Is this safe?

Hello, all.

I have a Line Magnetic 515 cd player, which I enjoy.  It has two tubes (6kz8).  I had heard some users enjoy rolling the tubes, and so today I tried rolling in some Amperex tubes.  It didn't sound very good--bright and thin--and now I would like to go back to the Raytheon tubes that came with the unit.  So I powered it off and unplugged it.  But how long do i need to wait before I can open the unit up without a risk of shock?  Thanks!  Margot