general hardware question

Hi,
I got a question, when you install hardware I always have been taught to just touch the power supply and use a grounding wrist strap clampped on the drive cage and to have the power supply off and unplugged when installing anyhardware. But Crucial's installation instructions say that you should leave the power supply plugged in and the system off when installing anything to the mobo. I have heard both so which one is rightor is this a grey area?

Thanks

 

Whenever you are working on a computer doing anything but replacing or working on the power supply the machine should remain plugged in with the power off.
That way it remains grounded. If the power supply has a on/off switch on the back turn it off, Or turn off the power strip feeding the computer.
I know this because I got the question wrong on my A+ test

 

The newer ATX systems should be unplugged from the incoming AC power before working on anything inside the case. The motherboards in these systems are constantly powered, even when the system is shut down. Most newer motherboards even have a light on them to indicate when they are powered, and the manuals warn to not connect/disconnect anything while that light is on. It's possible to ground the case after unplugging the incoming AC power line by using a ground strap connected to the case and a good ground source.

A quote from the manual for the Abit TH7II that I working with right now:

http://202.168.194.181/abit/upload/fae/th7ii-e.pdf

The old AT style power supplies were different. If you turned off the power supply, all power to the motherboard was shut off.

Edit:

The link above will start downloading the manual in .pdf format - it's just under 4MB and 96 pages.

 

Cliffh,
I agree with you, but if you answer that way on the A+ exam you will be incorrect.
If you throw the switch on the back of the power supply it cuts the 110 volt hot wire (black) and leaves the Neutral (white) and ground (green) connected which will drain all ESD to ground.

Take apart a power supply (unpluged ) and look at the 110 volt side and you will see. I argued with the instructor but to no avail, he proved me wrong.

The motherboard manufacturer probably states the info that way for liabuility reasons.

One more thing and I dont know this for a fact but the power supply is full of capcitors that would stay charged if the neutral was cut by unpluging the power chord.

Let me know what you think,
Scott

 

I have two computers that do not have a power switch that cuts the power. Only an electronic switch that toggles the rest of the power supply via the micro.

The only way to unpower and keep ground is with an external power strip or as suggested unplug and then ground strap.

Where I retired from, we had ground straps on the bench for that reason. The earlier computers did have a large mechanical switch.

So, I think you are both right and together are REALLY right.

 

Well, what I have been doing I unplug the system totally and use a grounding wrist strap and plug that strip into the drive cage and then touch the power supply... will this remove the static electricity from me?

Thanks,
Mike

 

The best procedure in all circumstances is to disconnect the power cord and attach a ground strap to the chassis. Then attach your wrist grounding strap to the chassis. Then as an additional precaution (redundant) touch the chassis before touching any components.

I used to use an old line cord with the current carrying conductors removed and leaving only the green ground conductor intact. It makes for an excellent ground without having the hazard of working on equipment with the possibility of coming into contact with lethal voltage. It also provides a bleed for any static electricity that your body may have.

Trust me, this method will fly with anyone that knows his ionized charge from his electron flow.

BTW, Wrist grounding straps are extremely dangerous if you are working on a device that is plugged in to the power source. You are betting your life on a simple on/off switch that costs less than 10 cents to manufacture. From that standpoint, you would be better of NOT being grounded. You can touch an energize wire and suffer no shock if you are insulated from all ground sources. Power line maintenance personel often come in contact with extremely high voltages accidentally but the "Hot Stick" they are in has a fiberglass boom and keep the ground path from happening. When you put that ground strap on your wrist, you have fulfilled half the requirement for an electrical circuit. Do yourself a favor, keep the other half of the requirement disconnected and out of the immediate area.

The old rule was, if working on live equipment, keep one hand in your pocket at all times. I'll go that one farther, keep both hands in your pocket unless the thing is unplugged.

Stay Safe! There are careless electricians and there are old electricians, but there are few old careless electricians.