marantz amplifier PM-84

the output transistors are screwed to a big aluminum heatsink.
the transistor terminals are not soldered but simply push into sockets.
i was thinking of cleaning the terminals with some steel wool
then spraying the sockets with contact cleaner for a better
connection. is this a good idea? are there better alternatives?

the original problem was humming(a couple of high esr caps and some
dry joints)