How to Find the Value of Burnt Resistor using 4 Handy Methods

Electrical Technology

How to Determine the Value of a Burnt Resistor Using Four Simple Methods

When troubleshooting, repairing, or designing electrical and electronic circuits, or working with damaged circuit boards, you may encounter situations where you need to replace damaged components such as capacitors, diodes, or resistors. If you need to determine the value of a burnt resistor, you can use the following four handy methods:

How to find The value of Burnt Resistor?

Method 1

  1. Scrape off the outer coating of the resistor.
  2. Clean the burnt section of the resistor.
  3. Measure the resistance from one end of the resistor to the damaged section.
  4. Measure the resistance from the damaged section to the other end of the resistor.
  5. Add these two resistance values together.

This will give you an approximate value of the burnt resistor. Add a small resistance value to account for the damaged section. For example, if you measure 970 Ω and the original value was 1k Ω, just add 30 Ω to get back to 1k Ω which is the standard size.

Method 2

This method is useful if you’re unfamiliar with resistance color coding and need to find the value of a burnt resistor (or connected resistors in a circuit).

  1. Connect the resistor to a multimeter and measure the voltage drop across it.
  2. Measure the current flowing through the resistor.
  3. Multiply these two values to determine the power rating (P = VI) using Ohm’s Law.

Ensure that the wattage calculated is less than or equal to the wattage of the resistor being replaced.

Method 3

This method is most effective if you know the expected output voltage of the circuit and have a set of resistors with the same wattage as the burnt resistor. Use this method when the resistor value is unknown.

  1. Start with a high resistance value and temporarily connect this resistor in place of the burnt one.
  2. Measure the circuit’s output voltage. If it matches the expected voltage, you’re done.
  3. If you don’t know the expected voltage, gradually reduce the resistance value until the circuit functions as designed.

Method 4

In some cases, the value of the resistors is printed directly on the printed circuit board (PCB). If you encounter a burnt resistor, simply look for its value printed on the circuit board. If the value isn’t printed, use one of the methods described above (1-3). 

Share this article with friends or colleagues if you found it helpful for determining the value of a burnt resistor.

Let us know in the comments if you know any additional methods for finding the value of burnt resistors.

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