How to test a cartridge?

I think either the preamp or the cartridge have problem.

I suggest you to connect the right phono cable(the one with sound) to the left input in your preamp(phono input) and the left to the right. If there is sound from the left but no sound from the right. Then the is a problem with the cartridge.

If there is no sound from the left and sound from the right side, then the problem is in your preamp.

Edle, though I think Consttraveler's cartridge test might cast some doubt on the cart being the problem, his swapping-out the preamp and phono preamp eliminates the preamps from being the problem. Consttraveler, since you say you swapped out all the IC's plus the TT, I will assume that there is no wire, including headshell leads, tonearm wire, etc. in common. If so, this is a stumper for sure, but I would take the additional step of hooking up the cartridge with the headshell leads reversed left for right, just to double-check on your meter-reading test, since it appears that your cart is the only common denominator.

Consttraveler, you say you changed turntables? This I find a bit confusing. Do you mean, you removed your arm plus cart and mounted it on another turntable?? Why that? Did you check your cartridge leads to the phonopreamp with your ohmmeter? Do both carry signal? If yes, do as Zaike suggests and let us know how it goes. Good luck!