Reforming Old Electrolytic Capacitors

6 min read Jun 26, 2024
Reforming Old Electrolytic Capacitors

Reforming Old Electrolytic Capacitors: A Guide to Reviving Vintage Electronics


Electrolytic capacitors are a crucial component in many electronic devices, but they can deteriorate over time, leading to reduced performance and eventual failure. If you're working with vintage electronics or repairing old equipment, you may encounter old electrolytic capacitors that need reforming. In this article, we'll explore the process of reforming old electrolytic capacitors and provide a step-by-step guide to help you revive your vintage electronics.

What is Capacitor Reforming?

Capacitor reforming is the process of restoring an old electrolytic capacitor to its original specifications by applying a controlled voltage and current to the capacitor. This process helps to restore the capacitor's dielectric properties, increasing its capacitance and reducing its equivalent series resistance (ESR).

Why Reform Old Capacitors?

Reforming old electrolytic capacitors can be a cost-effective and environmentally friendly way to extend the life of vintage electronics. By reforming the capacitors, you can:

  • Reduce electronic waste: By reviving old capacitors, you can reduce the amount of electronic waste generated by disposing of faulty equipment.
  • Save money: Reforming capacitors can be more cost-effective than replacing them with new ones, especially for rare or hard-to-find components.
  • Preserve vintage electronics: Reforming capacitors can help preserve vintage electronics and keep them functional for years to come.

Preparation and Safety Precautions

Before you start reforming old electrolytic capacitors, make sure you take the necessary safety precautions:

  • Wear protective gear: Wear safety glasses, gloves, and a lab coat to protect yourself from electrical shocks and chemical spills.
  • Use a well-ventilated area: Work in a well-ventilated area to avoid inhaling fumes from the capacitor's electrolyte.
  • Disconnect power: Ensure the equipment is disconnected from power before attempting to reform the capacitors.
  • Check the capacitor's specifications: Verify the capacitor's voltage and capacitance ratings to ensure you're using the correct reforming process.

Reforming Process

The reforming process involves applying a controlled voltage and current to the capacitor. Here's a step-by-step guide:

Step 1: Inspect the Capacitor

Visually inspect the capacitor for signs of physical damage, such as cracks, corrosion, or leakage. Check the capacitor's markings for the voltage and capacitance ratings.

Step 2: Choose the Reforming Method

There are two common reforming methods:

  • DC Reforming: Apply a DC voltage to the capacitor, gradually increasing the voltage to the rated value over a period of hours or days.
  • AC Reforming: Apply an AC voltage to the capacitor, typically using a variac or a transformer, to create a gentle AC voltage stress.

Step 3: Apply the Reforming Voltage

Connect the capacitor to a power source, such as a variac or a DC power supply, and apply the reforming voltage. Monitor the capacitor's voltage and current to ensure it's within safe limits.

Step 4: Monitor and Adjust

Monitor the capacitor's voltage, current, and temperature during the reforming process. Adjust the voltage and current as needed to avoid overheating or excessive current flow.

Step 5: Verify Capacitor Performance

After the reforming process, verify the capacitor's performance using a capacitance meter or an oscilloscope. Compare the results to the capacitor's original specifications to ensure it's within acceptable limits.


Reforming old electrolytic capacitors can be a rewarding process that helps preserve vintage electronics and reduces electronic waste. By following the guidelines and safety precautions outlined in this article, you can successfully reform old capacitors and bring your vintage electronics back to life.

Additional Resources

  • Capacitor reforming tutorials: Online resources, such as YouTube tutorials and forums, can provide additional guidance and tips for reforming old capacitors.
  • Capacitor datasheets: Consult the capacitor's datasheet for specific reforming instructions and guidelines.
  • Electronics forums: Online forums, such as Reddit's r/LearnElectronics, can provide a community-driven approach to learning about capacitor reforming and electronics repair.