Troubleshooting the Macintosh Centris 660AV (also sold as the Quadra 660AV) requires understanding its unique architecture, including the AT&T DSP and GeoPort features. This guide covers the most common problems and their solutions.
Before detailed troubleshooting:
- Verify the power cable is firmly connected
- Check that the power outlet is working
- Ensure all cables (keyboard, mouse, monitor) are properly seated
- Remove any recently added RAM or expansion cards
- Reset PRAM (Cmd-Opt-P-R at startup, hold through three chimes)
- Reset CUDA (remove power and PRAM battery for 10 minutes)
Power Issues
| Symptom |
Possible Cause |
Recommended Action
|
| Dead, no LED |
Power supply failure |
Check power cable; test outlet; inspect PSU for dust buildup on filter mesh
|
| Dead, no LED |
PRAM battery dead |
Replace 3.6V half-AA lithium battery
|
| Ticking sound |
Power supply fault |
Check for shorts on logic board; inspect capacitors; test with known-good PSU
|
| Powers on briefly, then off |
Short circuit |
Remove all cards and RAM; test with minimal configuration
|
| Fan spins but no boot |
Logic board failure |
Check for capacitor leakage; inspect for corrosion
|
Video Problems
| Symptom |
Possible Cause |
Recommended Action
|
| Chime but no video |
PRAM battery dead |
Replace battery (common issue on 660AV/840AV per Apple KB TA35928)
|
| Chime but no video |
VRAM failure |
660AV VRAM is soldered; board repair or replacement required
|
| Chime but no video |
Monitor cable issue |
Test with different monitor and cable
|
| Garbled display |
VRAM failure |
Test with external video card if available
|
| No video to TV/VCR |
Video mirroring unsupported |
This is normal; 660AV does not mirror to TV (monitor goes blank during video output)
|
Tip: Hold Cmd-Opt-T-V during startup to force the Mac to use a TV as a monitor.
Chime Codes and Startup Issues
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Startup Sounds
| Sound |
Meaning |
Action
|
| Normal chime |
Hardware OK |
Issue is software or peripheral
|
| No chime |
RAM failure or no power |
Check power supply; reseat/test RAM
|
| Broken chime |
RAM failure |
Reseat or replace RAM SIMMs
|
| Series of tones |
Hardware diagnostic failure |
Count tones; refer to Apple service codes
|
Intermittent Booting or Freezing
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Stability Issues
| Symptom |
Possible Cause |
Recommended Action
|
| Random freezes |
Failing capacitors |
Inspect logic board for leakage; recap if needed
|
| Freezes after warmup |
Thermal issue |
Clean dust; check fan operation; reseat chips
|
| Freezes during disk access |
SCSI termination issue |
Verify internal drive is terminated; check SCSI ID conflicts
|
| Freezes with extensions |
Software conflict |
Boot with Extensions Off (hold Shift); isolate problem extension
|
The 660AV displays Sad Mac codes in the format XXXXXXXX / YYYYYYYY where the first number indicates the error class.
Common Sad Mac Codes
| First Digit(s) |
Error Type
|
| 01 |
ROM test failed
|
| 02 |
Memory test – bus sub-test failed
|
| 03 |
Memory test – byte write failed
|
| 04 |
Memory test – addressing failed
|
| 05 |
Memory test – pattern failed
|
| 0F |
Reserved for internal use
|
See Sad Mac Error Codes for a complete reference.
Audio Issues
| Symptom |
Possible Cause |
Recommended Action
|
| No sound |
Muted in Sound control panel |
Check volume setting
|
| No sound |
Capacitor failure |
Inspect and recap logic board
|
| Distorted sound |
Failing capacitors |
Recap logic board
|
| PlainTalk not working |
DSP issue |
Reinstall system software; check DSP chip
|
GeoPort and Modem Issues
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GeoPort Problems
| Symptom |
Possible Cause |
Recommended Action
|
| GeoPort adapter not recognized |
Driver issue |
Reinstall GeoPort software
|
| No dial tone |
Adapter not connected properly |
Check cable; try other GeoPort
|
| Poor modem performance |
DSP load |
Close other applications using DSP
|
Video Capture Problems
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Video I/O Issues
| Symptom |
Possible Cause |
Recommended Action
|
| No video input |
Wrong input selected |
Check Video control panel settings
|
| Grainy capture |
Poor signal |
Use S-Video instead of composite; check cables
|
| Dropped frames |
Slow hard drive |
Use faster SCSI drive; reduce capture resolution
|
| Audio/video sync issues |
Buffer settings |
Adjust capture software settings
|
Floppy Problems
| Symptom |
Possible Cause |
Recommended Action
|
| Cannot read disks |
Dirty heads |
Use cleaning disk; clean heads manually
|
| Disk eject failure (auto-inject) |
Mechanical wear |
Lubricate mechanism; replace drive
|
| Cannot write to disks |
Write protect tab |
Check disk; try different disk
|
| Disks not recognized |
Drive failure |
Replace floppy drive
|
See Macintosh Floppy Drive Maintenance for detailed drive service procedures.
SCSI Issues
| Symptom |
Possible Cause |
Recommended Action
|
| External device not found |
Termination issue |
Only terminate last device in chain
|
| Device conflict |
Duplicate SCSI ID |
Assign unique IDs (internal drive is usually 0)
|
| Slow performance |
Cable quality |
Use high-quality shielded cables
|
| Intermittent device |
Loose connection |
Check and reseat all SCSI cables
|
Software Compatibility
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- System 7.5–7.5.3: The Startup Disk control panel is incompatible with Quadra AVs. Upgrade to System 7.5.5.
- 24-bit addressing: Not supported. Ensure 32-bit mode is enabled.
- PowerPC upgrades: Require a "fat" (universal) system installation.
- Mac OS 8.1: Maximum supported version without PowerPC upgrade.
- Mac OS 9.1: Supported with PowerPC upgrade card installed.
