Converting Small TV to 12 volts

[Paradocks]

I have a Sharp 13" tv and it has a 115 volt wire with a converter block.
I want to cut off the block and wire it direct. The wire has a center insulated wire and is surrounded by a wrapped silver wire.
I have assumed the center insulated wire is postive. I have completed the wiring and I get a power light on but nothing else on the screen comes on. It does work with 115 volts.
I know there is a previous thread about this with Mark Johnson but I can not find any updates as to whether it works.
Can any one shed any light on this?

[sarafina]

oh, I want to know about this as well! We have the same tv and I have been thinking about the possibility of doing this.

[motion30]

I have wired several , no problem The center is usually positive best to check with ohm meter

[Badsanta]

what does the power converter block reduce it too. It may not be 12 volt. if its not printed on it you could plug it in and put a meter on it.

[Paradocks]

It is reduced to 12 volts. The amps are 5.?

[ausaviator]

Check the back of the TV for the correct voltage and refer to the guide on the Internet if required. The centre wire will be positive.

[sarafina]

So if the voltage was right and the amps were within parameters then you could just hard wire the TV into the electrical harness? Or would it be better to put a plug on it and install a socket?

Will this work with lights that have converters as well?

[ausaviator]

A socket would be a good idea particularly if you wanted to move it or remove it in a hurry. If he lights are 12 volts then sure! Some vessels only have 12 volts across the board after all.

[ozskipper]

I am confused. What do you mean by converter block? A transformer? If so, is it a 12 volt transformer? Or are you confusing it for a filter of sorts.

BUT ,,,and here's the but. The wire you are talking about sounds like the RF cable. Single copper strand with insulation and a copper sheath. Which is by no means a power cable. A photo of the cable might just save you a fire.

[ausaviator]

After checking the power specifications you can "probably" walk into an electrical store and pay less than $10 for a cigarette lighter cord and plug it straight in, assuming you have a lighter socket. You can get cords with different sized plugs on the end or alternatively attach one yourself if you are confident.

The braided style cord is probably perfectly adequate for use in 12 volts to a TV.

[SunDevil]

Power Supply Units Abbreviations and Symbols

I'm assuming that you have a power brick that is an 120V AC to 12V DC converter. And I'm assuming that there is a barrel plug that gets plugged into it from the TV.

It should have a polarity diagram on it. And it should say that it is outputting 12 V (not 18V) Or the wires might be marked + 12 and G.

Also, you should look at getting a fuse (there is one built into these plugs)
http://www.1stincity.com/3311-8382-l...ug-lcr015u.jpg

And mounting an outlet in the wall is a good idea.

[noelex 77]

I have done this with a LED monitor and other appliances. It saves power and is easier and neater than running the inverter.
The only problem is that you are running the tv on up to 14.5v or so with the charging sources on. Most appliances will cope with this higher voltage without any problems, but not all.
In the end you have to take a chance. One usefull test you can do is measure the existing transformer voltage. If the appliance has an unregulated transformer it will measure about 15v dc. With this type a transformer once the load current is applied the voltage will drop to 12v, but at least you know the appliance will accept an instantaneous higher voltage. Appliance with this type of transformer are more likely to tolerate the higher voltage from a boat supply.
The second type of transformer is a regulated one. This will measure 12v with a multimeter and will maintain that voltage. The risk of running an appliance with this type of transformer on the boat battery is higher.
A simple trick is put a diode in series. This will drop the voltage by about 0.6v and moves it into the better range. Low voltage is generally safer, but with with flattish batteries or other high loads the appliance could be running on on only 11v. The diode is generally safer, but I would not use it if you poor wiring (with voltage drop already incorporated), or if running high loads like microwave at the same time as using the appliance. So a diode is a good idea, but there are no guarantees.
you can incorporate a regulation circuit, but the simple ones drop some voltage which means you can have too little volts when not charging. More complex circuits can maintain a constant 12v, but the power savings are less and most people would simply use an inverter if this is required.

Running directly from 12v is generally OK, but be aware you are taking a risk. I will only do it with an appliance that is cheap enough to replace without too many regrets. A diode is safer, particulary if the transformer is regulated, without it try not to run the appliance when the battery voltage is high.

[goboatingnow]

Originally Posted by noelex 77

I have done this with a LED monitor and other appliances. It saves power and is easier and neater than running the inverter.
The only problem is that you are running the tv on up to 14.5v or so with the charging sources on. Most appliances will cope with this higher voltage without any problems, but not all.
In the end you have to take a chance. One usefull test you can do is measure the existing transformer voltage. If the appliance has an unregulated transformer it will measure about 15v dc. With this type a transformer once the load current is applied the voltage will drop to 12v, but at least you know the appliance will accept an instantaneous higher voltage. Appliance with this type of transformer are more likely to tolerate the higher voltage from a boat supply.
The second type of transformer is a regulated one. This will measure 12v with a multimeter and will maintain that voltage. The risk of running an appliance with this type of transformer on the boat battery is higher.
A simple trick is put a diode in series. This will drop the voltage by about 0.6v and moves it into the better range. Low voltage is generally safer, but with with flattish batteries or other high loads the appliance could be running on on only 11v. The diode is generally safer, but I would not use it if you poor wiring (with voltage drop already incorporated), or if running high loads like microwave at the same time as using the appliance. So a diode is a good idea, but there are no guarantees.
you can incorporate a regulation circuit, but the simple ones drop some voltage which means you can have too little volts when not charging. More complex circuits can maintain a constant 12v, but the power savings are less and most people would simply use an inverter if this is required.

Running directly from 12v is generally OK, but be aware you are taking a risk. I will only do it with an appliance that is cheap enough to replace without too many regrets. A diode is safer, particulary if the transformer is regulated, without it try not to run the appliance when the battery voltage is high.

LDO ( low dropout regulators) ICs are two a penny, techies could rig up one with a couple of caps etc.

Dave

[goboatingnow]

Originally Posted by ozskipper

I am confused. What do you mean by converter block? A transformer? If so, is it a 12 volt transformer? Or are you confusing it for a filter of sorts.

BUT ,,,and here's the but. The wire you are talking about sounds like the RF cable. Single copper strand with insulation and a copper sheath. Which is by no means a power cable. A photo of the cable might just save you a fire.

What the Op mentions is a typical switch mode buck converter that's used to drop the 120 to 12 and rectify it. The cable he describes is not uncommon. There no requirement for a power cable not to be arranged co-axially .

Dave

[Paradocks]

Thanks for all the info. I tried a direct 4' cigerette lighter plug and cord yesterday and it worked fine. I narrowed everything down to a power drop running 15' back to the breaker area. I now have to use a meter and find a good power supply. This might mean running to the battery switch. I will not be back to the boat for two weeks but I will try that then. The power brick and TV both say 12 volts.