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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / July 2006Inline Fuse For CB Power Cord
Plugged in one of the CB radio's today ( in the Buick ) and the 2 amp inline fuse blew. Could this of been caused by the wires being two different sizes? The wires coming out of the lighter plug going to the fuse holder are about 2 sizes bigger than the wire coming out of the fuse holder going to te back of the CB radio. Tried two other CB's and they worked fine. harryface 05 Park Avenue 41,698 91 Bonneville 307,076 No. > Plugged in one of the CB radio's today ( in the Buick ) and the 2 amp > inline fuse blew. [quoted text clipped - 10 lines] > 05 Park Avenue 41,698 > 91 Bonneville 307,076 > Plugged in one of the CB radio's today ( in the Buick ) and the 2 amp > inline fuse blew. [quoted text clipped - 10 lines] > 05 Park Avenue 41,698 > 91 Bonneville 307,076 No, is my vote also. You could plug the fused wire directly to the positive post of the battery and blow no fuse if all else is ok--and look at how big that post is as compared to the fused wire! Has always been easy for me to carelessly short a wire when checking a temporary 'rig'. HTH & good luck, s Sounds like that radio got hooked up in reverse sometime. It takes less than a second to blow the reverse polarity protection diode in the radio. Once it goes it will blow fuses regardless of what size you use. Not a hard repair if you own a soldering iron and can find a Radio Shack to buy a replacement diode from. (99% of AM only rigs can use a 1N4001, AM/SSBs use 1N4007 due to the higher current draw on them) It is an easy part to find. Just open the case and look for a large diode right next to the area the power wires are soldered to the board. It will look like the ones you bought. Just desolder it after making a note of it's orientation (which way the band goes) and solder in the new one. Clip the leads, put the case back together and hook it back up.  SignatureSteve W. > > Plugged in one of the CB radio's today ( in the Buick ) and the 2 amp > > inline fuse blew. [quoted text clipped - 16 lines] > Has always been easy for me to carelessly short a wire when checking a > temporary 'rig'. HTH & good luck, s >Sounds like that radio got hooked up in reverse sometime. It takes less >than a second to blow the reverse polarity protection diode in the >radio. Once it goes it will blow fuses regardless of what size you use. A reverse polarity protection diode isn't going to conduct at all. That's what the word "protect" means. It won't go and it won't blow fuses. > >Sounds like that radio got hooked up in reverse sometime. It takes less > >than a second to blow the reverse polarity protection diode in the > >radio. Once it goes it will blow fuses regardless of what size you use. > > A reverse polarity protection diode isn't going to conduct at all. > That's what the word "protect" means. It won't go and it won't blow fuses. This is normally the case, but in my experience I have found some blown diodes that wind up causing a short. This is usually because when they burnt out, the solder connection melted and shorted the circuit to ground. A visual inspection of the diode is all that is needed to verify its condition. If it is melted it is probably shorted. If it looks ok it might still be blown (open circuit), but would not be causing a short circuit. SignatureKevin Mouton Automotive Technology Instructor "If women don't find you handsome, they should at least find you handy" Red Green >This is normally the case, but in my experience I have found some blown >diodes that wind up causing a short. This is usually because when they burnt >out, the solder connection melted and shorted the circuit to ground. A >visual inspection of the diode is all that is needed to verify its >condition. If it is melted it is probably shorted. If it looks ok it might >still be blown (open circuit), but would not be causing a short circuit. Are you talking about a series diode or a parallel diode? A series diode would simply not conduct. A parallel diode would be in series with the fuse. The diode would never be sized where it would be damaged; the fuse would blow and then there would be no more current through the circuit. Are you doing anything silly like using a fuse larger than originaly engineered? > >This is normally the case, but in my experience I have found some blown > >diodes that wind up causing a short. This is usually because when they burnt [quoted text clipped - 12 lines] > Are you doing anything silly like using a fuse larger than originaly > engineered? The OP said he hooked it up in reverse polarity and suspects he burnt out a diode. I was just commenting that a burnt diode is not always an open circuit. They can and sometimes do produce a short to ground when they burn. SignatureKevin Mouton Automotive Technology Instructor "If women don't find you handsome, they should at least find you handy" Red Green >> >This is normally the case, but in my experience I have found some blown >> >diodes that wind up causing a short. This is usually because when they [quoted text clipped - 14 lines] >> Are you doing anything silly like using a fuse larger than originaly >> engineered? >The OP said he hooked it up in reverse polarity and suspects he burnt out a >diode. I was just commenting that a burnt diode is not always an open >circuit. They can and sometimes do produce a short to ground when they burn. A series diode can't produce a short to ground. It isn't connected there. You need to get an understanding of what a diode is and how they operate. A series diode will *never* short out if power is connected backwards. It simply will not conduct. A parallel diode might burn out, but the fuse should protect it. Diodes are not fuses. The fuse is there to protect the circuit, not the other way around. More likely, there wasn't any protecting diode at all and the radio was severely damaged by the reverse connection. Time to toss it out and get a new one. > >> >This is normally the case, but in my experience I have found some blown > >> >diodes that wind up causing a short. This is usually because when they [quoted text clipped - 31 lines] > was severely damaged by the reverse connection. Time to toss it > out and get a new one. I understand your point and I agree that the radio is probably toast. A burnt diode in series will produce an open circuit. However I guess I failed to properly explain my point, which is that a burnt diode may not always produce an open circuit but may actually become bridged and not function as a diode anymore. I guess you would say it becomes a closed circuit which will pass current in either direction rather than a short to ground, but in any case, it will not always produce an open circuit when it fails.. Nothing to do with the radio, but case in point would be a burnt diode on an alternator rectifier might actually cause a parasitic drain on the battery by causing a short to ground through the stator. That is all I was trying to say. I do agree that this probably has nothing to do with the radio in question and I should have brought up the subject in a different manner. My mistake. SignatureKevin Mouton Automotive Technology Instructor "If women don't find you handsome, they should at least find you handy" Red Green > Plugged in one of the CB radio's today ( in the Buick ) and the 2 amp > inline fuse blew. [quoted text clipped - 10 lines] > 05 Park Avenue 41,698 > 91 Bonneville 307,076 Nah. The max power usage of the radio is probably less than 2 amps. 4 watts out ~= 12 watts in = 1 amp. My guess is the fuse was bad. They go bad from internal corrosion. A splice that had screw caps under the electrical tape came loose. Soderd the wires together then used heat shrink tubing to seal it . harryface |
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