try plugging the tt to a different input--it will be soft but you should be able to hear if it still happens if you turn it up.
if still there--most likely the tt/cable/cart--not sure if the cart can be replaced on that model or not--alternately make sure the pins on the back of the cartridge are snug but the output cable could be bad as well. given the issue my guess would be the cartridge or the connection to the cable behind it. let us know how it works out. good luck
if still there--most likely the tt/cable/cart--not sure if the cart can be replaced on that model or not--alternately make sure the pins on the back of the cartridge are snug but the output cable could be bad as well. given the issue my guess would be the cartridge or the connection to the cable behind it. let us know how it works out. good luck