Power Macintosh 8100 General Maintenance

Power Macintosh 8100/80AV logic board out of the case. Photo: Stephen Edmonds, Wikimedia Commons, CC BY-SA 2.5

These procedures for the Power Macintosh 8100 come from Apple's Power Macintosh 8100/WS 8150 Service Source, which covers the 8100/80, 8100/80AV, 8100/100, 8100/100AV and 8100/110 and the Workgroup Server 8150. The 8100 uses the Macintosh Quadra 800 minitower case, and the logic board has to come out of it before the clock battery can be tested or changed (SS p. 94). Dan Knight of Low End Mac, quoted by Wikipedia, wrote that changing anything on the motherboard required removing it completely. Apple's take-apart steps call for a grounding wrist strap (pp. 62–88).

The power supply carries mains voltage whenever the computer is plugged in. Unplug it before opening the case.

Opening the case

Loosen the four captive screws on the rear panel, slide the top housing forward about half an inch and lift it off. Take care not to deform the metal dome-shaped shield inside the housing (SS p. 61).

Drives

• Hard drive: disconnect its SCSI and power cables, press down the retaining clip and slide the drive out (pp. 64–66).
• CD-ROM drive: disconnect the SCSI, audio and power cables, pull up the retaining clip and slide it out (pp. 67–69).
• Floppy drive: remove the CD-ROM drive first, press down the floppy drive's retaining clip, slide the drive forward about 2 inches, disconnect its cable and lift it out (pp. 62–63).

The logic board has two internal SCSI connectors. In Apple's standard layout the upper one serves the CD-ROM and tape drives and the lower one, below the DRAM and above the reset/interrupt switch, serves the hard drive (p. 65). The external port supports six devices, or five with an internal CD-ROM drive (p. 28). Apple's CD-ROM upgrade sets the drive to SCSI ID 3, so no other device may use that ID (p. 112). See Hard Drive Maintenance and Repair and Floppy Drive Repair.

Video card

Every 8100 needs a video card, AV card or PDS terminator in the processor-direct slot. To remove the card, push up the tab that holds it to the chassis and pull the card out gently. When refitting, do not force it; if it will not seat, take it out, check the logic board for damage and try again (SS pp. 74–76).

Logic board

Remove the top housing and the video card first (SS p. 77).

1. Disconnect the logic board power cable, the speaker, LED, CD-ROM/tape SCSI, floppy and CD-ROM audio cables from the top of the board, then the hard drive SCSI cable.
2. Remove the reset/interrupt actuator.
3. Remove the screw that secures the board. On the 8100/100 and 8100/110, move the wires of the thermoelectric cooler away from the centre hole before refitting this screw.
4. Slide the board forward until its slot lines up with the tab, lift the latch at the rear and pivot the front of the board out of the chassis.

Keep the RAM SIMMs and the 256K cache SIMM if the board is going away, but leave the ROM SIMM on it. Reconnect the LED cable when refitting (pp. 78–82). Do not unplug the thermoelectric cooler's red and black wires from the board (p. 17).

Memory

Eight megabytes are soldered to the board. Add 72-pin SIMMs of 80 ns or faster in pairs of the same size and speed, and use noncomposite SIMMs only; 264 MB is the maximum (SS pp. 6, 24). A mismatched pair makes About This Macintosh report the wrong amount of memory (p. 58), and a bad SIMM brings up a dialog box, not death chimes (p. 7). Apple's developer note gives the eight sockets as four pairs (Table A-1, p. 9).

The video card's VRAM goes from 2 MB to 4 MB with 512K VRAM SIMMs (SS p. 25).

Clock battery

The battery is on the logic board, so the board must come out to test or change it. Apple warns that the lithium battery can explode if handled or discarded improperly (SS pp. 94, 97).

1. Set a voltmeter to the 10 V DC range.
2. Hold the positive probe on the positive end of the battery (marked "+" on the logic board) and the negative probe on the negative end.
3. Replace the battery if it reads below 3.2 V (p. 95).

To change it, prise open the latch at the end of the holder with a small flat-blade screwdriver, lift off the cover and take the battery out; fit the new one the right way round (pp. 98–99). Apple's specification pages give the battery as 3.6 V lithium. A leaking lithium cell leaves acidic residue; neutralise it with bicarbonate of soda solution, rinse with isopropyl alcohol and check the nearby traces. See Battery Explosion, Capacitor or Corrosion Damage and Battery Refurbishment.

Logic board reset

Apple's first step for an 8100 that will not power up is a logic board reset (SS pp. 6, 100–104):

1. Unplug the computer and remove the top housing and the logic board.
2. Open the battery holder and take the battery out.
3. Check that the power supply cable is disconnected from the board and press the computer's power-on button.
4. Wait 5 to 10 minutes, refit the battery the right way round and reassemble.

The reset clears PRAM; set the date, time and other settings again afterwards. To clear PRAM without opening the case, hold Command-Option-P-R at startup before "Welcome to Macintosh" appears (p. 44).

Power supply

To remove the supply, take off the top housing, remove the chassis support brace, disconnect the logic board power cable, press the latch that holds the supply and slide it forward and out (SS pp. 83–87). The supply is automatically configured for 100–240 V and is rated at 200 W DC output (p. 35); the service parts are 661-1687 and 661-0232 (p. 130). Owners identify it as a Delta SMP-220DB, Apple 614-0012. Its connector pinout and owners' repairs are on Power Macintosh 8100 Troubleshooting; its capacitors are on Power Macintosh 8100 Capacitor Replacement Guide.

Cooling

Keep the vents clear. Apple's charts treat intermittent shutdowns first as thermal protection and allow 30 to 40 minutes for the computer to recover (SS p. 43).

Related pages

• Power Macintosh 8100
• Power Macintosh 8100 Troubleshooting
• Power Macintosh 8100 Capacitor Replacement Guide
• Apple Workgroup Server 8150
• Recommended Tools