Weird 12V question for you electric gurus...
I'm hoping you guys will be able to troubleshoot this for me as I am totally baffled... Background: -In our former TV cabinet, we had a 12V outlet on the same plate as the coax jack. It didn't wor...
Forum Discussion
Easiest way to to use your voltmeter. Several ways to do it. If you can find the common ground connection for the fuse panel put your black test lead there. Then with the red lead read the voltage on each side of the fuse. If you have 12V on both sides of the fuse, it's a good fuse. If you have 12V on one side and 0V (or any other reading other than 12V it's a bad fuse).
Alternatively you can check the voltage ACROSS the fuse. If the fuse is good you will read OV across it. If the fuse is bad you will read 12V. I know these readings sound wrong if you aren't experienced in electronics but they are correct. A good fuse has near 0 Ohms resistance and will therefore not drop any voltage- thus the reason it should read OV
The third method is to remove the fuse and check it with the meter on resistance. A good fuse should read near 0 Ohms resistance. An open fuse should read infinity (some meters show "OL", others show a "1" for infinity).
The first two methods are the best as you are testing the fuse under load (actual working conditions). I have had fuses that checked good with an ohmmeter but were actually bad- when the power hit them one end of the element would get hot and disconnect itself from the fuse. This doesn't happen often but one time is enough to make you want to do it using the first two methods. When I was an inexperienced tech, way back when I had this problem and wasted several hours troubleshooting it. I have never forgotten this and therefore use the first two methods.
Sorry if I sound like an Electronics Instructor- that's because I was. After being an electronics tech for 10 years, I taught Electronics for awhile
Good luck
Alternatively you can check the voltage ACROSS the fuse. If the fuse is good you will read OV across it. If the fuse is bad you will read 12V. I know these readings sound wrong if you aren't experienced in electronics but they are correct. A good fuse has near 0 Ohms resistance and will therefore not drop any voltage- thus the reason it should read OV
The third method is to remove the fuse and check it with the meter on resistance. A good fuse should read near 0 Ohms resistance. An open fuse should read infinity (some meters show "OL", others show a "1" for infinity).
The first two methods are the best as you are testing the fuse under load (actual working conditions). I have had fuses that checked good with an ohmmeter but were actually bad- when the power hit them one end of the element would get hot and disconnect itself from the fuse. This doesn't happen often but one time is enough to make you want to do it using the first two methods. When I was an inexperienced tech, way back when I had this problem and wasted several hours troubleshooting it. I have never forgotten this and therefore use the first two methods.
Sorry if I sound like an Electronics Instructor- that's because I was. After being an electronics tech for 10 years, I taught Electronics for awhile
Good luck
