Apple PowerBook Duo MiniDock Capacitor Replacement Guide

MiniDock logic board with the four electrolytics marked: red 330 µF 16 V, cyan 100 µF 35 V (photo jmacz, annotated by MacDat)

The Apple PowerBook Duo MiniDock logic board, 661-1664, carries four surface-mount aluminium electrolytic capacitors. MacDat describes all four as leaky and recommends replacing them even in a MiniDock that still works. Apple's Service Source covers the board only as an exchange part and gives no component values.

Signs of failure

• A fishy smell when the case is opened. jmacz smelled the capacitors on a MiniDock that still worked.
• Electrolyte residue around the capacitor pads. See Capacitor Failure Symptoms and Battery Explosion, Capacitor or Corrosion Damage for cleaning.
• Faults that Apple's charts trace to the logic board, such as no external video or a dead floppy port, on a MiniDock whose cables and peripherals test good.

Capacitor list

MiniDock logic board electrolytics (jmacz and MacDat, community sources)

Position	Capacitance	Voltage	Type	Size
C36	100 µF	35 V	Surface mount, 105 °C	10 mm diameter
C37	330 µF	16 V	Surface mount, 105 °C	10 mm diameter
C38	330 µF	16 V	Surface mount, 105 °C	10 mm diameter
C40	100 µF	35 V	Surface mount, 105 °C	10 mm diameter

MacDat gives the values, the count and the 10 mm size but no board positions; the designators and the 105 °C rating are from jmacz's post, read from his board. His list goes from C38 to C40 and does not say what is fitted at C39. The four sit in a row at one end of the board, beside the latch, as in the photograph, where the two 100 µF parts are next to each other. jmacz fitted polymer capacitors in place of all four.

Opening the MiniDock

Apple's take-apart order is top cover, mechanical latch, then logic board.

1. Shut down and disconnect the Duo and all cables.
2. Remove the three self-threading Torx T-6 screws that hold the top cover to the bottom cover.
3. Push the mechanical release lever in flush with the top cover. The covers will not separate with it open.
4. Separate the top and bottom covers until they come apart at the rear mounting tabs.
5. Remove the two T-6 screws holding the plastic faceplate to the latch and pull the faceplate straight off.
6. Remove the two T-6 screws holding the latch and the logic board to the bottom cover, pull the flex cable away and lift off the latch.
7. Raise the front of the logic board slightly and pull it out of the bottom cover. Unplug the modem interface card from J6 if fitted.

Warning: do not take the mounting clips off the posts at the ends of the latch. They hold the link, which is under spring pressure and can spring up and hit you.

Replacing the capacitors

1. Note the polarity marking on each capacitor before removing it.
2. Remove the old parts and clean the pads and the board around them of any electrolyte.
3. Fit new 105 °C parts of the same value and at least the same voltage, observing polarity.
4. Inspect the board for lifted pads and bridges before reassembly.

Reassembly

• When refitting the latch, put its two mounting tabs through the holes in the flex cable.
• Do not bend the metal grounding tabs on the bottom cover, and make sure the board snaps onto the two screw mounts.
• Never overtighten the self-threading screws. Before tightening each one, turn it back slightly until it drops into its existing thread.
• Check for broken plastic before closing the case; jmacz found a broken clip rattling inside his.

After the recap

Dock a Duo and check each port: external display, floppy drive, SCSI, ADB and both serial ports. Apple's symptom charts for the MiniDock are summarised on Apple PowerBook Duo MiniDock#Troubleshooting.

Related pages

• Apple PowerBook Duo MiniDock
• Apple PowerBook Duo Dock Capacitor Replacement Guide
• PowerBook Duo Capacitor Replacement Guide
• Recommended Tools