My bass amp is crazy, what's wrong? Snap Crackle Pop!?

I have an old 70's Acoustic bass amp which has gone crazy. When i power up i don't get any sound right away(although very faint sound if i turn up bass volume all the way) After amp on for about 10 min speakers start to snap crackle and pop and the noise builds up until i get one last loud pop and then i get sound and works fine.
If I were to shut it off and turn it back on, i get sound ok but if its off for more than 5 or 10 min then it goes thru the whole snap crackle pop routine before sound comes back.
Has Jaco haunted my bass rig? Please help.

Ed
November 2008