered up first time and cold-boots cleanly now. Total cost was about two quid in parts and a coffee's worth of bench time. The replacement supply I'd half-talked myself into buying was forty. I know which one feels better, and it isn't the new box in the cupboard I no longer need.