Editing Macintosh Centris 660AV Troubleshooting

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.

== Preliminary Checks ==

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)

== No Power ==

<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''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
|}

== No Video ==

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''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 ==

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''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 ==

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''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
|}

== Sad Mac Error Codes ==

The 660AV displays Sad Mac codes in the format XXXXXXXX / YYYYYYYY where the first number indicates the error class.

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''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 Problems ==

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''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 ==

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''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 ==

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''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 Drive Issues ==

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''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 Problems ==

{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+ '''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 ==

* '''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.

== Related Pages ==

* [[Macintosh Centris 660AV]]
* [[Macintosh Centris 660AV General Maintenance]]
* [[Macintosh Centris 660AV Capacitor Replacement Guide]]
* [[Sad Mac Error Codes]]
* [[Macintosh Floppy Drive Maintenance]]

[[Category:Apple Vintage Computers]]
[[Category:Apple Troubleshooting Guides]]