Macintosh Quadra 605 Capacitor Replacement Guide

Replacing electrolytic capacitors (recapping) in your Macintosh Quadra 605 is essential for long-term reliability. This guide also applies to the LC 475, Performa 475, and Performa 476, which share the same logic board and power supply.

After 30+ years, the original surface-mount electrolytic capacitors in these machines are prone to failure and leakage. Electrolyte from failed capacitors is corrosive and can damage traces and components if not addressed.

Capacitor Inspection

Before recapping, inspect the logic board for signs of capacitor failure:

Bulging Tops – Capacitors with domed or swollen tops are failing
Leaking Electrolyte – Brown or orange residue around capacitor bases
Corrosion or PCB Staining – Discoloration on the PCB near capacitors
Lifted or Corroded Traces – Electrolyte has damaged the board

Even if capacitors appear healthy externally, electrolyte can leak from the bottom of the capacitor, hidden from view. Proactive replacement is recommended.

Macintosh Quadra 605 / LC 475 Logic Board Capacitor List

The logic board uses surface-mount tantalum or electrolytic capacitors. Recommended replacements are tantalum capacitors which do not leak like electrolytics.

**Logic Board Capacitor Specifications**
Capacitance	Voltage	Quantity	Recommended Replacement
47µF	16V	Multiple	KEMET T491D476K016AT (tantalum)
100µF	6.3V	Multiple	KEMET T491D107K006AT (tantalum)

Tantalum capacitors are polarized. Observe correct polarity when installing – the stripe on a tantalum indicates the positive lead (opposite of electrolytics where the stripe marks negative).

Recapping Guide Image

Power Supply Capacitor List

The Quadra 605 uses the same power supply as the LC, LC II, LC III, and LC 475. This power supply is also prone to capacitor failure.

The power supply should be recapped along with the logic board for complete restoration.

Warning: Power supplies contain high-voltage capacitors that can retain charge even when unplugged. Allow adequate time for discharge before working inside the power supply. Use appropriate safety precautions.

Capacitor Replacement Procedure

Required Tools

Temperature-controlled soldering iron (recommended 350-380°C for lead-free solder)
Solder wick or desoldering pump
Fine solder (0.5 mm diameter, leaded preferred)
Isopropyl alcohol (90% or higher)
ESD-safe brush or toothbrush
Multimeter
Safety glasses
Flux (no-clean recommended)

Removal Procedure

Disconnect Power – Unplug the machine and remove the logic board from the case.
Document Orientation – Photograph capacitor positions and polarities before removal.
Apply Heat – Heat one side of the capacitor while gently pushing from the side. SMD capacitors will slide off when solder is molten.
Remove Old Solder – Use solder wick to clean the pads thoroughly.
Clean the Area – Remove any electrolyte residue with isopropyl alcohol and a brush.
Inspect Traces – Check for trace damage or corrosion. Repair any lifted or broken traces before installing new capacitors.

Installation Procedure

Apply Fresh Solder – Tin the pads with fresh solder.
Position Capacitor – Place the new capacitor observing correct polarity. For tantalum capacitors, the stripe indicates positive.
Solder Leads – Heat each pad and allow solder to flow around the lead.
Inspect Joints – Joints should be shiny and smooth, not dull or balled.
Clean Flux – Remove flux residue with isopropyl alcohol.
Check for Shorts – Use a multimeter to verify no shorts exist between power rails.

Trace Repair

If capacitor electrolyte has damaged traces:

Scrape away corrosion to reveal clean copper (if any remains).
Use fine wire (30 AWG or similar) to bridge damaged sections.
Solder wire to good portions of the trace on either side of the damage.
Apply conformal coating or clear nail polish to protect the repair.

For severely damaged boards, trace repair may require significant skill. Consider professional repair if damage is extensive.

Testing After Recap

Visually inspect all solder joints.
Check for shorts between power rails with a multimeter.
Reassemble and connect only power (no peripherals).
Power on and verify startup chime.
Connect monitor and verify video output.
Test all functions including audio, floppy drive, and SCSI.

Voltage Verification

After recapping, verify power supply voltages under load:

**Expected Voltages**
Rail	Expected Range
+5V	4.85V – 5.25V
+12V	11.4V – 12.6V

Parts Sourcing

Recommended replacement capacitors:

Tantalum capacitors are preferred over electrolytics because they do not contain liquid electrolyte and will not leak over time.

Additional Resources

Related Maintenance Pages