Mono Problem?

Genletmen, I just installed a new Nagaoka cartridge MP-200. Sounds great. However, when I play a mono disc I normally have the mode selector on my preamp switched to 'mono'. So when I do that with the Nagaoka installed their is no sound. Switch back to stereo, sound, mono no sound. I have checked and re-checked the wiring, all is good. Anyone ever experience this with a stereo cartridge? Suggestions? I really like the sound of this cartridge and would like to use it.
Sure sounds like one channel is wired out of phase (hot and ground interchanged), even though you checked the connections carefully. Maybe the cartridge itself is miswired, or its color-coding is misleading.

What happens if you listen to a stereo recording in stereo mode, that should have a soloist centered between the speakers? Do you get a sharply defined image in the center, or a diffuse, hard-to-localize image (which would be further confirmation that one channel is wired out of phase)?

-- Al

You are spot on! This is a secondary table that I am using and the headshell wiring is incorrect! I am stunned that I never noticed before, as I use this system for background music in my home office. All is good. (its been like that for years)

Thanks so much Al.