YOU MISUNDERSTAND. IF no ground, the static discharge has NO place to go so you and the case are still at a difference of potential as no current will flow.
With all due respect, Sir, that is woefully incorrect and the source of your confusion. Please understand, I respect your 50 years, but I've been a degreed and certified electronics technician for Air Force air traffic control facilities and DoD secure networks since 1972 and have taught electronics, electronics safety, troubleshooting and repair, ESD, ESD control and ESD prevention.
I would ask, if the static charge does not go anywhere, what happens to it when you shuffle across the carpet and touch the door knob in a wooden door? By your statement above, all those 1000s of volts would still be there - stored somewhere, somehow in the door or door knob. Does that sound right? No, of course not. Door knobs and wooden doors are not capacitors. They are not batteries. They don't store electrical energy, they don't hold a charge. Doors and doorknobs are not wired to earth ground. So where does that energy go? It is converted and
discharged in the form of
heat - the mini-lightning bolt that is so destructive to sensitive devices.
If you touch an object - any object - or touch any two objects together, the "difference of potential"
between those two objects becomes zero volts - a "
common ground" is established between them.
That's the key!!! It does not matter if that common ground is 10,000 volts above Earth ground, or 10,000 feet above the Earth in the air. Once it is neutralized, the common ground prevents any difference from building and
there is no current flow between those two objects - again, the key, as there's nothing to discharge.
It does NOT matter, 1 iota, if there is no path to Earth ground when doing maintenance inside a computer (unless testing for live voltages). If that were the case, there would be no such thing as avionics, or even automotive electronics.
Once you have discharged yourself on the case with the PC plugged in, then you can unplug it and work safely.
Again, that is incorrect. As noted, simply moving in your clothes when pulling that plug
will knock loose free electrons, and start the process of building up a static charge in your body again. The problem with ESD sensitive devices is they can be destroyed by a discharge so small, humans are not even aware a discharge occurred. But it did. Humans don't see the spark and they don't hear the snap. This is why you must stay in frequent contact with the case so there is NO difference. With no difference, there can be no flow, or arcs.
Yes, the best solution to prevent any ESD problems is to use grounding straps to connect you, the bench, the computer, and the floor mat together creating a
"common" ground, then to a
certified "facility" ground (NEVER a wall outlet!). But most folks don't have properly wired, professional test benches in their homes, or certified grounds. Most people, sadly, just assume their wall outlet is properly wired and grounded and never even test the wiring in the outlet, or use a
AC Outlet/Ground Fault Indicator Tester.
The cases are all metal and you do NOT have to reach in to discharge any static electricity while the power cord is plugged in
Again, this is totally incorrect. First, you NEVER reach in
before discharging - you always discharge to bare metal first, then reach in. Second, it is not static in the computer you need to be worried about, it is static in your body! Third, the point of discharging your body to the case is so
you don't discharge your static charge through the ESD sensitive device, such as memory modules and the CPU.
And once again, NEVER - as in never-ever assume any power cable is safe. Never assume the ground wire in a power cable will protect you when there's deadly voltages running through the same 25 cent power cable! Additionally, never, as in NEVER EVER assume the wall outlet is properly connected to Earth ground.
WARNING!: MANY older homes and buildings only have two-conductor house wiring! Just because the outlet has been upgraded to accept a 3-prong plug does not mean the outlet housing/box is attached to a big fat copper ground wire, or that the copper ground wire goes to ground. Power cables are cheap, injected plastic molded devices designed to provide power. They are no substitute for a ground strap - a
safety device designed to save your life and protect equipment. I also note that using the power cord for ground assumes there is a good, tight, mechanical connection, with zero resistance, between the PSU housing and the PC case. Bad assumption.
While ESD (electro-static discharge - static shocks) have been around forever, an understanding of ESD is relatively new as vacuum tube technologies are much more immune to the effect. It is only when they started jamming 1000s of semi-conductors in to tiny integrated circuits, that where then being damaged by improper handling, did a full understanding of ESD come about.
I am NOT suggesting that the power cord remain plugged in when working on your PC although I do all the time and have for the last 50 years.
Then Sir, you have been risking death for 50 years. Power cords
IN NO WAY prevent static discharges building up in our bodies, nor do they prevent discharges from occurring, or doing damage. But more importantly, power cords should never be trusted to keep you from electrocution should the cord, or the $10 generic power supply, fail. That assumes the cord, PSU,outlet, and facility wiring are all correct. Should that power cord get yanked one too many times, you risk YOU being the direct path from 110VAC to ground!
Please don't become a statistic.
Common sense is still the best safety factor
No. Education is the best safety factor. Common sense can be deceiving and lead us astray.
if you don't know what you're doing, stay out of the equipment.
Now that I agree with. But sadly, dust does not heed that advice and users must periodically clean their computers of heat trapping dust. And to do that, they must understand ESD prevention.
I say again - anything that plugs into the wall can kill. We must not assume, or lead others to assume it is okay to put blind faith into a cheap power cord or PSU (even the best can be faulty, or fail). And never assume your wall outlet is properly wired or grounded either.
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