Macintosh Plus Capacitor Replacement Guide

Replacing electrolytic capacitors (recapping) in your Macintosh Plus is essential for long-term reliability, stable voltages, and a crisp video image. Over time, capacitors degrade, leading to voltage instability, display artifacts, and system failure. Proactively replacing these components ensures continued functionality.

🔍 Capacitor Inspection

Before replacing capacitors, inspect each one for signs of deterioration:

• Bulging Tops – Capacitors should have a flat top. Swelling or doming indicates failure.
• Leaking Electrolyte – A brown or white crust around leads shows electrolyte leakage.
• Corrosion or PCB Staining – Indicates internal leakage and should prompt immediate replacement.

📋 Macintosh Plus Capacitor List

🧯 Analog Board Capacitors

Macintosh SE Analog Board Capacitors (identical layout to Plus)

The Macintosh Plus analog board contains many large electrolytic capacitors that should be replaced proactively:

Analog Board Capacitor Specifications

Label	Capacitance	Voltage	Quantity
C1	3.9µF	35V	1x
C2	4700µF	16V	1x
C3	220µF	16V	2x
C5	47µF	10V	1x
C6	22µF	50V	2x
C10	33µF	16V	2x
C11	10µF	160V	1x
C12	22µF	50V	2x
C18	33µF	16V	2x
C24	2200µF	16V	4x
C27	2200µF	16V	1x
C28	1000µF	16V	1x
C30	2200µF	16V	1x
C31	220µF	16V	1x
C32	2200µF	16V	1x
C33	4700pF	250V	2x
C34	100µF	200V	4x
C35	100µF	200V	1x
C36	4700pF	250V	1x
C37	0.47µF	250V	1x
C38	100µF	200V	1x
C39	100µF	200V	1x
C42	470µF	10V	2x
C45	470µF	10V	1x

🔧 Logic Board Capacitors

Macintosh Plus Logic Board Capacitor Locations

The Macintosh Plus logic board contains fewer electrolytic capacitors than the analog board but they are still critical for operation.

Macintosh Plus Logic Board Capacitor Specifications

Label	Capacitance	Voltage	Quantity
C5	33µF	16V	1x
C20	33µF	16V	1x
C22	4.7µF	35V	1x

🛠️ Capacitor Replacement Procedure

1. Discharge CRT – Safely discharge the CRT before any internal work.
2. Remove Boards – Label and disconnect cables; remove analog and logic boards.
3. Desolder Old Caps – Use a soldering iron, wick, or pump to cleanly remove components.
4. Insert Replacements – Observe correct polarity (marked with a stripe).
5. Solder Securely – Ensure joints are shiny, clean, and well-adhered.
6. Trim Leads & Inspect – Trim excess leads and double-check all work.
7. Check for Shorts – Use a multimeter to verify no shorts before powering on.

🧰 Recommended Tools

• Temperature-controlled soldering iron
• Desoldering pump or braid
• Fine leaded solder (0.5 mm)
• Isopropyl alcohol & ESD brush
• Multimeter
• Safety glasses & gloves

⚙️ Voltage Adjustment After Recap

Use a multimeter to verify voltages at the floppy drive power connector:

• +5V rail: 4.85V – 5.15V
• +12V rail: 11.9V – 12.7V

Adjust using the analog board's trimmer potentiometer (R56) if needed.

💡 Additional Tips

• Power the Mac periodically to prolong capacitor life.
• Use brand-name capacitors (e.g., Nichicon, Panasonic, Rubycon).
• Replace in groups or full sets for best results.
• Always verify polarity and double-check each joint.
• Dispose of old capacitors via proper e-waste channels.

🔗 Related Maintenance Pages

• Macintosh Plus Troubleshooting
• Macintosh Plus General Maintenance
• CRT Discharge Procedure