I gave my Beogram RX2 turntable to my father since he still likes vinyl.  We hooked it up to his Pioneer Stereo Receiver SX202.  The MM5 cartridge is installed correctly and the ground and RCA from the turntable are installed correctly.  But we get a very nasty ground hum that kicks on and off at whim; and sometimes the whim is rather long.  Does anyone know how I can trouble shoot/repair this?