PWM chip is safer than 2-transistor, but FUBAR crappy caps will ruin the day anyways.
The Antec SL300 in this post mortem had a UC3844B PWM controller on +5VSB, and yet:
"... With only the old 680µF Fuhjyyu caps, the 5VSB output settles around 5V, is horribly noisy and shows horrible power-up transients peaking at up to 16V (clearly no good for capacitors rated only for 10V) ..."
"... When all of the capacitors on a flyback power supply's outputs have failed, there is little left standing in the way of flyback operation generating high voltage spikes and destroying components ..."
elod wrote:I remember the caps blowing on the 5vsb line in these supplies right after the 2 year warranty ...
^ That's the kinf of hard earned wisdom that screams RECAP!!!.
For retrocomps with dubious caps onboard the PSU (aged or crappy) that are used only occasionally, I'd switch the PSU off whenever the comp is turned off. +5VSB circuit is always live whenever ATX PSU is plugged to wall and switched on (regardless of comp turned off), so +5VSB caps are always receiving juice, ripple and heat (with the added 'bonus' that PSU fan is stopped and moving no air). Switching off PSU whenever comp is turned off spares them a ton of stress.
If we also unplug PSU from wall whenever comp is turned off, we'll get full protection from storms (barring a bullseye direct lightning strike that sets our home on fire).