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ARCHIVED FORUM -- April 2007 to March 2012
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This is the first Archived Forum which was active between 17th April 2007 and 1st March February 2012

 

Latest post 04-09-2008 6:36 PM by The Stig - ver. 1.7. 7 replies.
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  • 04-09-2008 10:37 AM

    A shocking question

    Hi all:

     

    I have another project on the go that I will probabl get half way through and then not be bothered to finish it. Well at least whilst it holds my interest in will keep me out of trouble:

     

    What I am intending to do is get an old television of iconic "of its era" design - namely an old Ferguson from the 70s/80s or a Bakerlite model, remove the innards and put a stripped down PC with LCD screen, Freeview etc in it. Like a retro media centre.

    I am hoping to get most of the components from Freecycle.

     

    What I would like to know is, do LCD monitors/screens carry the same high voltages as CRTs? I think that I may actually have to take the LCD screen out of its casing to make it look/fit better inside the old TV case. However, I do not really want to get 240v through my hands.

     

    Has anyone on here tried something similar? I have heard of people doing it and was thus wondering what are the things to look out for are etc.

     

    Thanks

     

    Graham

  • 04-09-2008 12:09 PM In reply to

    • camshaft
    • Top 150 Contributor
    • Joined on 04-16-2007
    • Pennsylvania, USA
    • Posts 575
    • Founder

    Re: A shocking question

    Regardless of the voltage, if you unplug the set first, and wait for the caps to discharge, I really don't see how you'd get shocked by working on it.  LCD's use lower voltages, but the power supplies are typically located inside the housing, so there will still be 240v up until you get to the supply.
    -Austin (resident audiophile skeptic)
  • 04-09-2008 12:31 PM In reply to

    Re: A shocking question

    Hi:

     

    Thanks, how long should I wait for the CAPS to discharge? I have worked on PCs which obviously have CAPS on them and have never been shocked. Is it just a case of common sense - don't mess around with the power supply, don't mess around with it whilst switched on etc?

     

    Thanks

     

    Graham

  • 04-09-2008 2:06 PM In reply to

    • Alex
    • Top 25 Contributor
    • Joined on 04-16-2007
    • Bath & Cardiff, UK
    • Posts 2,990
    • Bronze Member

    Re: A shocking question

    The actual LCD element itself uses a 12v charge I believe, but this doesn't include the other components.

    Just to be safe, I'd wear rubber gloves and leave it unplugged from the mains to discharge for some time...

     Weekly top artists:                   

  • 04-09-2008 2:57 PM In reply to

    • Puncher
    • Top 10 Contributor
      Male
    • Joined on 03-27-2007
    • Nr. Durham, NE England.
    • Posts 9,588
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    Re: A shocking question

    LCD backlights use Inverters which electronically generate high frequency "mains-type" voltages. Normally, inside appliances, there is a rule that high voltage caps across the mains cord must discharge to less than 34V within one second but this doesn't apply to internal circuits and so caps can retain their charge for extraordinary lengths of time. The best plan is to discharge any suspect caps with a suitable resistance (do not short them with pliers etc). The circuit schematic is always the best indication of what is likely to need discharging - I suppose a rule would be "if you can't read the schematic - don't dabble". On the other hand if the appliance hasn't been powered up for a day there is little chance of anything retianing any hazardous voltages.

    Generally speaking, you aren't learning much if your lips are moving.

  • 04-09-2008 3:05 PM In reply to

    • camshaft
    • Top 150 Contributor
    • Joined on 04-16-2007
    • Pennsylvania, USA
    • Posts 575
    • Founder

    Re: A shocking question

    Yeah, assuming you're not in a rush, which you shouldn't be, just unplug the thing the day before you go to work on it.
    -Austin (resident audiophile skeptic)
  • 04-09-2008 5:22 PM In reply to

    Re: A shocking question

    I would talk to Richard about this  (a2bur) It sounds like one of his projects!!
  • 04-09-2008 6:36 PM In reply to

    Re: A shocking question

    When you take your LCD screen apart you will find, that it's housed in a metal box and as long as your on this side of it your OK Smile
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