Macintosh LC 475 - Common Faults & Maintenance

From leaking batteries to bad capacitors, Mac LC 475s require maintenance to remain in good working order. Read below to find out about what issues may need addressing.

Capacitors

The Mac LC 475 has many surface-mount (SMD) electrolytic capacitors on its logic board. These capacitors have a near 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 LC 475. Capacitor reference information is available under the resources page, or directly through The Capacitor Reference Library.

The LC 475's Power Supply can also be problematic. They shipped with supplies from three vendors - Astec, TDK, and Dyna Comp. All three can be prone to bad or leaking capacitors, but the TDK unit is the worst of the three. It used ELNA LongLife series caps which are probably the most leak-prone through hole caps from the time. These can cause a real mess, so any TDK PSU is a recap on sight. The Astec supplies are better but still can experience issues. Recap if you're having power trouble. The Dyna Comp unit also has cap leaks but I don't know how common they are.


PRAM Battery

The LC 475 uses a 1/2AA size Lithium battery for backing up the computer's PRAM. The original 30+ year old batteries are prone to leaking severely in their age and need to be removed immediately from any LC 475.

Unlike most other Macs, the battery must actually be replaced for an LC 475 to work. Without one, it will not output video. You can get around this by rapidly flipping the power switch on boot, but this isn't a good long-term solution, and probably isn't good for either the switch or the power supply. Install a new battery.


Other Notes

Many 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. They also suck in tons of dust, so a good cleaning is in order for just about any unserviced unit.

The Mac LC 475's case yellows with age. A retrobrite process can be used to correct this, if it bothers you.



Page last updated (MM/DD/YYYY): 04/19/2024
Update Reason: added newnav

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