Hey all, I have a Garmin VHF in my boat that has been working fine thus far. I last used the boat and have traced an issue back to it. When connected to power it is blowing fuses instantly. I have removed it from the boat and when the power wires are connect directly to battery posts it shoots out sparks and just can't be connected. Any ideas?
Cheers
Most radios use diode protection as a means of preventing further damage (by blowing the fuse - hooking up direct to a battery if something is blowing a fuse isn't a great idea) The diode will typically fail if a reverse polarity condition has been present (even for a split second) and in most sets if an over voltage condition has been present (same deal with the the time frame). When the diode fails it creates a short circuit across the power input which causes the fuse (and any subsequent fuses until the diode is replaced) to blow. Hooking the radio directly to the battery without a fuse while in this condition can cause the printed circuit board to be damaged if it is the "next weakest" current carrying device.
Cheers Scottar, it was fused when connected straight to battery. Thanks for your reply.
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Shorted diode would be same as a working diode provided polarity correct tho? Unless it was a zener that gave overvoltage protection. Even then I would think no difference. Anyways Scrotty - she's stuffed mate. They don't repair these things - buy another.
Not trying to be a smartarse Scottar; always happy to be re-edumucated if I am wrong.
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They aren't in series - they are put across the inputs to complete a circuit in a reverse polarity situation and thus create a short to blow the fuse. In the process they usually destroy themselves though. If it is just a polarity diode and someone has any sort of soldering skills it's not a huge job. We did repair them when I was at Trymax - cheaper than a new one if that's all that was wrong. Give the boys a call - at least worth asking.Originally Posted by TheRealPoMo
I'm pretty handy with most things so I opened it up to have a look. I can't see anything obvious to me but I really don't know what the damaged diode would look like anyway? Might just do the modern thing and throw it away and buy a new one?
Cheers for info guys.
Thanks Scottar, makes sense.
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My diode leaks and get this, it's before the on/off switch on the radio so I have to disconnect the battery or it will go flat in a Month or so.
Having said that scrotty, try connecting the radio with the switch turned off and if it still blows a fuse my money is on the diode being short circuited... SNIP!
Hey Fed, yeah she still blows. I would replace the diode but I don't know which one it is? Cheers
Before the switch is normal for radios at least Fed. Can't ever recall seeing anything different.
I don't do radios scottar they work on magic IMO.
It would have to be between the power socket & the on/off switch scrotty, wired straight across the positive & negative. I don't think you would have to replace it, just cut it out, scottar?I would replace the diode but I don't know which one it is?
There is a little blue barrel looking thing soldered across the positive and negative where the power lead is soldered to the board?
It will work without it but is probably a zenor for overvoltage protection as well and really should be replaced.
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