Replacing Reverse Protection Diode?

NatersXJ6

Explorer
So, my CB recently mysteriously started blowing fuses as soon as they touch the fuse holder terminals. My best efforts at google searching seem to indicate that the “Reverse Protection” diode has failed.

I’m not concerned about my ability to solder in a new one, but ai am concerned about why it failed.

So far as I know, the polarity is not reversed. The system worked for a while, then I had an antenna cable problem and didn’t use it for a long time while I replaced and rerouted the cable. I also soldered on a new, longer mic cable. This involved soldering the mic and the connector to a new cable.

After this, fuse failures started.

Could I have done this? What else can cause this?

The diodes are ultra cheap, but it appears that I have to buy a package of 100. Does that mean they are crap and will fail all the time?

I think I need one of you experienced electronics and comms guys to weigh in here.

CB is also cheap... Uniden PRO 510XL.

100 diodes will cost 1/2 as much as replacing the unit. The pin comes from my under driver seat mount that will take several hours to swap.

Thanks for the knowledge!
 

dreadlocks

Well-known member
digikey.com or mouser.com, used to be able to get that kinda stuff at Radio Shack, but alas those days are long gone..

Sounds like you shorted something out when you did the mic, if you take the mic out of the equation does the fuse popping stop? Diodes are usually pretty robust and wont just keep chewing through em unless something is terribly wrong elsewhere..

You got a multimeter? slap that sucker into continuity mode and see if the diode works and probe around for a short.
 

NatersXJ6

Explorer
Thanks. I was thinking maybe I shorted something when I did the mic too, but it seems strange to me that the fuse pops before the power is turned on, and I can’t imagine the mic impacting anything before the power is turned on.

I’m going to have to dig it out from under the seat start bench testing I guess.

Under the seat seems like a great mounting place until something doesn’t work... hmmm...
 

dreadlocks

Well-known member
alot of circuit switching is on ground using mosfets, meaning as soon as you provide power most of the hot rail is energized and its just got a floating ground until it switches on, so its very easy to have a fault that will pop yer fuse the moment you plug it in.
 

762X39

Explorer
So, my CB recently mysteriously started blowing fuses as soon as they touch the fuse holder terminals. My best efforts at google searching seem to indicate that the “Reverse Protection” diode has failed.

I’m not concerned about my ability to solder in a new one, but ai am concerned about why it failed.

So far as I know, the polarity is not reversed. The system worked for a while, then I had an antenna cable problem and didn’t use it for a long time while I replaced and rerouted the cable. I also soldered on a new, longer mic cable. This involved soldering the mic and the connector to a new cable.

After this, fuse failures started.

Could I have done this? What else can cause this?

The diodes are ultra cheap, but it appears that I have to buy a package of 100. Does that mean they are crap and will fail all the time?

I think I need one of you experienced electronics and comms guys to weigh in here.

CB is also cheap... Uniden PRO 510XL.

100 diodes will cost 1/2 as much as replacing the unit. The pin comes from my under driver seat mount that will take several hours to swap.

Thanks for the knowledge!
The last time I purchased diodes (1N4007) for the shop they were about 1.5 cents a piece by the hundreds. Higher current diodes are a bit more. In your case it is protection against reverse polarity. It is a bit hard to troubleshoot your problem without at least a VOM and the understanding to use it. If you can solder and use a meter it should be pretty easy to fix your problem. The diode doesn't typically fail easily. They are cheap because that is all they are worth. Good luck.
 

DaveInDenver

Middle Income Semi-Redneck
If your fuse blows right after you connect power and before you switch on power there's not much in a 510 that could be at fault. The only gotcha to reverse polarity diodes is to make sure it can handle more current than the fuse you're using to protect the feed. You want the fuse to let go first.

Screen Shot 2019-08-11 at 9.33.19 PM.png

But I would also make absolutely sure you don't have a short in the wiring, maybe a kinked power lead, something got stepped on, caught in a seat rail slider, cut on a feed-thru in sheet metal, that sort of thing.
 
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