Macintosh Centris 660AV Capacitor Replacement Guide

This guide covers capacitor replacement on the Macintosh Centris 660AV, sold after Apple's 1993 renaming as the Quadra 660AV. The two are the same machine and Apple services them in one manual.

Unlike its desktop sibling the Macintosh Centris 650, this machine's logic board does carry surface-mount aluminium electrolytic capacitors, and they leak. This is the single most important repair fact about the AV machines of this generation.

What Actually Fails

The 660AV logic board carries thirteen surface-mount aluminium electrolytic capacitors. After thirty years the electrolyte creeps out under the can, wicks along the solder mask and eats through the copper. The board is a dense, fine-pitch design and the traces under and around the capacitors are thin, so corrosion breaks connections before it becomes visually obvious.

Symptoms that point at leaked electrolyte rather than anything else:

• Audio faults first. Distorted, crackling, one-sided or missing sound is usually the earliest sign, because several of the electrolytics sit in the audio section and the surrounding traces are among the first to corrode.
• Intermittent or absent start-up chime while the fan and drives run normally.
• Faults that change when the board is flexed or warmed. Corroded traces make intermittent joints.
• Visible residue — a dark, slightly glossy halo around a can, or a crusty white-green deposit on nearby pads. Wipe with isopropyl alcohol and look at the pads under magnification; a leaking cap often looks perfect from above.

Apple's own symptom chart for this machine routes clicking, chirping or thumping noises and dead-on-arrival units to the power supply, and routes two-part error chords at start-up to the DRAM SIMMs and then the logic board. None of that catches electrolyte damage, because Apple serviced these at module level and never expected anyone to repair a board.

Apple published no capacitor values for this machine. The Service Source contains no capacitance, working-voltage or component-designator data anywhere. Everything below is community data from a named source, and you should read the markings on your own board before ordering parts.

Logic Board Capacitors

Recap-a-Mac's annotated board map, produced from a physical Quadra 660AV logic board, gives the complete count:

Quadra / Centris 660AV logic board — surface-mount electrolytics

Quantity	Capacitance	Voltage
11	47 µF	16 V
2	10 µF	16 V

Thirteen parts, two values. There are no 1 µF positions and no 50 V positions on this board. The positions are not laid out in a numbered run — use the annotated map rather than hunting for designators.

Suggested replacements

Recap-a-Mac fits solid tantalum parts in these positions, which removes the leakage failure mode permanently:

• 47 µF 16 V — Kemet T491D476K016AT
• 10 µF 16 V — Kemet T491B106K016AT

Both are 16 V parts sitting on a 5 V rail, which satisfies the usual 50 % derating rule for solid tantalums comfortably. If you substitute, keep that rule in mind: a solid tantalum on a 5 V rail wants at least 10 V, and one on 12 V wants 25 V. Tantalums fail short rather than open, so under-rating one turns a leaky capacitor into a dead short across a supply rail.

Polymer aluminium or polymer tantalum parts are the other sensible choice: same footprint, no leakage, and a benign failure mode. Fresh aluminium SMD electrolytics will work but will eventually do the same thing again.

Note the polarity convention changes if you switch types. On an aluminium electrolytic the stripe marks the negative terminal; on a tantalum the bar marks the positive terminal. Fitting a tantalum "the same way round" as the part you removed will destroy it.

Capacitor Location Diagram

Quadra 660AV capacitor location map (Recap-a-Mac)

Quadra 660AV logic board, showing the surface-mount capacitor positions (Recap-a-Mac)

Replacement Procedure

1. Prepare — ESD mat and strap, good light, magnification.
2. Remove the logic board and work on it out of the case.
3. Photograph the board before touching anything, including close-ups of each capacitor's orientation.
4. Remove the old capacitors. Hot air at around 300 °C, or twist them off with pliers and clean up the pads afterwards. Do not lever them off cold — the pads lift.
5. Clean thoroughly. Scrub the area with isopropyl alcohol and a stiff brush, then inspect the pads and the surrounding traces under magnification. Electrolyte left in place carries on corroding.
6. Check continuity on every trace running out of the capacitor areas before fitting new parts. A broken trace found now is five minutes' work; found later it is a fault hunt.
7. Fit the new capacitors, correct way round for the type you are using. Tin one pad, tack one end, solder the other, then reflow the first.
8. Clean off the flux and inspect every joint.
9. Test with the board out of the case — power, video, keyboard — before reassembling.

If leakage has already broken traces, see Battery Explosion, Capacitor or Corrosion Damage for repair technique, and Capacitor Failure Symptoms for what failure looks like elsewhere in the machine. See Recommended Tools for the kit this wiki recommends.

Power Supply

The 660AV's internal supply is a mains-rectified switching supply. Its primary side sits at mains potential and the reservoir capacitors hold a lethal charge after the machine is unplugged. Recapping it is a reasonable job, but discharge each large capacitor through a 1 kΩ / 5 W resistor and confirm with a meter before touching anything, work one-handed where you can, and do not probe a powered primary side without an isolation transformer.

No verified component-level capacitor list exists for this supply. Apple published none, Recap-a-Mac's guide covers the logic board only, and no community list for the 660AV supply could be found. Open yours, read the markings off the parts and work from those. If you produce a list, it is worth posting.

Apple's electrical specification for the machine is 100–240 V AC, 50–60 Hz, 86 W. The supply is self-configuring, so there is no voltage selector to set wrongly.

Battery

Apple's documented check: set a voltmeter to the 10 V DC range, measure across the cell, and replace it if it reads below 3.2 V.

A leaking cell attacks the board in exactly the same way leaking capacitors do, and on this board the two kinds of damage often overlap. Check it every time the machine is open.

Related Pages

• Macintosh Centris 660AV
• Macintosh Centris 660AV General Maintenance
• Macintosh Centris 660AV Troubleshooting
• Macintosh Quadra 840AV Capacitor Replacement Guide — the same electrolyte problem, worse
• Capacitor Failure Symptoms
• Recommended Tools