Talk:Macintosh Classic II Capacitor Replacement Guide

Replacement caps recommendation

Tantalum Capacitors:

Failure Mode: Tantalum caps can fail as a short circuit, especially if subjected to overvoltage, reverse polarity, or defects. A short can indeed pass unregulated voltage to downstream components (e.g., ICs), causing catastrophic damage. However, some tantalums are surge-robust (Kemet T495 up to 1.5x rated voltage) and have low failure rates when properly selected and installed.

Advantages: Extremely long lifespan (>200,000 hours at 40 °C), no electrolyte leakage, compact size, and stable capacitance over time.

Risks: If installed incorrectly (e.g., reverse polarity) or if the power supply has significant spikes (common at Macs startup), a short could damage components. Overrating voltage (e.g., 35V instead of 25V) mitigates this risk significantly.

Solid Polymer Capacitors (Aluminum Polymer SMD):

Failure Mode: Aluminum polymer caps typically fail open or with high resistance, meaning they stop conducting rather than shorting. This is safer for vintage hardware, as an open failure prevents voltage from feeding directly into sensitive ICs, reducing the risk of collateral damage. Failures are rare and usually due to extreme overvoltage or mechanical stress, but polymers are more forgiving.

Advantages:

Safer Failure Mode: Open failure minimizes risk to downstream components.

Lower ESR: Typically 20–100 mΩ (vs. 200+ mΩ for T495 tantalums), improving stability and reducing heat.

High Ripple Current: Handles power fluctuations well, ideal for power rails.

Long Lifespan: 2,000–10,000 hours at 105 °C (translates to >50,000 hours at 40 °C), sufficient for vintage gear.

No Leakage: Solid polymer electrolyte eliminates the corrosion issues of original wet aluminum electrolytic.

Disadvantages:

Slightly larger footprints for high capacitance

Shorter lifespan than tantalums at high temperatures (irrelevant for ~40 °C)

Higher cost than standard aluminum electrolytics (0.50–2 €/piece).

Are Polymer Caps Safer? Yes, due to open failure mode, which prevents shorts that could damage ICs. Low ESR and high ripple tolerance are excellent for power supply and filtering. Tantalums remain reliable when overrated and installed correctly, but the risk of a short-circuit failure makes polymers a better choice for vintage electronics. I recommend SMD Aluminum Polymer Capacitors from reputable brands (Nichicon, Panasonic, Rubycon) with slightly overrated voltage.

Below are recommended polymer capacitors, ensuring compatibility with the Classic IIboard (Rev.B) and all are SMD, RoHS, low ESR (20–100 mΩ).

• 1 µF 50V → 100V, ~4,5mm wide (1812 SMD) e.g. Kemet C1812Y105K1RACAUTO (Y-series short proof)
• 10 µF 16V → 20V, ~5mm wide e.g. Panasonic 20SVPA10M (5mm max width!)
• 47 µF 25V → 35V, ~6.3 mm wide e.g. Panasonic EEH-ZC1V470V I have done the recap with these caps, they are short proof, anti-leakage and it does work. My Classic II is alive again. For 10 µF 20V caps the 5mm diameter is the maximum width, so 25V do not fit, because soldering points are then under the cap. 20V on 12V rail is over dimensioned anyway and will last even longer than original 16V. Put solder on the pads, place the cap on the soldered pads and heat the pads with soldering iron and push down. The other caps are easy to solder.

2A09:BAC2:F0:478:0:0:72:109 11:45, 28 September 2025 (BST)

Changes added! Thank you!!!!!!!!!!! Josh (talk) 15:05, 28 September 2025 (BST)

Tantalum Capacitors:

Failure Mode: Tantalum caps can fail as a short circuit, especially if subjected to overvoltage, reverse polarity, or defects. A short can indeed pass unregulated voltage to downstream components (e.g., ICs), causing catastrophic damage. However, some tantalums are surge-robust (Kemet T495 up to 1.5x rated voltage) and have low failure rates when properly selected and installed.

Advantages: Extremely long lifespan (>200,000 hours at 40 °C), no electrolyte leakage, compact size, and stable capacitance over time.

Risks: If installed incorrectly (e.g., reverse polarity) or if the power supply has significant spikes (common at Macs startup), a short could damage components. Overrating voltage (e.g., 35V instead of 25V) mitigates this risk significantly.

Solid Polymer Capacitors (Aluminum Polymer SMD):

Failure Mode: Aluminum polymer caps typically fail open or with high resistance, meaning they stop conducting rather than shorting. This is safer for vintage hardware, as an open failure prevents voltage from feeding directly into sensitive ICs, reducing the risk of collateral damage. Failures are rare and usually due to extreme overvoltage or mechanical stress, but polymers are more forgiving.

Advantages:

Safer Failure Mode: Open failure minimizes risk to downstream components.

Lower ESR: Typically 20–100 mΩ (vs. 200+ mΩ for T495 tantalums), improving stability and reducing heat.

High Ripple Current: Handles power fluctuations well, ideal for power rails.

Long Lifespan: 2,000–10,000 hours at 105 °C (translates to >50,000 hours at 40 °C), sufficient for vintage gear.

No Leakage: Solid polymer electrolyte eliminates the corrosion issues of original wet aluminum electrolytic.

Disadvantages:

Slightly larger footprints for high capacitance

Shorter lifespan than tantalums at high temperatures (irrelevant for ~40 °C)

Higher cost than standard aluminum electrolytics (0.50–2 €/piece).

Are Polymer Caps Safer? Yes, due to open failure mode, which prevents shorts that could damage ICs. Low ESR and high ripple tolerance are excellent for power supply and filtering. Tantalums remain reliable when overrated and installed correctly, but the risk of a short-circuit failure makes polymers a better choice for vintage electronics. I recommend SMD Aluminum Polymer Capacitors from reputable brands (Nichicon, Panasonic, Rubycon) with slightly overrated voltage.

Below are recommended polymer capacitors, ensuring compatibility with the Classic IIboard (Rev.B) and all are SMD, RoHS, low ESR (20–100 mΩ).

• 1 µF 50V → 100V, ~4,5mm wide (1812 SMD) e.g. Kemet C1812Y105K1RACAUTO (Y-series short proof)
• 10 µF 16V → 20V, ~5mm wide e.g. Panasonic 20SVPA10M (5mm max width!)
• 47 µF 25V → 35V, ~6.3 mm wide e.g. Panasonic EEH-ZC1V470V I have done the recap with these caps, they are short proof, anti-leakage and it does work. My Classic II is alive again. For 10 µF 20V caps the 5mm diameter is the maximum width, so 25V do not fit, because soldering points are then under the cap. 20V on 12V rail is over dimensioned anyway and will last even longer than original 16V. Put solder on the pads, place the cap on the soldered pads and heat the pads with soldering iron and push down. The other caps are easy to solder.

2A09:BAC2:F0:478:0:0:72:109 11:46, 28 September 2025 (BST)