I am at the end of my rope, please help

You posted on VA as well, and I took a shot at it there. But now I see something that eluded me previously. You say both here and on VA that you took your measurements directly off the tonearm wiring. I now see also that you changed BOTH your tonearm AND cartridge, and the problem persisted. If you did these two things simultaneously, that's whacky. Now I see why John Ellison focused in on your ICs. IF you have been using the same pair of ICs throughout, try another set whilst keeping the second tonearm/cartridge combo in place, or simply swap connections at both ends of both ICs, one end at a time. (IOW, at the tonearm end, swap leads between L and R channels. Listen. If the weak channel does not swap sides, then swap leads between L and R channels at the preamp end. Listen.) This will turn out to be something simple and benign, I am sure. Well all of are giving just about the same advice. So we cannot be wrong, can we?

Try reversing the polarity of one side of the cartridge i.e the right-hand side,at the cartridge.Then reverse the polarity at the right-hand speaker to return to correct polarity for playback and then take your measurements again.This is an old tweak from the glory days of vinyl to help minimise fluctuating polarities that occur inside amplifiers.It is something I do that has improved the fidelity of my vinyl playback.It just might address your problem.

Thank you all for the advice. This all happens before the phono stage so we can eliminate that as a problem. I think, based on how confusing this is, I may be having two problems at the same time. One looks like it may be a cartridge problem. When I use my meter to check the tonearm wires, the positive goes to positive and negative goes to negative BUT when I hook up the cart each wire goes to both positive and negative of the RCA plug. In other words, red lead goes to both positive and negative on the RCA plug and the green lead goes to both positive and negative on the RCA. The same thing happens on the other side. When I remove the cart and touch my meter to the the red and green pins I get a complete circuit. When I touch the white and blue pins on the cart I get a complete circuit. I don't think that should be happening. when I do the same to my backup MM cart I do not get a complete circuit. I am thinking that the cart has a short. Seems a little strange that it would be on both sides but my question is, Before I spend thousands on a new cart, is there any difference between a MM cart and a MC cart that would cause a complete circuit on an MC and not on an MM? Am I supposed to get a complete circuit?

I never enjoy being the bearer of bad news, but I would absolutely not put an ohmmeter across a phono cartridge, or across a cable that is connected to a phono cartridge, especially a low output moving coil. The meter measures resistance by measuring how much current flows through whatever it is connected to, in response to a voltage it applies through its own internal resistance. That current will be very small in relation to the current-carrying capabilities of most devices or circuits that might be measured, but I see no grounds for confidence that it won't be large enough to cause damage to a lomc.

Is there any difference between a MM cart and a MC cart that would cause a complete circuit on an MC and not on an MM?

Since there are far fewer turns in the coils of a lomc compared to a mm, the resistance will be much less in a lomc. As a very rough ballpark guess, perhaps a few ohms in the case of the lomc, and many hundreds of ohms or more in the case of a mm. Depending on the resolution of your meter, and the resistance scale you are using, the resistance of the lomc may be low enough to appear to be a short even though it is not.

Regards,
-- Al

Would demagnetising the cartridge help? There is a way to do this manually using the RCA's of the tonearm across each other (30 secs.),first one way then the other,the centre pin of one crossing the pin and shield of the other.Also it is not uncommon for there to be a difference in channel output even in new cartridges.From my position I would demagnetise and then listen to the playback with and without the tweak I suggested earlier.You should hear a clear difference and decide what to do from there.