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

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November 1, 2010 7:54:44 PM

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
a c 715 ) Power supply
November 1, 2010 8:19:10 PM

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.
November 1, 2010 8:56:09 PM

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
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a c 104 ) Power supply
November 2, 2010 2:20:07 PM

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
November 2, 2010 8:02:19 PM

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
a c 104 ) Power supply
November 3, 2010 6:49:36 AM

Glad you got sorted ok man
Moto
November 3, 2010 9:53:16 AM

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.
!