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Power Macintosh G3 All-in-One General Maintenance

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Power Macintosh G3 All-In-One internal locator (Service Source)
Where the boards and drives sit (Service Source, PDF p. 21)

Routine work on the Power Macintosh G3 All-in-One: the chassis carrier, memory and cards, the processor module, the battery, the housing, and the power supply, analog board and fan in the upper case. The steps follow Apple's Service Source.[1] The logic board is the same as in the desktop and minitower;[2] Power Macintosh G3 (Beige) General Maintenance has more on it.

Safety

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The upper case holds a CRT and its high-voltage circuits. Apple's warning at the start of the CRT procedures is that the product contains high voltage and a high-vacuum picture tube.[1] Discharge the CRT before removing the power supply, analog/video board, fan, thermistor or CRT, as Apple's preliminary steps for each require, following CRT Discharge Procedure. The EMI shield over the CRT has sharp edges.[1]

The computer weighs 59.5 lb (27 kg).[3] Lift it with two people.

Chassis carrier

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The logic board, I/O card and drives come out of the back on the chassis carrier, which needs no other parts removed first.[1]

  1. Loosen the four screws and pull the carrier half way out.
  2. Unplug the front control panel cable, RGB cable, main power cable and hard drive power cable.
  3. Press up on the tabs to release the carrier and pull it out.

For memory and PCI cards alone, the developer note describes pulling the tray out until it stops, after removing the four captive screws.[2] Support the underside of the tray by hand while fitting PCI cards.[2] A 68kMLA member notes that bad contact is common in all-in-one Macs with a tray-mounted logic board, and that reseating the tray and its cards and cleaning contacts often cures odd behaviour.[4]

Memory and video memory

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  • Three slots take 168-pin 3.3 V unbuffered SDRAM DIMMs, up to 384 MB with three 128 MB DIMMs. DIMMs from older Macs fit but do not work.[1] DIMMs up to 1.5 in high fit in this case.[2]
  • The board has 2 MB of SGRAM soldered on and one slot for a 4 MB, 144-pin SGRAM SO-DIMM. Never fit the 256K or 512K video DIMMs from older Macs.[1]
  • Do not remove the ROM DIMM.[1]
  • To reach the slots, remove the chassis carrier and the cable clamp support bracket.[1]

PCI and I/O cards

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Remove the chassis carrier, then the screw and port access cover for the slot. If all three covers are removed, keep the sheet metal shield under the edge of the logic board.[1] The slots take 7-inch PCI cards: three cards, two 25 W cards, or one 15 W and one 25 W card.[1] The I/O card in the PERCH slot carries the sound and the video signal for the built-in display. The computer starts without it but does not work properly.[1][2] Clean residue off card connectors with a pencil eraser after checking them under a magnifier.[1]

Processor module and J16

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Remove the chassis carrier, I/O card and cable clamp support bracket. Then:[1]

  1. Remove the screw that holds the processor module wire to the logic board. Refit it with a hand screwdriver: there is a capacitor beside the screw hole.
  2. Press down on the heat sink clip and lift its front tab with a small flat-blade screwdriver; take off the clip and heat sink, which may be hot.
  3. Lift the metal lever at the left of the module and lift the module straight up by its edges.

The J16 jumper block beside the battery must match the module: red for 233 MHz, white for 266 MHz, fitted with the gold pins facing the board. A missing or wrong block gives a computer that does not start.[1]

Battery

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The PRAM battery is on the logic board next to the processor jumper block.[1] Apple specifies a 3.6 V lithium battery.[3] Remove old batteries: one owner who has bought many of these found battery damage on some boards.[5] See Battery Explosion, Capacitor or Corrosion Damage.

Housing

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Remove the chassis carrier and the front door first. The front door comes off by pulling down the bottom tab while prising the side slot with a screwdriver; its plastic tabs are fragile.[1]

  1. Remove the four screws on the CRT bezel that hold the housing.
  2. Remove the two plastic plugs over the top panel screws, and the two screws.
  3. Pull the housing back and lift it off. It comes off as one unit and separates into four panels (top 922-3476, rear 922-3475, left 922-3474, right 922-3473), held together by ten screws.

Power supply board

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Remove the chassis carrier, housing and CRT EMI shield (five screws), and discharge the CRT.[1]

  1. Push the tab in and lift the supply to clear the pegs from the chassis holes.
  2. Unplug the multicoloured power cable (P904), ground wire (P911) and the two-pin brown thermistor wire (TH901).
  3. Tilt the board aside and unplug P912 (thermistor cable), P905 (fan), P906 (grey ribbon to the I/O card, front panel and analog board), P913 (10-wire cable to the analog board and front panel) and P908 (5-wire cable to the analog board). P906 and P908 lock; squeeze to release them.
  4. When refitting, connect TH901, P908, P913, P906 and P905 before lowering the board, as some cannot be reached afterwards, and make sure the pegs seat in the chassis holes.

Analog/video board

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Remove the chassis carrier, housing and EMI shield, discharge the CRT and take off the anode cap. Unplug the microphone (P703), ground wire (P702), degaussing wire (P508) and yoke (P701), remove the CRT video board from the tube, lift the analog board out of the chassis holes, and unplug P502, P503, P505, P506 and P507 (all but P505 lock).[1] After replacing the analog board or CRT, Apple calls for the cutoff and white balance adjustments with its Display Adjustment Utility and Display Service Utility, with the display at 640 × 480 and warmed up for 10 minutes.[1]

Fan and thermistor

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The fan (922-3448) and its thermistor are reached after the power supply and analog board are out. Hold the fan while removing its two screws, as it drops when they come out.[1] Fan speed is controlled by temperature.[1]

Drives

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  • The hard drive, floppy drive, CD-ROM drive and optional Zip drive all come out with the chassis carrier.[1] Apple's Additional Procedures chapter covers adding a Zip drive to the expansion bay.[1]
  • A 68kMLA member finds the original IDE hard drives almost always need replacing.[4]
  • See Hard Drive Maintenance and Repair and Floppy Drive Repair.
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References

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  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 1.19 1.20 1.21 1.22 Apple Computer, Power Macintosh G3 All-In-One Service Source, hosted here as File:Power Macintosh G3 All-In-One Service Source.pdf (see Power Macintosh G3 All-In-One Service Source). PDF page numbers: features pp. 4-6; SDRAM pp. 16-17; SGRAM p. 18; DIMM slots p. 19; internal locator p. 21; logic board p. 24; Take Apart: chassis carrier pp. 43-46, hard drive pp. 47-49, floppy drive pp. 50-51, Zip drive pp. 52-54, CD-ROM pp. 55-58, I/O card pp. 59-62, cable support bracket pp. 63-65, logic board pp. 66-69, CRT EMI shield pp. 70-72, power supply pp. 73-78, analog/video board pp. 79-83, CRT bezel pp. 84-85, speakers pp. 86-87, front panel board pp. 88-89, CRT pp. 90-95, fan pp. 96-97, thermistor pp. 98-99, chassis with cables pp. 100-101, processor module pp. 102-111, front door pp. 112-113, housing pp. 114-118, tilt/swivel base pp. 119-120; Adjustments pp. 148-172; Upgrades pp. 173-179; Additional Procedures (adding a Zip drive) pp. 180-183; Exploded View pp. 184-187.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Apple Computer, Power Macintosh G3 Computers developer note (revised 8/13/98), hosted here as File:Power Macintosh G3 Computers Developer Note (1998).pdf (see Power Macintosh G3 Documentation). PDF p. 14: "The main logic board in all three enclosures" (All-in-one, desktop and minitower) has a mini-ATX form factor. Access to the logic board (PDF pp. 22-23): remove four screws and pull the logic board tray out until it stops; support the underside of the tray when installing PCI cards. DIMM height (PDF p. 34): 1.5 in maximum in the tower and all-in-one enclosures.
  3. ↑ 3.0 3.1 Apple, "Power Macintosh G3 All-In-One - Technical Specifications" (retrieved 2026-10-02). Weight 59.5 lb; battery type 3.6 V lithium; 32-384 MB in three DIMM slots, 10 ns.
  4. ↑ 4.0 4.1 68kMLA forum thread "G3 AIO Molar Macs wont start", September 2021. beachycove: reseat the logic board several times, since bad contact is common in any AIO with a tray logic board; reseat everything on the board; clean contacts with an eraser or high-concentration isopropyl alcohol; original IDE hard drives nearly always need replacing. Community repair report.
  5. ↑ 68kMLA forum thread "Power Macintosh G3 All In One (Molar Mac) Power Supply, Analog Board, And Deflection Board Recap List", November 2023 to November 2024. jajan547: every machine he bought needed work and some had battery damage, so pull the boards out; the AIO needs ADB soft power (the keyboard's power key) to start. Community repair report.


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