Minor electrical issue here...

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Oct 15, 2008
6
Lancer 28 Chula Vista Marina, San Diego, Ca
So I'm scratching my head on this one; I bought one of those computer theater system type setups, that work off an ac power supply, and plug into either a computer, mp3 player, ipod, etc, through a 1/4 inch jack. I use my laptop as a "jukebox" of sorts on my boat, and when I'm docked, and have shorepower running to the outlets, it works great. I have the stereo's 5 speakers strategically placed throughout the boat that gives it a really good surround sound. However, when underway, the first time I tried to use it on the water, I plugged the adapter into my power inverter, and it fried the ac power supply, as well as the master control speaker. I searched high and low for a suitable replacement ac adapter, but ultimately ended up just buying the very same setup, and junking the old one. This time, I ran a surge protector between the inverter and the power supply to the speakers, and when I turned on the inverter, it flips the surge protector immediately. I've found that if I have my car jumpstart/air compressor/inverter box on the boat, I'm able to plug the speakers' power supply straight in and have no problems until it runs down, which is after about 2 hours. What I'm wondering, is why it won't work with my inverter? It's a West Marine 400 watt inverter, and the specs on the power supply for the speakers, says it's 115v input, and 15 v output, and 1300 mA output. Do I need a bigger or smaller inverter, or what? I know it can't be due to the battery size, because last time I was out with friends off the coast by Point Loma, the emergency car charger thingy I mentioned earlier died, but I was able to put the jumper cables from it to my battery, and flipped it to "jumpstart mode", and it continued to work for about another hour before it wouldn't hold a charge. Let me know if anyone has any insight for me here, because I really feel like this is "jerry-rigging" , and I don't want to fry anything, since I've already completely gutted and redid my boat's whole electrical system, and the thought of roasting wires and/or causing a fire out on the water makes me crap my pants. Thanks!

- J
 
Feb 17, 2006
5,274
Lancer 27PS MCB Camp Pendleton KF6BL
Well, after reading what you have Justin, I am wondering if you have a short in the system or you are drawing too much current. What else do you have plugged in that is using AC? You mentioned computer and such. Any other electrical items? The other possibility is the wiring on the output of the inverter is not correct. If you are plugging directly into the inverter then that is moot. But if you are extending the inverter to your AC outlets, you could have you wiring crossed.

AC uses three wires; Hot, neutral, and ground. In the old days two wires was the norm, one could change the hot and neutral and get away with it. Maybe be a hum or slight shock then one would reverse the plug. But now with modern equipment, three wires are the standard. I would make sure that your hot and neutral were wired correctly.

You might want to run over to Radio Shack and get one of those AC line tester plugs. They have LED display that tells you if you are reverse polarity or if you have a short or even an open. Test with the shore power connected and test without the shore power. But regardless, calculate your AC electrical budget and make sure you are not exceeding the specs. There maybe something plugged in that you are forgetting.
 

BobM

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Jun 10, 2004
3,269
S2 9.2A Winthrop, MA
Need a better inverter

You likely need a better inverter.

Cheaper models mimic AC current (modified wave) while better models provide exactly what your house would produce (pure wave). This could affect sensitive electronics. See attached. Be warned...a pure wave inverter is about 5X more expensive.

http://www.donrowe.com/inverters/inverter_faq.html#modified
 
Oct 15, 2008
6
Lancer 28 Chula Vista Marina, San Diego, Ca
The power inverter I'm using when underway, is that 400w West Marine special, that has the 2 gator clips that clip directly onto the battery terminals, and then you plug whatever your using into the outlets on the face of the inverter. When I fried the speaker setup the first time, it was the only thing plugged into it. I can plug my laptop directly into the same inverter, with no problems, it charges up my laptop, and everything's honky dory. But like I said, when I ran a surge protector from the outlet in the face of the inverter, and then plugged in the speaker's power supply to the surge protector, it flipped the protector's fuse everytime. The entire speaker setup is 80 watts, so I figured a 400w inverter would have been more than enough. Blows me away, because I'm pretty sure that my laptop draws about the same, if not a little more, when plugged into it, and it works.
 
Oct 9, 2007
17
McGregor 26 Napa, CA
I agree with Bob -- make sure you are getting a pure sine wave and not a square wave simulating the sine wave -- you should be able to buy a cheap one rated at about 75 watts hat should do the job.
 
Feb 17, 2006
5,274
Lancer 27PS MCB Camp Pendleton KF6BL
Justin, do you have access to an Oscilloscope? If so, take your inverter and with the O'Scope, check to see what the wave looks like. That might confirm what type of inverter you have.
 

BobM

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Jun 10, 2004
3,269
S2 9.2A Winthrop, MA
Laptop

Your laptop won't have a problem because it actually converts AC to DC via the transformer pack that is in line. Any sensitive electronics that don't really run on DC (no "wall wart" or in line transformer on the power cable) may have problems.

If it has one (you mention an AC power supply) you should look at the specifications on it. If it is putting out 12 volts, just wire it to your 12V system after cutting off the AC wall wart, or buy appropriate substitue wiring from Radio Shack. If it is 9V instead of 12V it may still work, or you will need to step down the voltage, which is inexpensive to accomplish using a DC to DC converter.

See http://www.powerstream.com/dc6.htm

I am convinced you do not have a pure sine wave converter just based on cost, even though West Marine's site isn't clear regarding that model.
 
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