Macintosh Quadra 605 Troubleshooting

Troubleshooting is essential for diagnosing and resolving issues with your Macintosh Quadra 605. This guide also applies to the LC 475, Performa 475, and Performa 476, which share the same logic board.

Preliminary Checks

Before detailed troubleshooting:

Verify the power cable is securely connected and the outlet works.
Check that the keyboard and mouse are connected to the ADB port.
Disconnect all external SCSI devices to rule out SCSI chain issues.
Remove any third-party RAM or expansion cards to test with stock configuration.

No Power

**No Power Issues**
Symptom	Possible Cause	Recommended Action
Completely dead, no LED	Faulty power cable	Test with known-good cable
Completely dead	Failed power supply	Test PSU output voltages; recap if capacitors have failed
Completely dead	Shorted logic board	Inspect for visible damage, burnt components, or electrolyte from leaked capacitors
Clicking or ticking sound	Power supply capacitor failure	Recap the power supply
Intermittent power	Loose power connector	Reseat logic board power connector; check for corrosion

Power Supply Testing

The Quadra 605 uses the LC-series power supply. Test voltage outputs:

+5V rail: Should read 4.85V – 5.25V
+12V rail: Should read 11.4V – 12.6V

If voltages are out of spec or absent, the power supply requires recapping or replacement.

Chime but No Video

**Video Issues**
Symptom	Possible Cause	Recommended Action
Chime, no video, drive activity	Failed VRAM	Reseat or replace VRAM SIMMs
Chime, no video	Bad video cable	Test with different monitor and cable
Chime, no video	Failed logic board capacitors	Recap logic board
Chime, garbled video	VRAM failure	Replace VRAM SIMMs
Chime, garbled video	Failing capacitors	Recap logic board; check for electrolyte damage
No chime, no video	Dead CPU	Inspect CPU socket; try reseating processor
No chime, no video	ROM failure	ROM chips rarely fail; usually indicates capacitor damage

VRAM Testing

The Quadra 605 requires matched pairs of VRAM SIMMs. Test by:

Removing all VRAM – the system should still boot to a low-resolution display
Swapping VRAM positions
Testing with known-good VRAM

Startup Issues

**Startup Problems**
Symptom	Possible Cause	Recommended Action
Flashing question mark	No bootable system found	Check hard drive connections; boot from floppy or external SCSI
Flashing question mark	Failed hard drive	Replace or test drive externally; consider SCSI2SD/BlueSCSI
Sad Mac icon	Hardware failure	Note the error code; see Sad Mac Error Codes
Freezes during startup	Failing capacitors	Recap logic board
Freezes during startup	RAM problem	Test with only onboard RAM
Freezes during startup	SCSI conflict	Check SCSI ID assignments and termination

Sad Mac Error Codes

See Sad Mac Error Codes for a complete list. Common codes for the Quadra 605:

**Common Error Codes**
Code	Meaning
0000000F	ROM checksum failure or severe hardware problem
0000000E	RAM test failure
00000002	ROM checksum error
0000000D	RAM addressing error

Intermittent Operation

**Intermittent Issues**
Symptom	Possible Cause	Recommended Action
Random crashes	Failing capacitors	Recap logic board and power supply
Random crashes	Bad RAM	Test with different SIMM; try onboard RAM only
Random crashes	Thermal issues	Check ventilation; verify CPU is properly seated
Crashes under load	Power supply weakness	Test voltages under load; recap power supply
Crashes when accessing SCSI	SCSI termination issue	Verify proper termination at end of chain
Crashes when accessing SCSI	Failing hard drive	Test drive; replace with modern SCSI emulator

SCSI Issues

**SCSI Problems**
Symptom	Possible Cause	Recommended Action
Internal drive not recognized	Loose cable	Reseat SCSI and power cables to drive
Internal drive not recognized	Drive failure	Test drive in another system; listen for spin-up
External device not seen	ID conflict	Ensure unique SCSI IDs (0-6, internal drive typically 0)
SCSI errors	Improper termination	Internal drive should be terminated; terminate last external device
Slow SCSI performance	Cable quality	Use proper SCSI cables; avoid excessive cable length

Floppy Drive Issues

**Floppy Drive Problems**
Symptom	Possible Cause	Recommended Action
Disk not ejecting	Worn eject gear	Replace eject gear assembly
Disk not ejecting	Manual eject blocked	Straighten paperclip, insert into emergency eject hole
Read errors	Dirty heads	Clean heads with isopropyl alcohol on cotton swab
Disks not recognized	Failed drive	Test with known-good drive
Constant disk access	Drive capacitor failure	Some drives have internal capacitors requiring replacement

Audio Issues

**Sound Problems**
Symptom	Possible Cause	Recommended Action
No startup chime	Speaker disconnected	Check internal speaker connection
No startup chime	Volume set to zero	Reset PRAM (Cmd-Option-P-R at startup)
Distorted audio	Failing capacitors	Recap logic board
No audio output	Bad capacitors in audio circuit	Recap logic board, paying attention to audio section

PRAM and Settings Issues

If the machine loses settings or shows incorrect date/time:

Replace the 3.6V PRAM battery
Reset PRAM by holding Cmd-Option-P-R during startup until you hear the chime twice
Inspect for battery leakage around the battery holder

Capacitor Failure Symptoms Summary

Many Quadra 605 issues trace back to failed electrolytic capacitors. Suspect capacitors if you see:

Failure to start
Intermittent operation
Audio distortion or no audio
Video problems
Brown or crusty residue on the logic board
Lifted traces or corrosion

See Macintosh Quadra 605 Capacitor Replacement Guide for replacement procedures.

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