A 600mA universal adapter can output 864mA??

Discussion in 'General Electronics Chat' started by impaJah, Aug 3, 2012.

  1. impaJah

    Thread Starter New Member

    Aug 2, 2012
    I just got done testing to see if my 600mA universal adapter would output more than 600mA. To do this I hooked it up to 12 39Ω resistors in parallel. I had theorized that when I hooked my meter into the circuit between one of the resistors that there would only be about 60mA going through it instead of the 75mA that ohms law predicted. Well 75mA is what it read across the board with a grand total of 864mA outputted by the adapter.

    Do I not understand what a 600mA adapter means? I thought it could only output 600mA max?? Is this a flaw in the design? What's going on here? :confused:
  2. #12


    Nov 30, 2010
    You are suffering from extra quality. New engineers are being trained even now to remove this defect from future designs. The label, "600ma" means the device is only guaranteed to provide 600 ma without sustaining damage. If this output continues without smoking you will have to conclude that you received a bad device.
  3. MrChips


    Oct 2, 2009
    An adapter should have both a voltage and current rating.
    Hence if an unregulated adapter is rated for 12V @ 600mA,
    typically it may output 15V @ 0mA and the output voltage will progressively fall as more current is drawn. Hence it is very possible that it may output 800mA @ say 8 or 10V.
  4. impaJah

    Thread Starter New Member

    Aug 2, 2012
    Thanks guys, very informative!!!!!! I know not to fully trust those ratings now!!!!!!
  5. crutschow


    Mar 14, 2008
    It's not a matter of trust so much as it is a matter of design margin. Normally a well designed electronic device will deliver more than it's rating limits to insure that all devices at their tolerance limits will meet the spec. So a typical device may deliver somewhat more than its spec limit but you may damage the device if you continue to operate it above that limit.