Electrical oddity solved - SailNet Community
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post #1 of 21 Old 12-09-2019 Thread Starter
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Electrical oddity solved

I was getting some new handrails welded to the deck which required me to pull down the headliners and handle the wire lighting, some of which I extended to make it easier to work with.

When done I turned on a LED and it was very dim, but on. Same with a second LED on the same circuit. But the halogen light and fans were not working. What the heck! I could not imagine what would do that.

It turns out it was a simple blown fuse. Replace and now all works as intended. So why did the lights work at all if there was a clearly blown fuse.

My only explanation is that there is enough ACBfloating around inside the (completely steel encased) saloon that the LED DIODES could pick it up, rectify it and use it to power the lights, albeit dimly.

Frankly I find this amazing as I don’t recall having anything turned on. Maybe the VHF and the Fridge. But we are a very simple boat hanging on the hook. No AC power and the inverter was turned off. We do have solar and a wind generator but both of them output DC.

Maybe one of these days when I’m VERY bored I’ll pull the fuse and see if I can trace to source of the induction.

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post #2 of 21 Old 12-09-2019
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Re: Electrical oddity solved

Why did the fuse blow? Pull it and vm to ground at a light and at the output side of the fuse holder. Or leave an Led on while the fuse is out and watch while you remove other fuses one by one. If the light goes out that's the circuit that's shorting. Or just forget it and wait for the smell of burning wiring when the short gets to ground.
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post #3 of 21 Old 12-10-2019
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Re: Electrical oddity solved

Yup, I'd start testing for a short, especially in a metal boat, iirc.


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post #4 of 21 Old 12-10-2019 Thread Starter
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Re: Electrical oddity solved

I was pulling the headliners down. I cut the light wires to extent them. I probably just shorted the wires with my dikes.

Geeze guys relax with the paranoia and doom.
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Re: Electrical oddity solved

Huh? Suggesting you look for a short, after posting that lights were on, even though the fuse was blown is paranoia? Why did you post it then?

I don't follow how your dikes may have been the problem, but I can't tell if you want to discuss it at all.


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post #6 of 21 Old 12-10-2019 Thread Starter
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Re: Electrical oddity solved

Minn,

The power was on when I cut the wires. If I accidentally shorted the wires with my dikes then I would have blown the fuse.

I said the LED lights were on very dim, the fans would not run and the halogen light didn’t work at all. That tells you that the problem is a very low source of current and also that it is likely AC.

Why low current? Because the Halogen did not even begin to heat up.
Why AC? Because it is likely being rectified over the diodes in the lamps. Could be wrong, been a lot time since I did bench work.

In any case since I replaced the fuse everything is working OK.

When I take the fuse out then the lamps no longer work. No even dimly. NADA. So I am suspecting that what ever the source of AC was is now off.

Why did I post this? Because I was surprised by the symptoms and thought it might be interesting to share. Maybe someone else has seen something similar or has a different theory.

I was certified as a bench electronics technician in 1973 but it’s been a looong time since I’ve done real electronics work.

With today’s electronic volt meters it is very common, almost normal, to see stray voltage on wires that are not connected. Back in the day when a Simpson 260 was the go to industry standard meter, it would apply some resistance across the circuit, 20,000 ohms/volt, for what ever scale you were using. This “short” was generally enough to “quiet” these minuscule voltages. Today’s meters have vastly higher ratings, but then you see these voltages and they can confuse you. It’s almost better to use an dl cheap movement type for this reason. So I’m far from suprised to see some voltage on a “dead” line, I was surprised it was enough to get some light out of an LED.

If nothing else it’s an interesting story.

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Last edited by hpeer; 12-10-2019 at 08:51 AM.
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post #7 of 21 Old 12-10-2019
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Re: Electrical oddity solved

Were/are the LED's on a dimmer? Often, the dimmers when "off" keep the LEDs active at a very low glow - can't see them during daylight.

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Re: Electrical oddity solved

Nope, no dimmer.

I think we were posting over one another, and I had to correct a bunch of spell checker enhanced spelling.

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post #9 of 21 Old 12-10-2019
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Re: Electrical oddity solved

Sounds an example of an electric personality

Don't blow air up my rear, be useful and blow it at the sails!
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Re: Electrical oddity solved

Quote:
Originally Posted by Don L View Post
Sounds an example of an electric personality
Must be, my Wife finds me “shocking”.

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