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" />
[[File:Macintosh Centris 660AV (photo).jpg|thumb|right|300px|Macintosh Centris 660AV. Source: Wikimedia Commons.]]
{| 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.

== ⚠️ PRAM battery — remove it now ==

The Centris 660AV carries a 3.6&nbsp;V 1/2AA lithium PRAM battery. These leak and can '''burst''', spraying corrosive electrolyte across the logic board and destroying nearby components &mdash; often while the machine simply sits in storage. '''Remove the PRAM battery from any un-serviced unit.''' If one has leaked, neutralise and clean the residue and repair corroded traces and vias before troubleshooting.<ref name="mac2_batt">[https://68kmla.org/bb/threads/warning-exploding-maxell-pram-batteries.25169/ "Warning! Exploding Maxell PRAM Batteries"], 68kMLA; and [https://macdat.net/macintosh/macii/macintosh_iicx.html MacDat &mdash; Macintosh II family]. Source for the leaking/exploding lithium PRAM battery that destroys nearby components.</ref>

== Logic board (tantalum capacitors) ==

Unlike the LC and Mac II surface-mount-electrolytic boards, the 68040-family Centris 660AV logic board uses '''tantalum''' capacitors, which do not leak with age &mdash; the '''logic board does not normally need recapping'''. If the board misbehaves, look to leaked-PRAM-battery corrosion, socket/connector contacts and the power supply rather than to board capacitors.<ref name="quadra_tant">[https://retroviator.com/2021/09/02/apple-macintosh-quadra-650/ "Apple Macintosh Quadra 650"], Retro Viator; and the Apple Macintosh Quadra/Centris 650 Service Source. Source for the 68040-family logic boards using tantalum capacitors (no logic-board recap needed) while the power supply uses electrolytics that do need replacing.</ref>

== Power supply ==

The power supply uses electrolytic capacitors that fail with age (fails to power on, unexpected power-off, clicking when plugged in). '''Recap the power supply''' and confirm the rails.<ref name="mac2_psu">[https://68kmla.org/bb/threads/compact-desktop-power-supply-capacitor-lists-by-make-and-model.35890/ "Compact/Desktop Power Supply Capacitor Lists (by make and model)"], 68kMLA; and [https://www.bigmessowires.com/2016/04/21/capacitor-replacement-in-a-vintage-power-supply/ "Capacitor Replacement in a Vintage Power Supply"], Big Mess o' Wires. Source for the shared desktop PSU form factor (IIci/IIcx/IIvi/IIvx/Performa 600/Quadra 650/Quadra 700), the electrolytic failure symptoms and the PSU capacitor lists.</ref>

== AV features ==

The Centris 660AV adds the AT&T DSP3210 digital signal processor and video in/out. If the machine boots but AV functions (video capture/out, enhanced sound) fail, confirm the AV software/extensions are installed and check the DSP and the AV connector before suspecting the main logic.

== References ==

<references />

== Component-level faults (deep dive) ==

=== Surface-mount capacitor leakage ===

The Macintosh Centris 660AV logic board uses surface-mount electrolytic capacitors whose electrolyte turns corrosive with age and creeps across the board, eating through traces, pads and IC pins. Typical signatures are a machine that will not chime, chimes but shows no video, plays distorted or missing audio, or shows a garbled or checkerboard screen. Wash the affected area and replace every electrolytic with a tantalum or polymer part, then repair any lifted traces. The switch-mode power supply (ASTEC or TDK on the LC-family machines) holds its own electrolytics and fails the same way, so recap it alongside the board.<ref name="caps">Mac84, [https://mac84.net/web/macintosh-lc-series-lc-lc-ii-lc-iii-power-supply-recapping-guide-astec-usa/ Macintosh LC series power-supply recapping guide]; the [http://www.maccaps.com/MacCaps/Capacitor_Reference/Capacitor_Reference.html MacCaps capacitor reference]; and iFixit. Source for surface-mount electrolytic leakage eating traces, pads and pins, the ASTEC/TDK LC power-supply cap failures, and Apple's use of tantalum (non-leaking) capacitors on the Quadra 700/900 logic boards.</ref>

=== PRAM battery ===

The Macintosh Centris 660AV backs up its clock and Parameter RAM from a 3.6&nbsp;V &frac12;AA lithium cell. These cells &mdash; red Maxell parts especially &mdash; leak or burst and corrode the board, so remove an aged one on sight. A flat cell can also stop a soft-power machine booting or disturb the video; left plugged in, trickle power preserves the settings, but a machine switched off at the wall with a dead cell loses them. Clean the area and fit a fresh 3.6&nbsp;V cell.<ref name="pram">[https://68kmla.org/bb/threads/warning-exploding-maxell-pram-batteries.25169/ Warning! Exploding Maxell PRAM batteries], 68kMLA; and [https://www.macdat.net/repair/kb/batteries_macintosh.html Mac Battery Leaks], MacDat. Source for the 3.6&nbsp;V &frac12;AA lithium PRAM cell, the Maxell leak/explosion board damage, and soft- versus hard-power PRAM retention.</ref>

=== Boot chime and Sad Mac ===

Read the start-up sound first: a normal chime with a black screen points to the display path or the monitor, an absent chime or a "chord of death" points to RAM or a core fault, and a Sad Mac shows a numeric code &mdash; see [[Sad Mac Error Codes]].

== 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]]