Canon's EOS 5 has a few other known problems that affect the LCD display, display drivers and power circuit, quite apart from its well known penchant for prematurely exhausting the 2CR5 battery.
The most common repair for the 5 is (and is likely to remain) interventional rather than remedial. Derangement of the internal and external displays through persistent exposure to high humidity and rain (through seepage) is well known, and is all too often mistaken for a bad battery. Also a problem is prolonged exposure in, for instance, seaside environments. The EOS 5 has very poor sealing from the elements — something that needs to be considered when using it in what is termed adverse conditions. Displays affected by humidity or a display driver circuit will manifest as gradual fading to nothing when used in conditions that favour it, returning to a visible display when humidity drops. Some twits have put their camera in a moderately hot oven to speed up the "recovery", only to introduce more problems so profound as to render the camera useless!
This nasty display problem cannot be remedied through service, which usually involves, to the best possible degree, re-soldering of affected circuit bridges, replacement as needed of display driver components (this can often exceed the value of the camera itself) and reassembly with little useful repatriation of what limited body sealing had existed. The best solution is to buy a camera that has much better sealing and more robust circuitry e.g. EOS 1N, EOS 1V or the EOS 33. Repeated exposure to salty environments (beaches) will affect most cameras, more dramatically so where lenses are frequently changed.
