Tv 12v power problem.

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Post by splashmac on Fri Jul 27, 2018 2:24 pm

My tv works fine on ehu and had also been used on 12v.
But the no 9 fuse has blown on the Sargent when I plugged in the tv on 12v. 
This circuit also feeds my Maxview Sat dome. 
I thought that I had found the problem as the 12v connection was through a connector block 
but when I removed the tape I found the wires had come loose and must have blown the fuse.[You must be registered and logged in to see this link.]
Two wires, one red and one white each with a screening mesh round it like on an aerial cable.
I connected red to red and white to white on the connector block and ignored the 'mesh. but fuse still blows.
Everything is fine on ehu but when I try the 12v with tv the fuse blows again.
I do not have a clue how the wires connect, is the screening some form of earth?
 I have attached some pics and as you can see the wiring looks in a mess. 
The other taped connection is the power to the satellite selector box. 
AS Gloucester 2010 model. Regards Keith.
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Post by brodco on Sat Jul 28, 2018 4:50 pm

Hi wave

Unfortunately I have no idea how your system is wired but unless someone with exactly the same system chips in we’ll need to see if we can work it out.

Firstly I think a bit more clarity is needed. confused3

Has the TV got a satellite input or are you using a receiver “box”?

What is the make and model of the TV?

Where does the plug in the picture normally go?  It looks to be a normal TV aerial cable, I an only see a white inner and a screen (braid).

I suggest as a first test completely disconnect the TV and the satellite system, then see if the fuse still blows.

Assuming it doesn’t disconnect all the cables from the TV (apart from the 12V power) connect the TV to 12V and see if the TV powers up on its own.

The next step will depend on the results.

Brod
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Post by splashmac on Sat Jul 28, 2018 6:26 pm

Hi, hope this helps.
Maybe more background first. I found that the tv would not work on hookup and then remembered that I had taken the 13amp fuse out to help someone and had not replaced it! Later when fuse replaced and still on hookup I noticed that the sat system was down and found the 10amp fuse had blown. I had been routing around in the TV / Sat  control area as there were quite a few wires and I had changed a faulty scart lead from sat box to tv (no HDMI). I thought that I must have disturbed something.  As I had found some cobbled together wiring I undid the taped up 12v feed to find the wires hanging out of the connector block but not readily identifiable. I separated the 12v connection, replaced the 10 amp fuse and sat system restored. then the mains connection to TV worked fine.
To answer your questions:
1. Maxview satellite dome with selector box and control box with remote control.
Pictures attached.
2. TV is a Manta 19" which operates on mains and 12v. Connector being the same in each case as shown in first posted picture.
3. The plug in the picture goes into the TV and in this case is the 12v one. As I mentioned above the mains connection is a similar plug and goes into the same female connection on the TV.
4. The wires which carry the 12v feed comprise one white and one red, each having a copper braiding/screening round it. The same goes for the short length with the plug.
5 I have previously tested as you advise and fuse is okay. It only blows when the wiring in question is used with the connector block. The issue is definitely with how the 12v feed is wired.  I have also tested with a cable into an existing 12v socket in the van and TV and sat system work fine.[You must be registered and logged in to see this link.]
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Regards Keith
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Post by brodco on Sat Jul 28, 2018 7:17 pm

Hi wave

Humm scratch head

Is this the satellite dome?

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Is this the TV?

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Sorry about all the questions - just trying to understand what’s going on.

Brod
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Post by brodco on Sun Jul 29, 2018 10:57 am

Hi wave

Had a thunk!  hugegrins

Red white and braid suggests and audio cable (left, right and earth) rather than a power cable although it’s possible someone used an audio cable as a power cable- a bit odd though.

I’m still not quite clear what you’re connecting to what but the plug in the picture only appears to have two connections which is what you would expect for a power plug. If that’s not the case can you get a close up picture showing the third connection.

The white will almost certainly be the inner positive pin and the braid will be outside earth connection. It’s very common for the braid to be negative.

Now to find out where the 12V is:

To save time, not to mention fuses, I suggest using a multimeter, i.e. measure between the red cable inner and braid, the white  cable inner and braid and red to white inners, or even better run a new cable back to the 12V source. If the meter is the wrong way round it will simply read ”- X.XX ”

Then switch the meter to Ohms and measure across the white inner braid of the plug it should read “OL” or at least very high. You can be almost certain that the positive needs connecting to the white inner and the negative to the braid. There may be some legend on the TV to confirm this. Occasionally the inner is negative but that is rare.

Brod
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Post by splashmac on Sun Jul 29, 2018 1:12 pm

Will get a multimeter and check. Yes to both the sat and tv links.Thanks
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