I am trying to repair a charger for my electric drill, and I found a burned up resistor.... dog boned, ceramic?, BROWN bands on both ENDS, and 2 black bands... picture attached.... any help please??
It's large because it's 1 watt instead of 1/4 watt. The 4th band is tolerance, that one is 1% (Brown = ±1%; Red = ±2%; Green = ±0.5%; Blue = ±0.25%) You have to go by the gap between the bands on these, the gap is near the tolerance band.
More importantly, did you find what burned it out? Resistors don't usually just burn out on their own.
i have NO idea... just found it not chargin one day... i dissassembled the case, and while plugged in inserted a drill battery and wiggled it around... the LED lit breifly, then out.. that resistor was quite warm, and when i poked it with a dowel, the LED again lit breifly... checked with a multimeter, and no voltage across it....
Put in a 10R 1watt resistor and feel hot hot it gets after 10 minutes. Remember, a 10R resistor will allow the battery to charge at 300mA.
What is the mAHr rating of the battery.
Try a 10R (brown black black silver or gold) resistor of the same size or larger than the one on the PC board. Turn on the circuit and feel the resistor with your finger after 10 minutes of charging the battery in the drill. It you cannot hold your finger on the resistor, it is getting too hot. If the resistor smells or smokes it is getting too hot.
If it gets too hot, put another 10R in series with it.
You should not do that. This will double your charging current. To lower heating with same current you could use two 20 ohm resistors in parallel or use 10 ohm with higher power rating.
Jirka