22-07-2011, 07:41 PM
If you have a wire wound resistor that is open-circuit, you can find out the approximate value. Often older resistors loose their value markings as they fade with the heat from the resistor.
Providing it is the older type, with a 'dipped' coating as opposed to the newer type enclosed in ceramic, the surface can be scraped away to reveal the wound resistance wire. Scrape the surface about half way along the resistor to expose the wire. Using your multi-meter on the resistance setting, measure the resistance from one end of the resistor to the centre. If you get an open-circuit reading, try the other end to centre. Once you have the reading all you need to do is double it. E.g. If you measure 240 ohms then your resistor is likely to be a 470 or 500 ohm.
Roger.
Providing it is the older type, with a 'dipped' coating as opposed to the newer type enclosed in ceramic, the surface can be scraped away to reveal the wound resistance wire. Scrape the surface about half way along the resistor to expose the wire. Using your multi-meter on the resistance setting, measure the resistance from one end of the resistor to the centre. If you get an open-circuit reading, try the other end to centre. Once you have the reading all you need to do is double it. E.g. If you measure 240 ohms then your resistor is likely to be a 470 or 500 ohm.
Roger.
