Well, if there are still any of these out there still working, it must be a miracle, or the owner has the patience of a saint!
Back in the 80's I foolishly bought one of these but after a year I traded it in for a Trio 9500, a solidly built rig that was reliable. What a mistake buying the Multi 750E was! It was always developing faults, intermittent faults that when you opened it, you could never find. The usual trick was to tap around the boards until the fault came and went, then you looked for the dry joint to resolder. It was usually on a terminal post or connector as they were never heated up enough during the flow solder processes used in those days by FDK, so they developed dry joints quickly and often.
I remember many other ham's complaining bitterly about the 700E, 725X, 750E, etc as they were suffering the same frustrations, going back to the emporium they bought them from and getting frustrated when they would not take the rig back because it had been used! These days, with consumer protection laws, you'd be returning it to the shop for a refund, because it was not fit for the purpose for which it was sold! I also still have a Multi 725X, picked up cheaply at a rally in a moment of madness and nostalgia, which suffers the same problems, so it reminded me to put this write up on here to warn others!!!