Try switching the cartridge leads left to right where they connect to the cartridge. If the channel imbalance switches channels, then you have a faulty cartridge (or something off in the cartridge set-up...perhaps azimuth).
If the channel imbalance doesn't follow the switch, then put the cartridge leads back to normal, and then switch your phono interconnects at the table by putting the left output into the right jack and vice versa. If the channel imbalance follows the swap, then the problem is in the tonearm. If the channel imbalance does not follow the swap, then the problem is downstream of the table.
Keep doing this process of switching one end of each successive interconnect pair (first normalizing the upstream interconnects) until you hear the channel imbalance switch channels. When it happens, you'll have found the component that's causing the problem.
Good luck.
If the channel imbalance doesn't follow the switch, then put the cartridge leads back to normal, and then switch your phono interconnects at the table by putting the left output into the right jack and vice versa. If the channel imbalance follows the swap, then the problem is in the tonearm. If the channel imbalance does not follow the swap, then the problem is downstream of the table.
Keep doing this process of switching one end of each successive interconnect pair (first normalizing the upstream interconnects) until you hear the channel imbalance switch channels. When it happens, you'll have found the component that's causing the problem.
Good luck.