I am a little unclear about the recent history. You say you originally heard no problem with the right channel, only the left channel was without signal. And incidentally, you mention that only the L channel was grounded. When you replaced the fuses, did things get worse, in that you lost the R channel as well? It seems so, based on what you wrote.
Have you opened the chassis, at least to see by visual inspection whether there are any loose wires? The fact that only the L channel was grounded should be neither here nor there, because if you're talking about chassis to chassis grounding, the grounds are probably common to each channel. I don't think there is a problem with your transformer, because you would have heard nothing at all or something more catastrophic might have occurred, if the AC voltage coming out of your transformer is seriously off the mark. BUT do you perchance have an AC voltmeter with which you can check it?
Have you opened the chassis, at least to see by visual inspection whether there are any loose wires? The fact that only the L channel was grounded should be neither here nor there, because if you're talking about chassis to chassis grounding, the grounds are probably common to each channel. I don't think there is a problem with your transformer, because you would have heard nothing at all or something more catastrophic might have occurred, if the AC voltage coming out of your transformer is seriously off the mark. BUT do you perchance have an AC voltmeter with which you can check it?