Macintosh IIsi Troubleshooting
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Fault-finding for the Macintosh IIsi. The tables are Apple's symptom charts from the IIsi Service Source, with the cures in Apple's order: try the first, check whether the symptom persists, and if a module swap does not cure it, refit the original before moving on.[1] Apple's cures stop at module level; the known component-level faults follow the charts.
Power and start-up
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Screen completely dark, fan off, LED off | Plug the monitor into a wall socket and check it has power; remove the NuBus card and switch on again (Apple notes the card "draws more than 45 watts"); remove peripherals; power supply; logic board |
| Error chord at start-up | Check the SIMMs; logic board |
| Clicking, chirping or thumping | Power supply; disconnect the hard drive, and replace it if the noise stops; logic board |
| Shuts down intermittently | Clear the vents on the back and top of the case (thermal protection; runs again after 30-40 minutes); power cord; power supply; logic board |
| Crashes or locks up intermittently | System 6.0.7 or later; known-good software; remove extra RAM and NuBus cards; logic board; SIMMs; power supply |
| Restarts by itself | Turn the locking power switch on the rear to the unlocked (horizontal) position |
| Clock not running | Battery; reset PRAM; logic board |
| Boots, then "Finder is old version" | Clear PRAM; logic board |
Apple's chart for the error chord gives no codes. For the Sad Mac codes of the Macintosh II family, see Sad Mac Error Codes.
To clear PRAM under System 7, hold Command-Option-P-R at start-up before "Welcome to Macintosh" appears; under System 6, hold Command-Option-Shift while opening the Control Panel from the Apple menu.[1] A hard reset is Command-Control-Power, held for at least a second; the IIsi has no programmer's switch.[2]
Video
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Dark screen; audio and a drive working, fan and LED on | Monitor brightness; try the monitor on another Macintosh; monitor; video cable; video card; SIMMs; logic board; power supply |
| Dark screen; no audio or drive activity, fan and LED on | Try the monitor on another Macintosh; video cable; monitor; remove NuBus cards; remove peripherals; SIMMs; logic board; power supply |
| Screen bright, audio present, no picture | Try the monitor on another Macintosh; monitor; video cable; logic board |
The built-in video stops if the monitor is not one it recognises; it supports Apple's 12-inch and 13-inch RGB, 12-inch monochrome and 15-inch portrait monitors, identified by the sense pins on the DB-15.[2] A black screen on another monitor is not by itself a fault.
Floppy and hard drives
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Internal floppy drive does not work | Floppy cable; floppy drive; logic board |
| Disk ejects and a Mac icon with a blinking X appears | Another disk; floppy cable; floppy drive; logic board |
| Disk will not eject | Switch off and hold the mouse button down while switching on; eject manually; floppy drive |
| Drive tries to eject but fails | Push the disk fully in; take the top cover off and try again; eject manually; floppy drive |
| Hard drive runs continuously | Hard drive data cable; hard drive; logic board |
| Hard drive does not work | Data cable; power cable; hard drive; logic board |
| Works with the internal drive or an external SCSI device, not both | External device must have a different SCSI ID; external terminator; the internal drive must have a terminator; SCSI select cable |
See Macintosh Floppy Drive Maintenance and Macintosh HDD Maintenance.
Keyboard, mouse and printing
[edit | edit source]| Symptom | Apple's cures, in order |
|---|---|
| Cursor does not move | Restart; mouse connection; connect the mouse to the computer's ADB port without the keyboard, and replace the keyboard if it then works; mouse; remove NuBus cards; logic board |
| Cursor moves, clicking does nothing | Mouse; logic board |
| Double-click does not open anything | Remove duplicate System files; clear PRAM; check keyboard and mouse as above; logic board |
| No response from the keyboard | Keyboard connection; keyboard cable; keyboard; logic board |
| ImageWriter will not print | System 6.0.7 or later; Chooser and Control Panel settings; printer DIP switches; reset PRAM; printer cable; logic board |
| LaserWriter will not print | System 6.0.7 or later; Chooser and Control Panel settings; reset PRAM; networking |
The keyboard power key starts the IIsi through ADB pin 2, which must be grounded briefly to pin 4; with a dead keyboard or cable, use the power switch on the rear panel.[2]
Sound
[edit | edit source]Apple's chart for no sound from the speaker is: volume in the Control Panel at 1 or above; reset PRAM; speaker; logic board.[1]
The usual cause is the speaker contacts. The speaker assembly connects to the logic board through metal fingers, and when they corrode the internal sound cuts out, sometimes only after the machine has run for hours, while headphones still work. Take the speaker assembly out, clean the contacts with isopropyl alcohol, and treat them with a contact preservative if you wish.[3][4] Apple's route to the speaker is cover, adapter card, fan, power supply, hard drive and logic board, then the LED and four clips; on reassembly the speaker's fingers must touch the contacts under the logic board.[1] See Macintosh IIsi General Maintenance.
Known faults
[edit | edit source]Leaking capacitors
[edit | edit source]Recap-a-Mac found leaking capacitors on the logic board and in the power supply, and says the Sony APS-06M supply is "extremely prone to leakage".[5][6] See Macintosh IIsi Capacitor Replacement Guide.
Battery
[edit | edit source]Apple's threshold is 3.0 V on the 10 V DC range.[1] A leaking cell corrodes the board around its holder; neutralise lithium residue with bicarbonate of soda, not vinegar. See Battery Explosion, Capacitor or Corrosion Damage.
No FPU
[edit | edit source]The 68882 is on the NuBus and direct-slot adapter cards, not the logic board, so a IIsi without an adapter has no FPU and software that needs one will not run.[2]
Related pages
[edit | edit source]- Macintosh IIsi
- Macintosh IIsi General Maintenance
- Macintosh IIsi Capacitor Replacement Guide
- Sad Mac Error Codes
- Capacitor Failure Symptoms
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 Apple Computer, Macintosh IIsi Service Source (1995), File:Macintosh iisi.pdf; see Macintosh IIsi Service Source. Troubleshooting, PDF pp. 14-28: General p. 14; Video pp. 15-17; Floppy Drive pp. 18-19; Hard Drive p. 20; Peripheral pp. 21-24; Miscellaneous pp. 25-27; Error Chords p. 28.
- ↑ 2.0 2.1 2.2 2.3 Apple Computer, Macintosh IIsi Computer Developer Note (1990), File:Macintosh IIsi Developer Note.pdf; see Macintosh IIsi Developer Note. PDF p. 41 (unknown monitor halts video); pp. 62-66 (ADB microcontroller, +5 V trickle, soft power, power switch lock, keyboard reset and NMI); p. 70 (FPU on the adapter cards only).
- ↑ 32 How can I fix the sound on my IISI?, TULARC—link(accessed 2026-09-30)
- ↑ Mac IIsi, Low End Mac—link(accessed 2026-09-30) Internal speaker failure usually from poor contact, fixed by cleaning and treating the contacts.
- ↑ Macintosh IIsi, Recap-a-Mac—link(accessed 2026-09-30)
- ↑ Macintosh IIsi Power Supply, Recap-a-Mac—link(accessed 2026-09-30)