No or very low sound is typical for bad capacitors. The board has to be completely recapped.

It's a 22 year old Mac Portable so it's normal the capacitors need to be replaced.

Look for green dirt on the PCB near the small SMD radial capacitors.

It's also perfectly possible to you don't see any obvious leakage on the PCB, nevertheless an ESR tester will prove they are all faulty.

I recommand not the use the board anymore until you replace the capacitors as otherwise you can make it beyond repair.