Macintosh LC II Troubleshooting
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Fault diagnosis for the Macintosh LC II and the Performa 400, 405, 410 and 430. The tables follow Apple's symptom charts for the LC series, which list cures in order of likelihood: try the first cure first, and if you replace a module and the symptom stays, refit the original before moving to the next cure.[1]
Before you start
[edit | edit source]- Apple publishes no rail voltages or tolerances for the LC-family supply (part 661-1733) and no adjustment; its charts end in replacing the supply as a module.[1]
- Apple's charts check the PRAM battery for a dark screen with a working drive and for a machine that intermittently fails to power on. The battery is a lithium cell, part 742-0011; Apple replaces it below 3.0 V.[1]
- The LC II has no programmer's switch. Command-Power sends an NMI and Command-Control-Power forces a hard reset; hold the keys for at least a second.[2]
Startup sounds and dark screen
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Eight-tone error chord at startup | Replace the SIMMs; check the SIMMs in the replacement board; replace the logic board, keeping the customer's SIMMs |
| Four-tone error chord at startup (LC II) | Disconnect the hard drive power and data cables and reboot: if startup is normal, test the drive with Macintosh Hard Disk Test and replace it if necessary. Disconnect the floppy cable and reboot: if startup is normal, replace the floppy drive. Then replace the logic board |
| Screen dark, audio and at least one drive working, fan runs, LED lit | Adjust the monitor brightness; try the monitor on another Macintosh; check the battery; replace the monitor; replace the video cable; replace the VRAM SIMM; replace the logic board; replace the power supply |
| Screen dark, audio and drives not working, fan runs, LED lit | Remove any expansion card; remove peripherals; disconnect the hard and floppy drives; replace the SIMMs; replace the logic board; replace the power supply |
| Part or all of the screen bright, audio present, no picture | Try the monitor on another Macintosh; replace the video cable; replace the monitor; replace the logic board |
| Screen completely dark, fan not running, LED not lit | Plug the monitor directly into the wall and check it has power; remove any expansion card; remove peripherals; disconnect the hard and floppy drives; replace the power supply; replace the logic board |
| Lines or snow, or a dark screen with a normal startup tone | Try the monitor on another Macintosh; replace the video cable; replace the monitor; replace the VRAM SIMM; replace the logic board; replace the power supply |
If a Sad Mac appears, Sad Mac Error Codes explains how to read the two lines of the code.
Intermittent faults
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| System shuts down or restarts intermittently | Clear the vents on the back and top of the case (thermal protection may shut the computer down; it should be OK after 30 to 40 minutes); replace the power cable; fit the standoffs on an LC Ethernet card; replace the power supply; replace the SIMMs; replace the logic board |
| System intermittently does not power on | Check the cables; plug the monitor directly into the wall; try a known-good keyboard and ADB cable; replace the power cord; check the battery; replace the logic board |
| System intermittently crashes or locks up | Use System 7.0.1 or later; check the software; replace the logic board; replace the SIMMs; replace the power supply |
| Clicking, chirping or thumping | Disconnect the hard drive and replace it if the noise stops; replace the power supply; replace the logic board |
| Clock does not run | Replace the battery; reset the PRAM; check nothing is connected to the sound-out port; replace the logic board |
An LC Ethernet card fitted without its short and long standoffs can make the computer restart intermittently; Apple's upgrade procedure fits both.[1]
Drives
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Audio and video present, internal floppy drive does not operate | Replace the floppy cable; replace the floppy drive; replace the logic board |
| Disk ejects; Mac icon with blinking X | Try a known-good system disk; replace the floppy cable; replace the floppy drive; replace the logic board |
| Disk does not eject | Hold the mouse button down while switching on; remove the top cover; eject manually with a straightened paper clip in the hole beside the slot; replace the floppy cable; replace the floppy drive |
| Drive tries to eject but does not | Push the disk fully in; eject manually with a paper clip; check the cover is fully on; replace the floppy drive |
| Internal hard drive runs continuously | Use System 7.0.1 or later; replace the hard drive cable; replace the drive; replace the logic board |
| Internal hard drive does not operate | Replace the data cable; replace the power cable; replace the drive; replace the logic board |
| SCSI device works internally or externally but not both | Set a different SCSI ID on the external device; terminate both ends; replace the terminator; check the terminator on the internal drive; replace the SCSI cable |
See Macintosh Floppy Drive Maintenance and Macintosh HDD Maintenance.
Sound, keyboard and printing
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| No sound from the speaker | Set the volume in the Control Panel to 1 or above; reset the PRAM; check nothing is plugged into the sound-out port; replace the speaker; replace the logic board |
| No response from the keyboard | Use System 7.0.1 or later; check the ADB connection; replace the keyboard cable; replace the keyboard; remove the battery for 15 to 30 minutes to reset the logic board; replace the logic board |
| Cursor does not move | Reboot; check the mouse connection; try the mouse in the rear ADB port without the keyboard; replace the mouse; remove extra PDS cards; reset the PRAM; replace the logic board |
| "Finder is old version" at boot | Clear the PRAM (Command-Option-P-R at startup under System 7); replace the logic board |
| Known-good printer does not print | Check the Chooser and Control Panel settings; use System 7.0.1 or later; reset the PRAM; for an ImageWriter, check its DIP switches and cable |
Things that are not faults
[edit | edit source]- The LC II addresses only 10 MB of RAM even with 12 MB fitted.[1]
- Both sound channels carry the same signal: Apple's sound generator on the LC II is monophonic.[1]
- The LC II has no FPU, so software that requires one will not run.[1]
Capacitors and battery damage
[edit | edit source]The LC II logic board, 820-0327-A, has seventeen surface-mount electrolytic capacitors, and Recap-a-Mac says all of them need replacing.[3] Check continuity around each position after removing the old parts. A leaking PRAM cell corrodes the board around its holder. See Macintosh LC II Capacitor Replacement Guide, Capacitor Failure Symptoms and Battery Explosion, Capacitor or Corrosion Damage. The shared power supply's capacitor lists are on Macintosh LC Capacitor Replacement Guide.
Related pages
[edit | edit source]- Macintosh LC II
- Macintosh LC II General Maintenance
- Macintosh LC II Capacitor Replacement Guide
- Sad Mac Error Codes
References
[edit | edit source]- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Apple Computer, Macintosh LC Series/Quadra 605 Service Source, File:Quadra 605.lc series.pdf (see Macintosh LC Series/ Quadra 605 Service Source): Troubleshooting, general notes and symptom charts, PDF pp. 19-36; Take Apart, PDF pp. 38-63; Battery Verification, PDF pp. 106-107.
- ↑ Apple Computer, Macintosh LC III Developer Note (1993), File:Macintosh LC III Developer Note.pdf, chapter 1, p. 29, "Keyboard Reset and NMI", which says these functions are "accessible from the keyboard as they are for the Macintosh LC and LC II".
- ↑ Macintosh LC II (Performa 400), Recap-a-Mac—link(accessed 2026-09-30) Annotated photograph of logic board 820-0327-A; "17 surface mount electrolytic capacitors that need replacing".