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

Macintosh Centris 660AV. Source: Wikimedia Commons.

**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

**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

**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

**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.

**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

**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

**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

**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

**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

**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 V 1/2AA lithium PRAM battery. These leak and can burst, spraying corrosive electrolyte across the logic board and destroying nearby components — 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.^[1]

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 — 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.^[2]

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.^[3]

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

↑ "Warning! Exploding Maxell PRAM Batteries", 68kMLA; and MacDat — Macintosh II family. Source for the leaking/exploding lithium PRAM battery that destroys nearby components.
↑ "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.
↑ "Compact/Desktop Power Supply Capacitor Lists (by make and model)", 68kMLA; and "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.

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.^[1]

PRAM battery

The Macintosh Centris 660AV backs up its clock and Parameter RAM from a 3.6 V ½AA lithium cell. These cells — red Maxell parts especially — 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 V cell.^[2]

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 — see Sad Mac Error Codes.

Related Pages

↑ Mac84, Macintosh LC series power-supply recapping guide; the 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.
↑ Warning! Exploding Maxell PRAM batteries, 68kMLA; and Mac Battery Leaks, MacDat. Source for the 3.6 V ½AA lithium PRAM cell, the Maxell leak/explosion board damage, and soft- versus hard-power PRAM retention.

[mac2_batt-1] "Warning! Exploding Maxell PRAM Batteries", 68kMLA; and MacDat — Macintosh II family. Source for the leaking/exploding lithium PRAM battery that destroys nearby components.

[quadra_tant-2] "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.

[mac2_psu-3] "Compact/Desktop Power Supply Capacitor Lists (by make and model)", 68kMLA; and "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.

[caps-4] Mac84, Macintosh LC series power-supply recapping guide; the 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.

[pram-5] Warning! Exploding Maxell PRAM batteries, 68kMLA; and Mac Battery Leaks, MacDat. Source for the 3.6 V ½AA lithium PRAM cell, the Maxell leak/explosion board damage, and soft- versus hard-power PRAM retention.

[1]

[2]

[3]

[1]

[2]