The "overmentioned fixes" are the only solution. Electrolyte Capacitors degrade over time: that's just basic chemistry. Leakage is not always obvious, they can also dry out or don't leak at all while they are bad. You need an ESR meter for testing capacitors.
Since your performa 475 is at least 16 years old, it's likely failing capacitors that cause the problem.
You may not like my answer but these "standard" fixes do solve the problem in 90% of cases like yours.
I have rebuild my IIsi PSU a while ago, it's 3 years older than your performa 475, but the PSU was a mess inside with many leaking capacitors.
Also you are looking at the logic board: the problem is most likely the power supply.
If you don't want to go this way and spend money to keep your computers in working condition then I would suggest looking for another hobby...
Sorry,
Nico