IEEE 1394 - Taking a voltage reading

[OnePostWonder]

How do I accomplish this? I'm trying to take a voltage reading for the IEEE 1394 headers on my motherboard. I'll be using this digital multimeter. To take this reading, should I set it to 20v?

Using this as a reference: VIA 1394 brochure

It seems as if I should be able to take the positive to the white (volt. +) and the negative to the black (volt. -). I could be totally off, hence my asking here. I know for certain there are electronics wizards here!

Another question I'll inevitably be asking is: can I take this reading with the PC powered on? Or is it possible (and maybe safer) to take the reading with the power supply on and the computer powered off.

The reason I'm going about it in this way is because the only Firewire device I have around (that I'm aware of) is an old camcorder that doesn't have current enough drivers.

Thanks in advance!

[Hellraiser1981]

If your MB has a dc-dc converter to step up the voltage the white wire will read +30. You will have to have the pc powered on, but be careful not to short it to anything.
If the MB does not have a step-up converter then only twisted-pair signal wires are available and will probably read nothing on the DMM.

[OnePostWonder]

Originally Posted by Hellraiser1981

If your MB has a dc-dc converter to step up the voltage the white wire will read +30. You will have to have the pc powered on, but be careful not to short it to anything.
If the MB does not have a step-up converter then only twisted-pair signal wires are available and will probably read nothing on the DMM.

Hey, thanks for your reply. I edited the original post to actually contain proper links. Sorry if that screwed anyone up.

So what am I setting the multimeter to, and am I touching the negative to the case and the positive to the white wire?

[Hellraiser1981]

Depends on the meter. Use a setting for 30 or more volts. Higher ranges only lose precision.
You can use the case for ground.
Why do you need to test the port? Not working or something??

[OnePostWonder]

Originally Posted by Hellraiser1981

Depends on the meter. Use a setting for 30 or more volts. Higher ranges only lose precision.
You can use the case for ground.
Why do you need to test the port? Not working or something??

Yeah, it's not working as far as I can tell. As I said in the original post, I'm very limited in firewire devices, but the ones I do have that I'd like to work seem to be not picking up. I just want to make sure everything is savvy (plus I really enjoy learning these kinds of things).