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
The Macintosh Plus analog board contains many large electrolytic capacitors that should be replaced proactively:
| 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
The Macintosh Plus logic board contains fewer electrolytic capacitors than the analog board but they are still critical for operation.
| Label | Capacitance | Voltage | Quantity |
|---|---|---|---|
| C5 | 33µF | 16V | 1x |
| C20 | 33µF | 16V | 1x |
| C22 | 4.7µF | 35V | 1x |
Capacitor Replacement Procedure
- Discharge CRT – Safely discharge the CRT before any internal work.
- Remove Boards – Label and disconnect cables; remove analog and logic boards.
- Desolder Old Caps – Use a soldering iron, wick, or pump to cleanly remove components.
- Insert Replacements – Observe correct polarity (marked with a stripe).
- Solder Securely – Ensure joints are shiny, clean, and well-adhered.
- Trim Leads & Inspect – Trim excess leads and double-check all work.
- 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.