Macintosh Centris 610 General Maintenance

This page covers routine care for the Macintosh Centris 610 and the Macintosh Quadra 610, which share a logic board design, a case and a power supply and which Apple documents together.

Figures below come from Apple's Service Source for the Quadra 610 / Centris 610 / WS 60 and from Apple's Macintosh Centris 610, Macintosh Centris 650, and Macintosh Quadra 800 Computers Developer Note, both hosted on this wiki.

What this machine is

Apple's specification

Item	Centris 610	Quadra 610
Processor	Motorola 68LC040 at 20 MHz	68LC040 or 68040 at 25 MHz
FPU	None, and Apple offered no FPU upgrade for this product	Included with the 68040; absent on the 68LC040
RAM	4 or 8 MB standard, expandable to 68 MB, 80 ns or faster 72-pin SIMMs
ROM	1 MB
VRAM	512 K, expandable to 1 MB (80 ns or faster 68-pin SIMM)
PRAM	256 bytes of non-volatile parameter memory
Expansion	One internal slot taking a PDS card, or a 7-inch NuBus card with the adapter
Ethernet	Optional on-board	On-board
Line voltage	100–240 VAC, 50–60 Hz

All of that is Apple's. Two notes on reading it:

• Apple's printed specification table for the Centris 610 is mis-aligned. In the Memory section the labels have slipped by one row, so the manual appears to say "PRAM 1 MB", "VRAM 256 bytes of nonvolatile parameter memory" and "Clock/Calendar 512K, expandable to 1 MB". The intended reading — ROM 1 MB, PRAM 256 bytes, VRAM 512 K expandable to 1 MB, clock/calendar a CMOS chip with a long-life lithium battery — is the one given above, and it is what every other manual in the family prints.
• No FPU upgrade exists for the Centris 610. Apple prints that as a note in the specification, not as a footnote. Software demanding a floating-point unit will not run on a Centris 610, and that is not a fault to chase.

Power supply

The Centris 610 and the Centris 660AV share Apple service part 661-1688.

Apple's two documents disagree about this supply's rating, and the developer note is the one to believe. Apple's developer note says the power supply in the Centris 610 "uses a new design and provides 86 W total", and distinguishes it explicitly from the Centris 650's, which "delivers up to 112 W". The Service Source specification table for the Centris 610 prints 112 W — the 650's figure — in a table whose neighbouring rows are demonstrably shifted. The Centris 660AV, which takes the same 661-1688 supply, is given as 86 W in its own manual. Treat the Centris 610 supply as an 86 W unit.

A NuBus card in the Centris 610's single slot may use a maximum of 10 watts, allocated either as +12 V 2.1 W / −12 V 1.8 W / +5 V 6.1 W, or with the unused 12 V allowance rolled into +5 V for a full 10 W on that rail. That is a real design limit, and a card that exceeds it is a plausible cause of a machine that shuts down under load.

What Apple does and does not publish

Apple publishes no rail tolerance and no power-supply adjustment procedure for the Centris 610 or Quadra 610. The Service Source contains no acceptable-range table for any rail and no trimmer adjustment; every power fault in the symptom charts ends in "Replace power supply". The "+5 V 4.85–5.15 V / +12 V 11.9–12.7 V" table that circulates on pages of this era is Apple's Macintosh Plus procedure — genuine there, where it uses voltage test cable 077-0135 on the external floppy port — copied onto machines it was never written for. It has been removed from this page rather than reproduced, and no substitute has been invented.

What you can do instead is compare against a known load. Each rail at the logic-board power connector should sit close to its nominal value with the machine running and should not move when a drive spins up. A rail that is visibly low, or that sags under load, points at the supply. A rail that measures as a short to ground with the supply disconnected points at the logic board.

Recapping it

You are allowed to open this supply. Understand what is live in it first: it is mains-rectified, so with the cover off and the lead in, the fuse, input filter, bridge rectifier and reservoir capacitors sit at mains potential, and the reservoirs hold a charge after the plug comes out. Unplug, discharge each large reservoir through a 1 kΩ / 5 W resistor, and confirm with a meter that it reads near zero before a tool goes near the primary side.

If your unit has two reservoir capacitors in series across the rectified mains, replace both together with matched parts. That series pair is how a universal-input supply holds off 340 V of rectified 240 V mains on parts rated a couple of hundred volts each. A single capacitor in place of the pair will fail, violently, on European mains.

Battery

A 3.6 V lithium half-AA cell in a holder on the logic board keeps the real-time clock and parameter RAM alive with the machine unplugged.

Apple's check is a measurement, not a calendar. Set a meter to the 10 V DC range, put the positive probe on the positive end of the cell and the negative probe on the negative end, and replace the cell if it reads below 3.2 V. Apple publishes no replacement interval, and none is invented here: a cell above 3.2 V is doing its job and one below it should come out today whatever its age.

If it has leaked

This is a lithium cell, so neutralise with bicarbonate of soda, not vinegar. Vinegar is the right treatment for alkaline leakage, which is basic; it is the wrong treatment here and it adds water and chloride to an already corroded board. Use a paste of sodium bicarbonate and distilled water, rinse with distilled water, follow with isopropyl alcohol and dry thoroughly.

Then check the damage rather than assuming there is none:

• Inspect under magnification for traces that have gone dull, green or thin.
• Buzz out every track running away from the holder — corrosion travels under the solder mask and does not show from above.
• Check the underside of the board. Electrolyte wicks down through vias.

See Battery Explosion, Capacitor or Corrosion Damage and Battery Refurbishment.

Take the cell out before the machine goes into storage. That is not a service interval; it is the one measure that reliably prevents this damage.

Connectors and sockets

Oxidised contacts cause more intermittent faults on a machine this age than failed silicon does, and they are the cheapest thing to put right.

• SIMM sockets. Clean with isopropyl alcohol on a swab and reseat. Do not take an abrasive to a module's gold fingers — once you are through the plating, the base metal oxidises and then transfers to every socket the module touches.
• VRAM sockets. Same treatment. Video faults that come and go when the case is knocked usually start here.
• NuBus and PDS slots. Inspect for bent contacts and debris before a card goes home; check the card's edge fingers too.
• ROM SIMM socket, where one is fitted. A poorly seated ROM gives a machine that chimes and does nothing else.
• Logic-board power connector. Look for browning or a distorted housing. A discoloured power connector is a warning, not a cosmetic problem.
• ADB, serial, SCSI and floppy connectors. Reseat; check ribbon cables for cracked conductors where they fold.

A contact cleaner such as DeoxIT D5 earns its place on genuinely corroded contacts. It is not a preventive treatment and it does not belong on clean gold.

Capacitors

Ten 47 µF 16 V surface-mount electrolytics on the logic board — one value, one voltage, ten positions. MacDat records ten and notes that other sources say nine; its reference photograph shows ten. Designators, the annotated board photograph and the procedure are on Macintosh Centris 610 Capacitor Replacement Guide.

Apple published no capacitor values for this machine, so that figure is a community reading of physical boards rather than a manufacturer specification. Count the cans on your own board before ordering a kit.

What failure looks like: audio goes first, then intermittent starting, then visible residue. A surface-mount electrolytic does not have to look swollen to have failed — the usual failure is a seeped seal, and the evidence hides under the can. See Capacitor Failure Symptoms.

Cleaning

Opening the case

Disconnect everything, press the release tabs at the rear and lift the cover off. There are no tools involved and no hidden screws.

Inside

• Compressed air and an anti-static brush on the logic board, the supply and the fan. Hold the fan blade still while you blow it: spinning a fan with compressed air drives it as a generator and puts a reverse voltage back down its cable.
• Isopropyl alcohol (99 %) and a soft brush for grime, working outwards from each capacitor and from the battery holder.
• Check the underside of the board as well as the top. Both battery and capacitor electrolyte travel through vias.

Outside

• A damp microfibre cloth and mild detergent. No abrasives, no solvents — the texture on these shells does not survive either.
• ADB keyboards come apart for washing: keycaps off, warm soapy water, dry them completely, then clean the contacts with isopropyl alcohol.
• Mouse ball out, rollers scraped and wiped with isopropyl alcohol.

The platinum-grey plastics yellow with age. The discolouration is in the body of the plastic rather than on the surface, so cleaning will not shift it; see Retrobrite for what can be done and what it costs in brittleness.

Floppy drive

The 1.4 MB Apple SuperDrive is direct drive. It has no belt. Advice to fit a new belt to a sluggish or non-ejecting SuperDrive — including to the auto-inject version — is wrong: there is nothing there to replace. What these drives actually suffer is hardened grease on the head carriage and eject rails, dust in the mechanism, and dirty or worn heads. On manual-inject drives a worn eject gear is a genuine and common failure.

• Clean the heads with isopropyl alcohol on a lint-free swab, supporting the upper head arm so it is not sprung.
• If the rails are stiff, re-lubricate with a silicone grease — not white lithium grease, which gums up as it ages.
• If a disc will not eject, hold the mouse button down while switching the machine on to run a full eject cycle before taking anything apart.

See Macintosh Floppy Drive Maintenance.

Hard disk

The original SCSI mechanisms are past thirty years old and the usual failures are a stuck spindle, dried head-park grease and dead controller electronics. Solid-state replacements — BlueSCSI, ZuluSCSI, SCSI2SD — are quieter, cooler and considerably more reliable, and they let you keep the original drive on a shelf.

Whatever you fit, get the termination right: the drive at the end of the internal bus must be terminated, and the computer itself is always SCSI ID 7. See Macintosh HDD Maintenance.

Storage

• Take the battery out.
• Store dry and at room temperature — not a loft, not a garage.
• If the logic board comes out, bag it anti-statically and lay it flat.
• Nothing needs periodic running. "Power it up every few months to keep the capacitors formed" is repeated widely and supported nowhere for machines of this kind. The real hazard to a stored Macintosh is the cell in the battery holder, and removing it costs nothing.

Related pages

• Macintosh Centris 610
• Macintosh Centris 610 Capacitor Replacement Guide
• Macintosh Centris 610 Troubleshooting
• Macintosh Quadra 610
• Macintosh Quadra 610/ Centris 610/WS 60 Service Source
• Macintosh Centris 610 Centris 650 and Quadra 800 Developer Note
• Recommended Tools