So my birth day was about a month ago, and last saturday (or was it friday

) i got a Crate BX160 from my dads friend for free!

So the thing sounds great and has a pretty kick A-- Chrous built in, not to mention that the thing sounds killer through my GK 8x10. (makes my entire apartment rumble if i put my Pbass on full bass and tune the amp's EQ correctly) well anyways... It has a bad buzz. The second you turn the amp on... BZZZZZ... you can hardly hear it when playing it, but when your not all you here is buzzing. I dont have the 1x15 speaker in it (as it doesnt work) but im buying a new one soon. BUt does anyone else have this problem with this amp? If so do you know how to fix it? My dad and I tried lifting the ground and it didnt work >.< So any suggestions are welcomed and if anyone has an inside tips on how to get the buzz gone it would be great! If you need a Picture i am more then willing to take one and post it on here for you guys!
thanks!