Discussion in 'General Electronics Chat' started by Silva, May 13, 2007.

  1. Silva

    Thread Starter Member

    Apr 25, 2007
    Is it safe to connect electronic equipment in a transformer whose secondary is 140v ac since the equipment 120v ac?
  2. wireaddict

    Senior Member

    Nov 1, 2006
    If you're asking if it's safe to connect 120 VAC devices to 140 VAC, in most cases the answer is no; the current, power &, therefore, heat would exceed the device ratings & would shorten its life span. Most '120 VAC' devices are rated for about 110-125 V[AC].
  3. recca02

    Senior Member

    Apr 2, 2007
    like mr wire addict said,
    it may not be safe do do that,
    since giving any voltage higher than rated value will mean that circuit will
    draw more current than it can handle I=V/R
    so current in case of 140 volts will exceed that at 120 volts and excess current might damage the circuit.
  4. mozikluv

    AAC Fanatic!

    Jan 22, 2004

    am just curious, is that a specially wired step down transformer having a 140vac output?

  5. thingmaker3

    Retired Moderator

    May 16, 2005
    By Ohms Law, current would increase by 17%, therefore power dissipated would increase by 36%. Most things won't handle an extra 36%.
  6. Silva

    Thread Starter Member

    Apr 25, 2007
    Thanks for the advice, well the transformer that i'm talking about was from an old tube tv and i'm using it as an isolation bench transformer, to protect from the line service in between the 120v outlet and the tv sets i'm working on,so far did not cause any damage yet, but someone suggested that is too much voltage, i thought that since the i'm inputing 123vac and the secondary is 140v, the diference 17v would not make that much diference,since i'm not counting the load.I guess i have to find another tranformer of the same size same volts and connect it secondarys sides together as some one suggested as a home brew isolation bench tranformer. Thanks in advance. (forgive my bad writing)