They really are solid on sideband, and loud in either mode, SSB or Am. Mine is unmodified, and one of my favorite old rigs to play on. I usually pair it with a KLV tube amp, and make lots of DX contacts. I am told they have a compressor built into the mic circuit, so just about any mic sounds great on them. The Turner really kicks it up a notch! Glad you got yours fixed, like I said, mine had the exact same problem.
73 and good DX,
RT307