The capacitor is just a smoothing capacitor on the -5V supply. I think the -5V supply is only used for the printer (appletalk) and modem port drivers. Since the aluminium can capacitors which were on the LCIII as they came out of the factory did not cause a failure I wouldn't worry about LCIIIs which haven't been recapped.
I have no idea how other LCIIIs that have been recapped have stood up. It seems that tantalum capacitors are the favourite ones to use for the recap. The tantalum that I put in facing the way the original silkscreen showed, failed by starting to go short circuit. It was dragging about 1.3A from 75mA the -5V supply and dragged it down to -2.1V. I have no idea which would have broken first, the power supply or the capacitor, if I left it going for longer. I doubt whether the Modem or Printer ports would work properly with a -2.1V supply.
Maybe the tantalums other people are using to recap their boards are more tolerant of being reverse biased.
I am not a Mac user but I was, in the early 1990's, when we made the machine which was controlled by the LCIII that I am trying to back up. So I know nothing of how the PCB layout changed with subsequent Macs.
I have no idea how other LCIIIs that have been recapped have stood up. It seems that tantalum capacitors are the favourite ones to use for the recap. The tantalum that I put in facing the way the original silkscreen showed, failed by starting to go short circuit. It was dragging about 1.3A from 75mA the -5V supply and dragged it down to -2.1V. I have no idea which would have broken first, the power supply or the capacitor, if I left it going for longer. I doubt whether the Modem or Printer ports would work properly with a -2.1V supply.
Maybe the tantalums other people are using to recap their boards are more tolerant of being reverse biased.
I am not a Mac user but I was, in the early 1990's, when we made the machine which was controlled by the LCIII that I am trying to back up. So I know nothing of how the PCB layout changed with subsequent Macs.