ATX POWER, Upgrading cards etc.

[Fluff]

When the machine is off. But the ATX power supply is still connected to the motherboard and the mains, the system is off.

Is it safe to change memory, and cards etc? Or do i have to unplug the PSU from the mains?

Peter

[az]

Just unplug it, you'll always be on the safe side then. Or switch the PSU off, if it has an own switch.

AZ

[UtwigMU]

Generally you need to unplug it or turn it off by button on PSU (as per ATX specs button is mandatory).

There is backup voltage provided for wake on lan or wake on ring.

Although I swapped cards a few times with PSU on and nothing happened, it should be still off.

[spadnos]

In fact, it's a good idea to unplug the supply, then press the normal power button - this discharges capacitors (both in the PSU and on the motherboard), and makes things even safer.

- Steve

[Jammrock]

Motherboards have a residual power going, even if the computer is "turned off", as the ATX standard has the motherboard controlling the power on/off function, instead of using a relay.

Thus it's always good practice to 1) unplug the power supply, 2) ground yourself (use a grounding strap if you got one, otherwise try and keep a hand touching the case at all times), and 3) never force anything into it's slot (which is a good idea for more than just computers).

Jammrock

Jammrock

[The PIT]

Yup what happened to the day when off was off.

[DGhost]

If you are really paranoid about it, unplug the power supply from the motherboard before installing cards or memory. the PSU will hold a charge for several hours unless you were to get inside it and discharge the capacitors by hand.

that being said, I have done enough work on computers while the PSU is switched on and plugged in (with the computer off, of course) that I don't have a problem doing it. as long as you are grounded, of course.

[The PIT]

Sure that wasn't the older type of motherboard???
Ever time I've forgotten to switch off the machin has always started booting when I pulled a card out.

[az]

You aren't grounded if you touch the case with the power cord unplugged, because the case won't be grounded anymore. Touch any metallic water installation (heating, tap...).

AZ

[Wombat]

Originally posted by az
You aren't grounded if you touch the case with the power cord unplugged, because the case won't be grounded anymore. Touch any metallic water installation (heating, tap...).

AZ

Even then you're not grounded correctly. If the case isn't grounded, or is grounded to something electrically distant from you, then you've got floating grounds or ground loops.

[Fluff]

So generally.. It's about as safe either way.

[az]

Best would probably be switching the PSU off if it has a dedicated real power switch, and grounding yourself to the case. (of course, when you suspect something is wrong with the computer or psu, better unplug it).

AZ

[Wombat]

Originally posted by Fluff
So generally.. It's about as safe either way.

Ground yourself to the case, and then the case to a true ground source.

[Mehen]

leave everything plugged in, including the power cord to the wall, just switch the powersupply off. That way everything is grounded, and the only thing you will damage is... you. What is more important: expensive hardware zapped or you gettin a little electrical burn and that awesome charged feeling?

[Greebe]

Hey I could chime in with yet another howto properly handle grounding safety (safely?