Power Macintosh 7100 General Maintenance

Apple's logic board connector diagram for the 7100: SIMM sockets, 601 PDS, L2 cache slot, 4 MB ROM and soldered DRAM (Service Source p. 18)

Apple's Power Macintosh 7100 Series Service Source gives the take-apart order, battery test, logic board reset and memory rules for the Power Macintosh 7100 (7100/66, 7100/66AV, 7100/80 and 7100/80AV). The manual is module-level and gives no component values or rail voltages. Diagnosis by symptom is on Power Macintosh 7100 Troubleshooting, and the logic board capacitors on Power Macintosh 7100 Capacitor Replacement Guide.

Before you start

• Unplug the mains lead. The power supply (661-0758) is auto-ranging, 100–240 V (p. 31), and is replaced as a module in Apple's scheme; its primary side carries mains voltage and its input capacitor can stay charged after unplugging.
• Ground yourself and work on an anti-static mat; each take-apart procedure opens with Apple's ESD caution.
• The battery is lithium. Apple warns that "if handled or discarded improperly, the lithium battery in the computer could explode" (p. 119).

Take-apart order

Apple's procedures, in the order the modules come out (pp. 53–88):

1. Top housing: loosen the captive screw at the rear without forcing it, slide the housing forward about an inch and lift it straight up. Do not tilt it. On refitting, check the EMI gaskets inside the bottom edges and do not knock the reset/interrupt switch and light pipe out of line.
2. Power supply: if a CD-ROM drive is fitted, squeeze its side tabs and pull it out an inch or two. Remove the power supply strap if there is one (it is part of the shipping packing on some supplies and should be refitted), take out the screw at the rear panel, pry the latch away from the base of the supply and lift it out firmly. The lift unplugs the supply from the logic board.
3. Drive chassis: disconnect the floppy cable and the SCSI power and data cables (and the CD-ROM audio cable), remove the two chassis screws, swing the front of the chassis up until it is vertical, and lift its tabs out of the slots in the bottom housing.
4. Video card: pull up evenly on both ends so the connector pins do not bend.
5. Logic board: remove the reset/interrupt actuator and, if necessary, the speaker. Take out the customer's SIMMs and cache SIMM first. The ROM and cache SIMM sockets are interchangeable, so make sure the module you remove is the cache (five chips a side), not the ROM. Remove the centre screw, slide the board about half an inch towards the front and lift it out.

Clock battery

The battery is a lithium cell in a holder with a latched cover on the logic board; Apple's specification pages give it as 3.6 V lithium. To test it (pp. 119–120):

1. Remove the top housing, power supply and drive chassis.
2. Set the meter to the 10 V DC range.
3. Put the positive probe on the positive end of the battery (marked "+" on the logic board) and the negative probe on the other end.
4. Replace the battery if it reads below 3.2 V.

To replace it, pry open the latch at the end of the holder with a small flat-blade screwdriver, lift off the cover and take out the cell (pp. 121–123). Fit the new one the right way round. Low End Mac gives the cell as a 3.6 V half-AA. Cells of that type are lithium-thionyl-chloride and leave acidic residue when they leak; clean it off and neutralise with bicarbonate of soda, as described on Battery Explosion, Capacitor or Corrosion Damage.

Logic board reset

Apple's first cure for a machine that will not power up is to reset the logic board before replacing anything (pp. 6, 124–128):

1. Remove the top housing, power supply and drive chassis, and unplug the power cord.
2. Open the battery holder and take out the battery.
3. Press the power-on button on the rear panel, beneath the power socket.
4. Wait 5 to 10 minutes, then refit the battery (check its polarity), the drive chassis and the power supply.

The reset clears PRAM, so check the date, time and other settings afterwards.

Memory, cache and video

• Install SIMMs in matched pairs of the same size and speed: 72-pin, noncomposite, 80 ns or faster. The 16 MB configuration has two 4 MB SIMMs on top of the 8 MB soldered (p. 21).
• Bad SIMMs produce a dialog box at start-up, not the death chimes of 680x0 Macs (p. 7).
• The cache SIMM is a 256K module with five chips on each side (p. 86).
• The 7100/66 and 7100/80 must have the 2 MB Video Card in the PDS, the AV models the AV Card. A machine without one may not boot or may crash (pp. 8, 90, 111). The Video Card's VRAM goes to 2 MB with four 256K VRAM SIMMs (p. 22).

Source: service manual.

Fan and ventilation

The 7100/80 and 7100/80AV have a fan clipped under the metal drive chassis by five plastic tabs, next to the DRAM heat sink. Take care not to knock the heat sink or the DRAM chips when removing or refitting it, and check the new fan runs before the top housing goes back on (pp. 78–82). Keep the vents clear: Apple's chart for intermittent shutdowns says thermal protection may shut the machine down and that it recovers after 30 to 40 minutes (p. 39).

Drives and SCSI

• The internal hard drive is terminated and the internal CD-ROM drive is not (p. 48).
• The external SCSI port takes up to six devices, five with an internal CD-ROM drive (p. 25).
• The SCSI data cable connectors are keyed; you may need to twist the cable to fit them (p. 75).

Source: service manual. See Hard Drive Maintenance and Repair and Floppy Drive Repair. Low End Mac notes that the floppy sled is shared with the IIvi, IIvx, Centris 650 and Quadra 650.

Related pages

• Power Macintosh 7100
• Power Macintosh 7100 Troubleshooting
• Power Macintosh 7100 Capacitor Replacement Guide
• Power Macintosh 7100 Series Service Source
• Recommended Tools