Hi,
It sounds as if you have lost one side of the amp or input, checkout the the valve base type connector on the mechanism/carousel and the phono cables that are soldered to the back of the socket. Make sure the cartridge is wired one side out of phase if you have the 64 watt Rowe Ami amplifier in the jukebox (601-02179 or 2179).
The bass goes across both channels and the top range is across a channel and ground.
Regards
Alan Hood
ami-man
UK