mains to 12v advice please

Discussion in 'Tech/Mech General' started by greyman1, Aug 21, 2013.

  1. greyman1

    greyman1 Read Only Funster

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    hi guys , i have tried to adapt my mains elec tv/combo [50w] to run direct from 12v by replacing the black box mains 12v step down lead to one with a cigarette type connector direct to the 12v supply socket so that i can use the tv when not on ehu but i am having no success ! the 2amp fuse that came with the connector blew immediately, i then tried a 5amp fuse,this lasted about 10mins then blew . i think the actual fuse in the monoblock unit for the 12v supply is 10amp so do i have to do away with these inline fuses and just rely on that ? the problem with this though, is when i pulled the 10 amp fuse to double check it was 10 amp the boiler dump switch operated and dropped all the water out of the boiler ! which wouldnt be ideal when parked up on a aire etc ! cheers garry
     
  2. tonka

    tonka Funster Life Member

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    Strange.. 50w is just over 4 amps so in theory a 5 amp should be ok..
    I would not take out the inline fuse it's there for a reason, TV although stated as 50w may in fact draw more.. If it was me I would look to try a 7.5amp fuse if you can get one. Also remember some cigarette sockets can be low powered and get warm very fast, giving further issues...

    Good luck..
     
  3. rainbow chasers

    rainbow chasers Read Only Funster

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    Just to recap.

    Your tv is 12v, stepped down from 240 mains through the mains cable which has a black box halfway down.

    You have replaced this with a voltage stabiliser (such as amperor) and it is popping fuse on start up.

    NEVER replace fuses with larger ones, you will damage the equipment, wiring on your van or it may just burn to the ground.

    Check that no more than 3 items are running from this supply. Check the voltage stabiliser to ensure you are not overloading it - I don't know what make you have, but check its' max capacity just to rule out. Some TV's require a higher output to start up.

    Then look at you 12v supply - this is more than likely the culprit, and is shorting. check wire are right way around and secure with no chaffing. If you have a lighter socket with a couple of crocodile clips handy, attach that direct to the battery, and plug in the stabiliser and see if this makes a difference. If it runs fine, there is definitely an issue with the 12v wiring.
     
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  4. Sallytrafic

    Sallytrafic Read Only Funster

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    One other thing to consider is that the step down transformer may have produced a regulated 12V whereas the 12V in your van might be over 14V whilst charging. When you say TV/combo what do you mean, what else is there besides a TV?
    Anyhow I would use a slow to blow 5A fuse max.
    BTW very surprised that the heater is on the same circuit as the 12V socket
    Hope this helps
     
  5. greyman1

    greyman1 Read Only Funster

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    thanks guys your helpfull replies have give me some food for thought ! 1st by tv combo i meant tv/dvd . 2nd the 12v lead i am using just goes straight from the 12v supply socket to the tv and does not go via a voltage thingy ! [according to previous advice i was given on here this set up should work but might shorten the life of the tv eventually. as i am going to replace the tv at xmas i thought it was worth a try as is !!] what has really made me think though, is that as the 12v supply is coming from my fully charged 110amp leisure battery, which actually shows almost 14v on the battery test gauge above the door AND I CANT NOW BE 100% SURE THAT I DISCONNECTED THE EHU CABLE [which inc on board charger]when i was trying it on 12v DOOOHHH !!!! i am now thinkiing this is more than likely the culprit . i will try it all again connected direct to leisure batt via croc clips and with no ehu on !!! cheers again garry
     
  6. Scotties

    Scotties Funster Life Member

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    Most likely reversed polarity at 12 v end:Sad:
     
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  7. hilldweller

    hilldweller Funster Life Member

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    Have you got an ammeter ? Only a tenner or so. Connect via this and see what is really happening.

    What TV ?

    I've done this with a new Kogan TV and it's worked over a year now.
     
  8. rainbow chasers

    rainbow chasers Read Only Funster

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    After the last Transit I had in nothing surpises me anymore! Fuel pump ran off the rear light circuit.....:Doh:
     
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