From leaking batteries to bad capacitors to failing power supplies, Mac IIsis always require maintenance to remain in good working order. Read below to find out about what issues need addressing.
The Mac IIsi has many surface-mount (SMD) electrolytic capacitors on its logic board. These capacitors have a 100% failure rate and will leak a corrosive and conductive electolyte fluid over the board that will damage components and traces given enough time. These capacitors must be replaced for continued operation of any Mac IIsi. Capacitor reference information is available under the resources page, or directly through The Capacitor Reference Library.
The Mac IIsi uses a 1/2AA size Lithium battery for PRAM backup. This battery is not required on the IIsi for operation, and any original battery should be removed. These original batteries often leak, and can cause catastrophic damage that renders logic boards unfixably damaged.
The IIsi's PSU (made by Sony) is extremely unreliable. Much of this is due to its use of ELNA capacitors, which are some of the most leak-prone caps ever made (at least, their "LongLife" caps made during this time are. Their newer stuff is pretty good I believe). You haven't seen bad cap leakage until you've seen what these ELNA caps can do to a board. They MUST be replaced. That aside, they're unreliable even with new caps. My recommendation would be to replace the old supply altogether with a modern one if a recap alone doesn't fix your original unit.
Most original SCSI hard drives for these have gone bad, especially those made by Quantum, which suffer from sticky rubber bumpers in the head assembly.
The floppy drives in these often suffer from eject motor failures due to a gear that falls apart with age. This gear can be replaced without too much trouble.
The Mac IIsi's case yellows with age. A retrobrite process can be used to correct this, if it bothers you. The plastic is not nearly as brittle as Macs from the 90s though.
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