When repairing a faulty electronic device, you find a burnt resistor on the board, how can you determine its value? All the markings on it have faded and it is not possible to measure the resistance with a multimeter. If you're lucky, you can find a circuit diagram on the Internet, but what if it's not available anywhere? This life hack from an experienced radio amateur will help you.
Will need
- Stationery knife or scalpel.
- Multimeter or ohmmeter.
The procedure for determining the value of a burnt resistor
The first step is to remove the burnt resistor from the board.
Usually resistors burn in the center or at the edges. Therefore, use a knife to carefully remove the burnt paint from the center. Our task is to get to the resistive layer.
(The life hack, for clarity, is demonstrated on a large, working 2-Watt resistor.) Next, turn on multimeter. We connect one probe to one terminal, and place the other exactly in the center.
If there are no readings, then we turn the resistor over and connect another terminal and connect the second probe in the same way to the center.
So, we measured half the resistance of the resistor.We multiply the value by two and get the approximate value of the resistor that previously worked. Of course, the method will not give a 100% accurate result, but it will be quite possible to select a denomination with a slight deviation.
If the center of the resistor has burned out significantly and there is simply nothing to measure in the center, then visually divide the resistor not into 2 parts, but into 3 parts. Measure on one side and multiply the reading by three.
This is some useful advice that will come in handy someday.
