PowerBook 540 General Maintenance

PowerBook 550c motherboard (820-0709-A) with its 68040 processor daughterboard fitted; MacDat uses this photograph for the whole 500 series (photograph credited by MacDat to AEChadwick)

Care and preventive work for the PowerBook 500 series: the PowerBook 520, 520c, PowerBook 540 and 540c, which share one case, motherboard family, battery system and Service Source. Apple's own procedures come from the PowerBook 500 Series Service Source.

Before opening the machine

• Shut the computer down with the Shut Down command before taking out a battery. If you pull the battery while the machine is running, everything in RAM is lost.
• Disconnect the power adapter and remove both batteries or the PCMCIA module. Apple warns that the 500 series is very susceptible to static damage and tells technicians to wear an earthed wrist strap.
• All nine screw types are Torx. You need T-8 and T-6 drivers. The T-8 fits most of them, including the keyboard, hard drive, display and top case screws.
• Do not insert or remove the PCMCIA module with the computer on or asleep; the machine shuts down and the contents of RAM are lost.

Batteries

Main batteries

The 500 series uses the PowerBook Intelligent Battery, a 9.6 V, 1.9 Ah nickel-metal-hydride pack with its own processor that reports the charge to the Power Manager. Either bay takes a battery; the 520 and 520c were sold with one and the 540 and 540c with two.

Apple's test with a voltmeter on the 10 V DC range, probes on the battery terminals:

PowerBook 500 series battery voltages (Apple)

State	Voltage
Fully charged	About 10.8 V
Fully discharged	7.8 V
Stored out of the computer for a long time	May fall to 5.0 V

Apple's handling rules for these batteries:

• Do not leave a battery in the computer for more than a week without connecting the power adapter.
• Do not store a battery for more than six months without recharging it, and keep it somewhere cool and dark.
• With one battery, discharge it fully and recharge it once every 90 days. With two, swap the left and right batteries every month.
• Fully charge a replacement battery before using it.

The owner's manual adds that depleted batteries left in the computer for more than two weeks, especially somewhere hot, may be damaged so that they will not recharge, and warns that a damaged NiMH battery can leak potassium hydroxide, which burns skin and eyes.

The original packs date from 1994 and 1995, and owners report them leaking. One owner found that leakage from a 540c battery had eaten the plastic between its contacts. Remove the batteries from a machine going into storage and keep NiMH packs bagged, away from the computer. Clean any leakage from the contacts; see Battery Explosion, Capacitor or Corrosion Damage.

The cosmetic outer cover of each battery separates from the cell pack. Colin Wirth (This Does Not Compute) published a 3D-printable blank that carries the original cover, so an empty bay can be closed after a leaking pack is thrown away.

Running and charging from a modern supply

Apple's adapter delivers 16.4-16.6 V on two pins: VBATT, which charges the batteries, and VMAIN, which runs the computer. mmu_man, who designed an open-source USB-C adapter for the series, measured that on a 520c the VBATT pin is connected to the battery almost directly, with no current limit inside the computer, and the PowerBook disconnects it when it decides the battery is full. A bench supply feeding VBATT tripped its 1.3 A over-current limit while a battery charged. He reports that another owner has run a machine from 15 V on VMAIN for a year without trouble. A supply that feeds VBATT needs its own current limit.

Backup battery

A separate backup battery keeps the PRAM and the power management data while the computer is shut down and the main batteries are out. It is part 922-0786, under its own cover (922-0787) in the top case. The computer recharges it. Apple's check:

1. Set the date and time.
2. Shut the computer down.
3. Remove the main battery and disconnect the adapter for ten minutes.
4. Reconnect the adapter, refit the battery and switch on.
5. If the date and time have been lost, the backup battery is dead or discharged. Leave the PowerBook plugged in for 48 hours to recharge it; it can be used meanwhile.
6. If it still will not hold the time, replace it.

Reaching it means removing the battery or PCMCIA module, clutch covers, display access cover, display assembly, keyboard, hard drive, centre base cover, floppy drive and top case. Prise off the backup battery cover with a small flat-blade screwdriver, unplug the cable, lift it out of its cable guides and lift the battery out.

MacDat's list of laptops whose leaking NiMH backup packs damage boards names the PowerBook 150, 2400c and 3400c among Apple's machines, and not the 500 series. Inspect it anyway whenever the top case is off.

Prising out the backup battery cover (Service Source, PDF p. 129)

Power adapter

Apple's adapter test uses narrow probes, with the negative lead on the outer shield of the connector:

PowerBook 500 series adapter connector (Apple)

Pin	Signal	DC voltage
1	VBATT	16.4-16.6 V
2	VMAIN	16.4-16.6 V
3	GND	0 V
4	GND Sense	0 V

The 500-series adapter is not the one used by the PowerBook 140, 160 and 180, and Apple's manual says to use only the adapter supplied with the computer. Low End Mac gives the part numbers as M1893 or M1910. MacDat found leaking capacitors in two of these adapters and could not keep either working after a recap. The case is brittle and can only be opened by cracking the seam, which MacDat did in a vice with a pencil either side of the seam. The adapter's capacitor list is on PowerBook 540 Capacitor Replacement Guide.

Resetting the power manager

Apple's procedure, for a machine that will not power on with a good battery and adapter, or will not reset after a crash:

1. Remove the adapter and the batteries.
2. Leave the computer without power for 3-5 minutes.
3. Hold Control, Command, Option and the power key together for 5-10 seconds.
4. Refit the battery, reconnect the adapter if needed, and switch on.

Case, hinges and display

The plastics are brittle. Owners report the bottom of the display housing splitting where the rear cover meets the bezel, the panel between the display and the keyboard coming loose, and the dark clutch covers breaking when removed. Sean Malseed (Action Retro) describes the clips that hold the front display bezel as weak from new and says nearly all have broken; he published 3D-printed replacements, which he glued in place on his 540c.

To take off a clutch cover, Apple's method: with the battery or module out, open the display as far back as it goes, press in on both sides of the wide end of the right clutch cover to release its two front latches, rotate it up to release the third latch and lift it off; repeat on the left. When refitting the right cover, do not pinch or tear the display cable. When removing the whole display assembly, support it from beneath, disconnect the interconnect-to-logic-board cable, remove the two T-8 screws and slide the display left so the right clutch clears the cable loop.

Apple's normal behaviours for the passive-matrix 520 and 520c: a thin white line across the middle of the screen, and a display that dims or stops working below 5 °C or above 40 °C and recovers after warming up for half an hour. Polariser breakdown ("vinegar syndrome") and, on the greyscale 540, Hosiden "tunnel vision" are covered on PowerBook 540 Troubleshooting.

Keyboard and trackpad

To remove the keyboard: take out the battery or module, remove the middle two bottom housing screws with a T-8 driver, lift the front of the keyboard with a small flat blade and pull it forward, stand it upright, release the locking tabs on the two keyboard cable connectors, unplug them and lift it away. Apple's first cure for a cursor that sticks or jumps is to reset the power manager and clean the trackpad surface.

Storage

Hard disk

The internal drive is a 2.5-inch SCSI disk. Original drives suffer from stiction and from rubber bump stops that turn to goo; MacDat names Quantum and some Conner drives. Owners have replaced them with BlueSCSI and SCSI2SD PowerBook boards. To reach the drive, remove the battery and keyboard, then the T-8 mounting screw, and prise up the front of the drive. See Hard Drive Maintenance and Repair.

Floppy drive

For a disk that will not eject, Apple's chart starts with holding the trackpad button while switching on, then a straightened paper clip in the hole beside the slot. It names machines with serial numbers between FC410 and FC414, or between CD412 and CK414, as needing a new floppy drive. Badly fitted brackets also cause ejection faults. When fitting the brackets to a drive, start the screws, push the front of each bracket towards the top of the drive and hold it there while tightening. The floppy cable connector is not keyed and will go in upside down; note the folds and orientation before unplugging it, and fold the cable on top of the drive when refitting. See Floppy Drive Repair.

Memory card

The RAM card goes on the daughterboard under the daughterboard EMI shield, after the battery, keyboard and centre base cover are out. Handle it by the edges. The card and connector are keyed; forcing a card in the wrong way can damage the daughterboard. Press down only on the edge directly above the connector.

Capacitors

MacDat lists one surface-mount electrolytic on the motherboard, but its photograph of that board is of a 550c (silkscreen 820-0709-A), so check a 520 or 540 board before ordering. The other electrolytics are on the inverter board, on the passive-matrix and 540c display boards, and in the adapter. Values are on PowerBook 540 Capacitor Replacement Guide.

Preventive checklist

1. Take out the main batteries and check them and their contacts for leakage; measure them against Apple's figures.
2. Check the backup battery with Apple's date-and-time test.
3. Measure the adapter at pins 1 and 2 before connecting it.
4. Reset the power manager if the machine is unresponsive.
5. Open the case only with T-8 and T-6 Torx drivers, an earthed wrist strap and the batteries out, and take care with the clutch covers and bezel clips.
6. Replace the original hard disk before it fails, or image it while it still runs.

Related pages

• PowerBook 540
• PowerBook 520
• PowerBook 540 Troubleshooting
• PowerBook 540 Capacitor Replacement Guide
• PowerBook 500 Series Service Source
• Battery Refurbishment