If it’s a pretty old amp (which it is), there’s a good chance some of the capacitors in the power circuit (and likely everywhere inside) have gone bad. This will cause it to not turn on, and in some cases draw too much power.
What you can do is open it, and then desolder all of the capacitors (making a table to note where they go based on their values, (eg. C16 might be 470uF 35V) and then go on somewhere like Digikey or Mouser and find the capacitors you need with their part search tool.
Once you replace them the problem should be fixed! Also, absolutely make sure to put the capacitors in the board with the correct polarity. Not doing this will make them explode.
Additionally, you should only have to replace capacitors that are of the aluminum electrolytic variety, so any ceramic ones can stay, etc…
I would recommend getting capacitors from Würth or Nichicon, but if you have to get them from other manufacturers due to stock shortages, that’s okay.