Doubt before meassuring voltages with multimeter: Pc on or off?

Hi all
I have got a multimeter and before going measuring the real tension of +5 V line I'd like to ask you one thing.
Can I do it with the computer on, by taking the tension in a Molex (red and black cables)? Or the Pc must be neccesarily off, and jump the PSU so that it starts (only PSU)?

If I you can do with the whole PC on ...Won´t the PC turned off when connecting the multimeter probe in the Molex?
I say this because my motherboard ASUS P5Q SE sometimes has shutted down when connecting a DVD player to the Molex with the computer on.

Thank you very much
7 answers Last reply
More about doubt meassuring voltages multimeter
  1. There is a difference to plugging in a DVD drive (should not be done with it on) and measure the voltage. It is safe to measure with it on.
  2. Thank you rolli59 for your help: i will do with the pc on

    Another question please: what connector would you choose to test +5V?
    An unused Molex? or the main connector to the mother board (EATXPWR)?
    This later, with the Pc on, I supouse I can connect the probe with EATXPWR by "touching" the upper side of the connector (where cables are inserted)

    Thanks
  3. You can get your 12volt and 5 volt out of the same molex, yellow and black 12volts, red and black 5volts. http://www.playtool.com/pages/psuconnectors/connectors.html
  4. Just a worry note, you say you connect the dvd to the molex when your pc is on?
    aside from usb devices or hotswap hard drives, you should never add or remove a pc component whilst the unit is powered on, your lucky you havent fried yourself or your pc :)
    Moto
  5. Thanks all
    I shall never connect again any internal device with the pc on.

    BTW I have used multimeter, and verified that ASUS Probe II and BIos have incorrect voltages.
    Multimeter says everything is ok. I tested it with the PC on, in a Molex, and everything has gone alright.

    Thanks again for your guidance
  6. Glad you got sorted ok man
    Moto
  7. Be very careful in using your multimeter. I use a a tester with little crooked tip so it could grip the wires securely when measuring and I have an acrylic assembly so I can see the in and out of my rig - an insurance so the rig won't move when it is turn on.
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