Macintosh LC II General Maintenance

Macintosh LC II logic board 820-0327 with every electrolytic marked. Source: Recap-a-Mac.

Routine care for the Macintosh LC II (logic board 820-0327-A, 1991), which Apple also sold as the Performa 400, 405, 410 and 430. The chassis, power supply, battery and take-apart procedure are shared with the rest of the LC "pizza box" family; the logic board is not.

The machine

Apple's specification for the Macintosh LC II

Item	Figure
Processor	Motorola 68030 at 16 MHz, 16-bit internal data bus, burst-mode RAM access
DRAM	4 MB standard, expandable to 10 MB (100 ns or faster SIMMs)
ROM	512K
VRAM	256K SIMM, upgradable to 512K
Expansion	96-pin PDS for an 020 or 030 direct-slot card
Sound	Mono 8-bit input; monophonic 8-bit generator feeding both channels
Power	100–240 V AC, automatically configured, 47–63 Hz; 50 W maximum, not including the monitor

Three limits in Apple's documents are not faults: the LC II addresses only 10 MB even with 12 MB fitted; it has no FPU socket (Apple lists one only for the LC III); and its sound output is mono. The LC II keeps the LC's 16-bit data path. Apple limits a card in the processor-direct slot to 4 W (800 mA at +5 V).

Opening the case

1. Disconnect everything.
2. Remove the case screw, if one is fitted.
3. Lift the tabs at the back of the lid and lift the top cover straight up.

To take out the logic board, remove the fan, disconnect the hard drive power and data cables, the floppy, power supply, fan and speaker cables, and remove any expansion card. Make sure the power button clears the rear panel, spread the two latches, push the board towards the front of the case and lift it out without touching the connectors on its underside.

Power supply

The LC, LC II, LC III, LC III+, LC 475 and Quadra 605 all use the same power supply, Apple service part 661-1733; the LC III+ is in Apple's Performa 400 Series manual, as the Performa 460, 466 and 467. Its input is 100–240 V AC, automatically configured, so there is no voltage selector. The 50 W figure is the LC II's maximum consumption, not the supply's rating.

Apple publishes no rail voltages, tolerances or adjustment for this supply; its power-related symptom chart entries end in replacing the supply. The "+5 V 4.85–5.15 V / +12 V 11.9–12.7 V" table seen on other pages is Apple's Macintosh Plus procedure and does not apply here.

To remove the supply, disconnect its cable from the logic board, release the two latches that hold its front end to the bottom case, and lift it out. The supply can be opened and recapped. With the cover off and the lead in, its primary side is at mains potential, and the reservoir capacitor charges to the peak of the mains waveform and keeps a charge after the plug is pulled; unplug it, wait, and measure across the reservoir capacitor before working near the primary side. Console5's capacitor lists for the six versions, from three makers, are on Macintosh LC Capacitor Replacement Guide.

PRAM battery

Apple's exploded view lists a lithium battery, part 742-0011, in a holder on the logic board; EveryMac gives it as 3.6 V. Apple's check is a measurement: set the meter to the 10 V DC range, probe the ends of the cell, and replace it if it reads below 3.0 V. To remove it, push a small flat screwdriver into the top of the holder until the side tab releases, repeat at the other end, lift off the cover and take the cell out. Apple gives no replacement interval.

If the cell has leaked, neutralise the residue with a paste of bicarbonate of soda and distilled water (the cell is lithium), rinse with distilled water, follow with isopropyl alcohol and dry thoroughly. Check continuity on every track leaving the holder and look at the underside of the board. See Battery Explosion, Capacitor or Corrosion Damage and Battery Refurbishment.

Take the cell out before the machine goes into storage.

Cleaning

• Blow dust out of the logic board, the power supply and the fan, and clean grime with isopropyl alcohol and a soft brush.
• Clean the case with a damp cloth and mild detergent; no abrasives or solvents.
• For yellowed plastics, see Retrobrite.

Keep the vents on the back and top of the case clear. Apple's chart for a machine that shuts down or restarts intermittently starts with the vents: thermal protection circuitry may shut the computer down, and it should recover after 30 to 40 minutes.

Fan and speaker

The LC II has a separate fan with its own cable: disconnect the cable from the logic board, release the plastic latches and lift the fan out. Apple's replacement caution is to fit the fan logo side down, "or the fan may damage the computer".

The speaker is also separate. When refitting it, thread its cable through the top two brackets that hold the hard drive before reconnecting it.

Connectors and sockets

Oxidised contacts cause intermittent faults on machines of this age. Clean and reseat the RAM SIMM sockets, the VRAM SIMM socket, the expansion slot, the logic board power connector and the SCSI and floppy connectors. Do not use an abrasive on SIMM contacts: it removes the plating. A contact cleaner such as DeoxIT D5 is for contacts that are actually corroded.

After any work near the back of the board, check that the sound-out and sound-in plugs go into the right ports; Apple warns that the wrong port can damage the computer or the equipment.

Capacitors

Logic board 820-0327-A has seventeen surface-mount electrolytics: ten 10 µF 16 V, five 47 µF 16 V, one 100 µF 6.3 V and one 1 µF 50 V. That is a different set from the original LC's fifteen. Designators, the board photograph and the procedure are on Macintosh LC II Capacitor Replacement Guide.

The LC III's reversed capacitor is at C22. The LC II's C22 is a 1 µF 50 V part in a different place and nothing is wrong with it. See Macintosh LC III Capacitor Replacement Guide.

Floppy drive

Apple's replacement notes: remove the dust shield, if present, before fitting a replacement auto-inject SuperDrive, and replace drives like for like, since some machines have a manual-eject drive. For a disk that will not eject, Apple's first step is to hold the mouse button down while switching on; next, remove the top cover and eject the disk with a straightened paper clip in the hole beside the slot. See Macintosh Floppy Drive Maintenance.

Hard disk

The internal drive is SCSI. Apple's chart for a device that works internally or externally but not both checks that the external device has a different SCSI ID, that both ends of the chain are terminated, and that a terminator is fitted on the internal drive. See Macintosh HDD Maintenance.

Related pages

• Macintosh LC II
• Macintosh LC II Capacitor Replacement Guide
• Macintosh LC II Troubleshooting
• Macintosh LC Series/ Quadra 605 Service Source
• Macintosh LC II Developer Note
• Recommended Tools