There are timing relays for under $50 that can delay the power to the amps for a few seconds. You just need to buy a 230V model (for input and switch) that has the current capacity for your sound system.

If you’re looking for a fault and can’t see it, it’s sometimes possible to sniff it out. Components can be burned out, but the damage is barely visible, if at all. It could be a tiny crack in the packaging. It will often smell like burnt plastic for a long time. Locate the rough area and concentrate on these parts.