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I wish to remove some RAM from a PC, as memtest suggests this is the cause of some crashes.

So I have bought an anti-static wrist strap, and have carefully read some online instructions. These can be summarised as:

  1. Leave PC plugged in, but turned off at the mains
  2. Connect strap to wrist
  3. Connect crocodile clip to unpainted part of PC chassis

It all sounded so easy, but the PC case is a Xigmatek Midgard, and it seems to be painted in its entirety. I can't see any bare metal inside it at all.

Where should I attach the crocodile clip, to ensure I've discharged any static electricity?

This is what the PC looks like inside:

enter image description here

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2 Answers

up vote 3 down vote accepted

Power supply's cover is a good place. You only want a good ground connection, and power supply is always grounded.

Moreover, ESD protection is a complex issue... What you need to prevent is a electrical charge difference between your body, tools, etc., and ESD-sensitive equipment. So, the procedure should be something like this:

  1. Bring your body to the same electrical potential as your computer's ground. E.g. connect your wrist wrap to your computer's chassis, or any other metal part connected to the ground.

  2. Keep memory sticks inside their anti-static pouches. Touch the inside surface of the pouch, then get the sticks out, and holding them between your fingers on the edges, e.g. not touching the contacts or anything on the their PCB, place them in their slots on the motherboard. Then push them on their top till the latches engage.

If you cannot find a non-painted place on your power supply (not even a screw or something else to clip your ESD strap to), you can connect your ESD strap to any black wire coming out of your power supply (it is a grounded wire). Bend some paperclip into a springy loop, insert into any connector's black wire socket, and you have a good ground.

Important: What you need is a same electrical potential between your body and your equipment. You don't need to be grounded, and your equipment does not need to be grounded. So you can completely disconnect your computer from the mains. I always do that, as an extra precaution: one glance can always tell you if your equipment is under power or not.

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Thanks for the reply. In the picture, the power supply is bottom left, and is completely covered in black paint too. Or have I misunderstood? –  Clare Macrae Dec 21 '11 at 19:32
    
Is there any static electricity on the British Isles? ;-) I always remove a mobo from a case when installing RAM and use Anti-Static Polyethylene Foam. –  Aki Dec 21 '11 at 19:50
    
@ClareMacrae: you're right, it's a power supply. It is hard to see if it is painted completely. I'll amend my answer. –  haimg Dec 21 '11 at 20:01
    
To anyone else puzzled by @Aki's answer, wikipedia tells me that a 'mobo' is a casually shortened motherboard :-) –  Clare Macrae Dec 21 '11 at 20:33
    
Chances are you can probably conduct even through the painted components. Probably anecdotal, but in reality I do hundreds of RAM swaps a year and I rarely if ever use an anti-ESD strap. Do the replacement on a hard surface (i.e. NOT carpet), discharge any ESD from your body on something grounded (PC case, metal surface, buddy, etc.), and then seat the memory. –  Garrett Dec 21 '11 at 20:53
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Current should travel without issue through a layer of paint that thin. Any resistive or non-conductive material (paint, paper, air, etc) has a given level of resistance, after which point current will travel across or through it.

Air is a resistor, but the charges built up in the atmosphere during a thunderstorm can become high enough to overcome the resistance of the air gap and the result is lightning. A shock on a door knob on a cold dry say when you're walking on a synthetic fiber carpet is the same thing, the smaller air gap just before you touch the door is overcome by the charges built up in your bode.

The paint covering machines like this will only be slightly resistive, if at all. They may even be impregnated with metal particles so that they are conductive, rather than resistive. It will only take a very small differential between the energy in the clip (your body) and the chassis to bridge the gap of the paint and establish a ground connection. The direct connection between your body and the group strap and between the clip and the chassis will prevent any sparking when any transference takes place.

However, all that being said, the ground strap will only work connected to the computer when the computer is plugged in, and you don't want to work on a computer that is plugged in. The better thing is to connect the ground strap to a completely different item that is grounded (plugged in with a grounded plug).

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Does this mean that the Lindy instructions (linked in the question) are wrong to say to leave the computer plugged in but turned off at the mains/wall? It claims that doing this does ground the chassis OK. –  Clare Macrae Dec 21 '11 at 19:49
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That would work in a pinch. But do you trust the off switch on the PSU? Generally you want the computer unplugged and you want to be grounded elsewhere. –  music2myear Dec 21 '11 at 19:53
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@music2myear: Your answer is dangerously wrong. If you're grounded and your equipment is not, there is a chance of electrical potential between you two. You don't need to have a ground, you need same electrical potential. Second, ESD strap already have 1Mohm resistor inside, add to this paint resistance, and your static charge may drain too slowly to prevent ESD damage. –  haimg Dec 21 '11 at 20:00
    
@haimg: which is why you grab the machine chassis with your bare hand in order to equalize any electrical charges between you and the device prior to beginning work. Charge equalized equals minimal chance that sufficient buildup will occur during work as your many small touches whisks continually work to equalize the charge differential. –  music2myear Dec 21 '11 at 20:05
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@music2myear: Why bother with the ESD strap then? The point of a strap is to have same potential at all times while you work. Dangerous static charge levels can build up in seconds, with the right clothing, especially in dry winter air. And this person also has fully painted case, therefore brief touch may not be enough. –  haimg Dec 21 '11 at 20:11
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