I don't know why I am pursuing this, but Jea wrote, "The sound you said you could hear faintly through the bad channel of the phono preamp could be nothing more than cross talk from the good channel." I agree with Jea, and that was a good thought on his part (or her part). The fact that switching the wires at the cartridge resulted in just slightly more sound coming from the "dead" speaker is probably due to the fact that the crosstalk from channel B into channel A is greater in db than the crosstalk from channel A into channel B. This is commonly true unless azimuth has been meticulously adjusted.
Soooo. This means the speaker is not really "dead", because it can make sounds. It also means the cartridge is in fact fine, because it can drive the "good" speaker when its leads are switched. It also means that the OP needs to start swapping leads on down the chain of components that feed the speaker in question. At some point, the problem should switch sides, from one speaker to the other, and then the OP will have found his problem.
Soooo. This means the speaker is not really "dead", because it can make sounds. It also means the cartridge is in fact fine, because it can drive the "good" speaker when its leads are switched. It also means that the OP needs to start swapping leads on down the chain of components that feed the speaker in question. At some point, the problem should switch sides, from one speaker to the other, and then the OP will have found his problem.