hifi engine

RCA jacks - can't screw in

I recently inherited a Sansui QRX-9001. It had been sitting for years so I wanted to clean it. I removed the cover and then I unscrewed the RCA jacks. My thought was to pull them out a little and check for rust or use the contact cleaner. Now, when I try to screw them back on, it's like there is nothing behind the screw holes for the screw to latch onto. I guess there was something there that fell away when I removed the screws. HELP. I don't want to ruin this beautiful machine.

Re: RCA jacks - can't screw in

Are they the type of RCA jacks that mount with nuts? If so, the nuts are inside. If not, then they are the type that is mounted to a phenolic board and aren't meant to be removed.