Macintosh Centris 660AV Troubleshooting

Macintosh Centris 660AV (Wikimedia Commons, CC BY-SA 3.0)

Symptom-based troubleshooting for the Macintosh Centris 660AV, sold from October 1993 as the Macintosh Quadra 660AV. The tables follow Apple's symptom charts, which list cures in order of likelihood: try the first, check whether the symptom persists, and if a replaced module did not cure it, refit the original before trying the next. Apple's charts work at module level; on a board of this age "replace logic board" often means leaking capacitors or battery damage, covered at the end.

Preliminary checks

• Mains lead connected and outlet working; monitor powered (Apple's first no-power step is to plug the monitor straight into the wall and check it has power).
• Keyboard, mouse and monitor cables seated.
• Third-party RAM and cards removed, which is an early step in Apple's no-power chart.
• PRAM battery present and reading at least 3.2 V (see Battery).

System and power

Apple's system and error-chord charts

Symptom	Apple's cures, in order
Does not power on; screen black, fan not running, LED not lit	Check cables; plug the monitor directly into the wall and check it has power; remove third-party RAM and cards; replace power cord; replace power supply; replace logic board
Clicking, chirping or thumping	Replace power supply; replace logic board
Shuts down intermittently	Check the air vents are clear (thermal protection may shut the system down; it should be usable again after 30 to 40 minutes); replace power cord; check the battery; replace power supply; replace logic board
Crashes or locks up intermittently	Check the system software version; disconnect external SCSI devices; try known-good application software; replace SIMMs; replace logic board; replace power supply
One-part error chord during start-up	Disconnect the SCSI data cable and hard drive power cable and restart; if start-up is then normal, test and if necessary replace the hard drive. Disconnect the floppy drive cable and restart; if start-up is then normal, replace the floppy drive. Otherwise replace the logic board
Two-part error chord during start-up	Replace the DRAM SIMMs; replace the logic board, then check the DRAM SIMMs on the replacement board

The supply is Apple service part 661-1688, shared with the Centris 610. Low End Mac notes that the fan filter for this case is inside the power supply, and that clearing dust from the mesh screen near the fan can revive a supply that appears to have failed. Before opening the supply, read the mains and stored-charge warning on Macintosh Centris 660AV Capacitor Replacement Guide. Apple publishes no rail tolerances for this machine.

Video

Apple's video chart

Symptom	Apple's cures, in order
Screen black; sound and at least one drive work; fan running, LED lit	Adjust the monitor brightness; check cables; check the monitor is switched on; clear PRAM (Command-Option-P-R at start-up); replace video cable; try another monitor; replace video card, if fitted; replace SIMMs; replace logic board; replace power supply
Screen black; no sound and no drive activity; fan running, LED lit	Remove peripherals and cards; remove the expansion card; replace DRAM SIMMs; replace power supply; replace logic board
Part or all of the screen bright with sound present, but no picture	Try another monitor; replace video cable; replace video card, if fitted; clear PRAM; replace logic board

Before working through the black-screen rows, measure the PRAM battery: a flat or low battery can stop the built-in video on this model (see Battery).

Things that are not faults: video memory is 1 MB soldered and cannot be expanded, and the computer's monitor goes blank while video is sent to a television or VCR, because the AV machines do not mirror video. Holding Command-Option-T-V at start-up forces the machine to use a television as its monitor.

Sad Mac

A Sad Mac icon with two lines of hexadecimal code is decoded on Sad Mac Error Codes and with the Sad Mac Decoder. The first line's last two digits give the failing test (for example 01 is the ROM checksum, 04 and 05 are RAM tests and 0F an exception), and the second line identifies the failing bit, address or exception.

Floppy drive

Apple's floppy drive chart

Symptom	Apple's cures, in order
Sound and picture present, but the internal floppy drive does not work	Try a known-good disk; disconnect all external SCSI devices; replace floppy drive cable; replace floppy drive; replace logic board; replace power supply
Disk ejects and the screen shows an icon with a flashing X	Try a known-good system disk; replace floppy drive cable; replace floppy drive; replace logic board
Disk does not eject	Switch off, then hold the mouse button down while switching on; replace floppy drive cable; replace floppy drive; replace logic board
Drive tries to eject but the disk does not come out	Push the disk fully in; reseat the floppy drive bezel and drive so the bezel slot lines up with the drive; eject manually; replace floppy drive
Internal floppy drive runs continuously	Try a known-good system disk; remove external SCSI devices; replace floppy drive cable; replace floppy drive; replace logic board
An MS-DOS drive will not read a disk formatted on the 1.4 MB drive	Format disks in the MS-DOS drive first; check the software is loaded

See Macintosh Floppy Drive Maintenance for head cleaning.

Hard drive, CD-ROM and SCSI

Apple's hard drive and CD-ROM charts

Symptom	Apple's cures, in order
Internal hard drive does not work and does not spin	Replace SCSI data cable; replace hard drive; replace power supply; replace logic board
Drive does not appear on the desktop	Check for duplicate SCSI IDs; clear PRAM; check the drive is initialised (HD SC Setup); replace SCSI data cable; replace hard drive
Works with internal or external SCSI devices but not both	Check for duplicate SCSI IDs; replace the external device's terminator; replace external SCSI cables; check the external device
CD-ROM drive does not accept a disc	Try another disc; check the CD-ROM carrier is fitted properly; replace CD-ROM mechanism
No CD-ROM icon on the desktop	Check the CD-ROM extension is in the System Folder; replace SCSI data cable; replace CD-ROM mechanism; replace logic board
Disc will not eject	Eject manually; press the eject button behind the front bezel, if accessible; replace CD-ROM mechanism

The computer is always SCSI device 7, and up to six external devices are supported. The developer note says the internal and external SCSI buses are terminated automatically when no devices are connected.

Keyboard and mouse

Apple's peripheral chart

Symptom	Apple's cures, in order
Cursor does not move	Check the mouse connection; clean the inside of the mouse; if the mouse is plugged into the keyboard, plug it into the computer's ADB port, and if it then works replace the keyboard or ADB cable; if it fails in every port replace the mouse; replace logic board
Cursor moves but clicking does nothing	Replace mouse; replace logic board
Double-click does not open anything	Remove duplicate System files; clear PRAM; check the mouse as above; replace logic board
No response to any key	Check the keyboard connection; replace keyboard cable; replace keyboard; replace logic board

Software

Low End Mac lists these for the AV Quadras:

• The Startup Disk control panel in System 7.5 to 7.5.3 is incompatible with them; System 7.5.5 fixes this.
• They do not support 24-bit addressing.
• A PowerPC upgrade needs a "fat" (68K and PowerPC) system installed.
• The highest system supported without a PowerPC upgrade is Mac OS 8.1.

Speech recognition, audio compression and analog modem functions run on the AT&T DSP3210. If those fail while the machine otherwise runs, check that the AV system software is installed before suspecting hardware.

Battery

The clock and PRAM run from a 3.6 V lithium battery. Low End Mac notes that a dead or low battery can temporarily stop the built-in video on this model, citing Apple's article "Macintosh Computers: Low Battery Can Cause No Video". Apple's test is to measure the battery on the 10 V DC range and replace it below 3.2 V; Apple warns that the lithium battery can explode if handled or disposed of improperly. A machine found dead after storage should be checked for battery leakage around the holder before anything else; lithium leakage is cleaned with bicarbonate, not vinegar. See Battery Explosion, Capacitor or Corrosion Damage.

Logic board capacitors

The logic board carries thirteen surface-mount aluminium electrolytics (eleven 47 µF 16 V and two 10 µF 16 V, per Recap-a-Mac's map). Electrolytics of this age leak a corrosive electrolyte that eats through traces and pads. Look for residue or corrosion around them when sound, start-up or video faults do not follow Apple's charts. See Capacitor Failure Symptoms and Macintosh Centris 660AV Capacitor Replacement Guide.

Related pages

• Macintosh Centris 660AV
• Macintosh Centris 660AV General Maintenance
• Macintosh Centris 660AV Capacitor Replacement Guide
• Sad Mac Error Codes
• Macintosh Floppy Drive Maintenance