Macintosh LC Troubleshooting: Difference between revisions
Create Macintosh LC troubleshooting guide |
Expand troubleshooting: exploding PRAM battery, SMD-cap leakage (chime-but-no-video), PSU recap; cited (68kMLA/Quagmire/Service Source) |
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The LC is particularly prone to audio issues due to its plastic audio jack sockets, which are near capacitors that commonly leak. | The LC is particularly prone to audio issues due to its plastic audio jack sockets, which are near capacitors that commonly leak. | ||
== ⚠️ PRAM battery — remove it now == | |||
The Macintosh LC uses a 3.6 V 1/2AA lithium PRAM battery (often a red Maxell). These are notorious for '''leaking and even exploding''', spraying corrosive electrolyte across the logic board — a battery can burst while the machine sits in storage and destroy the board. '''Remove the PRAM battery from any un-serviced unit immediately.''' If one has leaked, neutralise and clean the residue and check the traces and vias around the battery and the nearby chips for corrosion, repairing any that are damaged.<ref name="lc_batt">[https://68kmla.org/bb/threads/warning-exploding-maxell-pram-batteries.25169/ "Warning! Exploding Maxell PRAM Batteries"], 68kMLA; and [https://www.macdat.net/repair/kb/batteries_macintosh.html "Mac Battery Leaks"], MacDat. Source for the exploding/leaking Maxell PRAM battery and the resulting board damage, and the LC not booting without a battery.</ref> | |||
The LC-series machines are also well known for '''not booting without a healthy PRAM battery'''. A dead or removed cell can leave the machine apparently dead or refusing to chime, so fit a fresh battery (or a modern coin-cell replacement) when testing.<ref name="lc_batt">[https://68kmla.org/bb/threads/warning-exploding-maxell-pram-batteries.25169/ "Warning! Exploding Maxell PRAM Batteries"], 68kMLA; and [https://www.macdat.net/repair/kb/batteries_macintosh.html "Mac Battery Leaks"], MacDat. Source for the exploding/leaking Maxell PRAM battery and the resulting board damage, and the LC not booting without a battery.</ref> | |||
== ⚠️ Surface-mount capacitor leakage == | |||
The Macintosh LC logic board uses surface-mount electrolytic capacitors that leak electrolyte from the bottom with age. The leakage corrodes traces and vias and is a leading cause of faults, so '''recap and clean the board''' as a first step. A common pattern is a board that '''chimes but shows no video''' after servicing — usually corrosion damage (broken traces or vias) around the leaked capacitors (for example near C136/C137), which must be traced and repaired.<ref name="lc_cap">[https://quagmirerepair.com/quadra605 "Quadra 605 / LC 475"], Quagmire Repair; the Apple Macintosh LC/LC II/LC III/LC 475/Quadra 605 Service Source; and [https://pappp.net/?p=1530 "Macintosh LC Recap"], PAPPP's Rambling. Source for the SMD-capacitor leakage, the PSU recap, and the trace/via damage causing chime-but-no-video.</ref> | |||
== Power supply == | |||
The compact LC "pizza-box" power supply also uses electrolytics that leak with age. A '''dead LC PSU can usually be revived by replacing all its electrolytic capacitors''' and cleaning the leakage; any working LC PSU should be recapped pre-emptively, as it will otherwise fail. Confirm the +5 V and +12 V rails after servicing.<ref name="lc_cap">[https://quagmirerepair.com/quadra605 "Quadra 605 / LC 475"], Quagmire Repair; the Apple Macintosh LC/LC II/LC III/LC 475/Quadra 605 Service Source; and [https://pappp.net/?p=1530 "Macintosh LC Recap"], PAPPP's Rambling. Source for the SMD-capacitor leakage, the PSU recap, and the trace/via damage causing chime-but-no-video.</ref> | |||
== References == | |||
<references /> | |||
== Related Pages == | == Related Pages == | ||