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Old 24-01-2011, 11:01   #1
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Installing a 12vdc Television ?

After having our boat now for about a year, my son and daughter would like to catch up on watching some DVD's in the cabin while mom and dad are trying to relax while sailing.

I have narrowed my search to the following Naxa brand 12v LCD/DVD combo: Naxa NX-550 13-inch 1080i LCD TV/ DVD Combo (Refurbished) | Overstock.com

I would like to hardwire this into my electical panel. In order to properly install the TV, do you cut the power cord and hardwire it directly into the DC electrical panel? Is it necessary to wire in a fuse for additional protection?

Also, how long can you run a tv like this before running down the house and starting battery become a concern?

Thanks for your help.
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Old 24-01-2011, 11:17   #2
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Make certain you get the 12VDC polarity correct by measuring the polarity with a multimeter at the wall adapter where you cut the wire. Usually with wall adapters, one wire is slightly different from the other in some way so you can note the polarity. An inline fuse would be advisable. Fuse it slightly above the output of the wall adapter.

The clean way to do this would be to connect the power cable to a 12 volt cigarette lighter style outlet.

How long you can run the television depends on a number of factors...the size of your battery bank, the amount of power the TV draws and the load that is already on your house bank. If you are running down your start battery then consider isolating your start battery from your house batteries.
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Old 24-01-2011, 11:31   #3
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I see that you're going with a 13" screen. Have you considered a laptop plugged into an inverter? Very low draw and more flexible.

Good luck!
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Old 24-01-2011, 11:34   #4
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It need not be 12V to run off of your 12V system, although Target has a couple that are made to plug directly into a car cigarette lighter plug, and ARE for 12V. These could be hard wired if desired, just keep the far end of the wire that goes into the TV, (center+).

Many small 13" TVs come with a small black box that plugs into the 120V AC outlet. This converts the house AC to a lower DC current. Just look at "power out" on the boxe's fine print. If it is not already 12V DC, (which can hook directly to the boat's system), it mat say: "power out 18 V DC".

BINGO! Go on the web and purchase a converter box like those generally used to operate your LapTop computer from the car or RV. The plug for your TV is chosen to match up with the TV, and the other end has a Cigarete lighter plug. This can be hardwired into the boat if desired. This way you convert your 12V DC boat's power to 18 V or sometimes 19V DC, that the TV actually runs on. (It is also written near the TV's plug in).

This is 100% more energy efficient than using the boat's inverter and operateing the TV off of 120V AC! I have compaired, and the above set up is definetly the way to go. It also applies to computers, printers, etc, that have an AC black bok that plugs into the wall. Look and see what the device REALLY runs on. If you can supply that with a DC to DC booster, rather than turning on the boat's AC to DC inverter, you will come out WAY ahead.

Just make sure when shopping for these 12V DC to X DC converter patch cord devices, that they are designed for that operating amperage as well. There are hundreds of choices for these in online catalogs... usually under computer power supplies...

Hope this helps,
Mark
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Old 24-01-2011, 11:48   #5
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Thanks everyone for your input.

This tv comes with a small black box that converts the 120 down to 12v. If I am right about this, I should be able to cut the power cord, discard the black box and hardwire the power cord directly into the electrical panel.

This this seem reasonable?

Also, how do I know which of the two wires on the power cord is the positive and which is the negative?

thanks,
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Old 24-01-2011, 11:58   #6
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Quote:
Originally Posted by lake norman 285 View Post
This seem reasonable?
Probably. Make sure it is DC out and not AC. It may have a graphic instead of saying AC or DC - the one with straight lines is DC and the one with a squiggle is AC.
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Old 24-01-2011, 12:01   #7
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Yes, cut off the black box and wire to your DC panel. When you cut the wires you will probably see that one is different- maybe ribbed or maybe red inside. Then plug the black box into the wall and use a DC voltmeter to determine which one is positive. Then on the TV side, wire that one to pos on your DC panel.

If you are wiring to a 10-15 amp breaker then you are probably (I say probably because it depends on the size of the wire to the TV) ok without a fuse. If you are wiring to the main breaker or directly to your battery, install a 5 amp fuse near the breaker/battery.

Small LCD TVs pull about 3-4 amps DC and the DVD player about 3 amps DC. Divide that into your battery capacity to get maximum expected life, but don't routinely discharge more than 50% for best battery life.

Last year I bought an Insignia 23" high definition 120V/12V TV from Best Buy. It cost about $250.

David
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Old 24-01-2011, 12:40   #8
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Before cutting the cable, plug the converter box in the wall. Use a voltmeter to find which is positive and negative on the plug that would go into the TV. Cut the wire (unplug first). Now use the ohmeter to find which wire is a short to which part of the plug.

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Originally Posted by lake norman 285 View Post
Thanks everyone for your input.

This tv comes with a small black box that converts the 120 down to 12v. If I am right about this, I should be able to cut the power cord, discard the black box and hardwire the power cord directly into the electrical panel.

This this seem reasonable?

Also, how do I know which of the two wires on the power cord is the positive and which is the negative?

thanks,
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Old 24-01-2011, 13:18   #9
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Just a thought. If you got 3 sets of 6 volt batteries say to a scooter.( I`ve got them on eBay cheep ) and use them in sets of 3@18 volts if that is what you need? then you will have 2 independent power sources of power for the tv that the kids can abuse and can be recharged as 6, 12,or 24v at a time when you are making power.
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Old 24-01-2011, 13:56   #10
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Screen brightness has a significant bearing on current draw, i.e. brightness up, power up. Use the lowest picture brightness you actually need for the ambient light.
If you want to see what I mean, look at your amp monitor while turning up the picture control.
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Old 24-01-2011, 13:57   #11
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Cigarette lighter plug meltdown...

I put in a 22" LCD a while ago. The above advice about double (or more often) checking the polarity of the power supply is sound.

The only problem I had was that the cigarette lighter plug that came with the TV melted in the socket. I gave up on it and just hard wired it in.

The only other cautions that I can think of are to make sure that water won't drip on it, and to carefully check where it is going to be put. I put mine in the wrong place and had to move it. The bulkhead in the main cabin seems to be a fairly universal mounting place.

You'll also need a fairly decent aerial. I went with a Shakespeare one, but while I was fiddling, trying to get it to work (gain up too high...) I used some rabbits ears outside the hatch and that sort of worked.
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Old 24-01-2011, 14:07   #12
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On Antares we have a 17" Viewsonic that runs off a cigarette pack sized inverter. It draws only 3 amps. We use the HDMI output from the laptop to play DVD through the tv. We can also use the audio 3.5 headphone output to run the audio to the stereo for "suround sound" effect. I installed a "Hoop" style antenna and get HDTV. We even get 4 channels here in the Bahamas. You do not need a 12v unit.
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Old 24-01-2011, 14:51   #13
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would reccomend keeeping the power pack and cable for use in marinas or off a small generator,radio shack or equivalent sell blank 12 connectors,normaly inside hole is pos and outer surface neg.
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Old 24-01-2011, 15:42   #14
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I have that exact tv I cut the cord and wired it into my panel I am happy with it and also connected the power wire from the antenna amp in the same circut
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Old 24-01-2011, 16:02   #15
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Originally Posted by lake norman 285 View Post
Thanks everyone for your input.

This tv comes with a small black box that converts the 120 down to 12v. If I am right about this, I should be able to cut the power cord, discard the black box and hardwire the power cord directly into the electrical panel.

This this seem reasonable?

Also, how do I know which of the two wires on the power cord is the positive and which is the negative?

thanks,
I did this same thing several yrs ago with a 12" Sharp TV. Instead of cutting the power cord and ruining it, I just went to Radio Shack and bought the correct jack, 2 for $1, and hardwired it with an inline fuse, saving the original power cord to use later on if I want to use the TV elsewhere.
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