Press and hold power button for ten seconds?

[komatsu]

from the iFixit website:
"Before beginning any work on your iMac: Unplug the computer and press and hold the power button for ten seconds to discharge the power supply's capacitors"

Do you do this before opening iMacs?

 

[nambuccaheadsau]

Have on both Mac Pros and iMacs. Then I still use the wrist strap to be sure to be sure.

 

[komatsu]

and do you hold the power button for 10 seconds before opening them up?

 

[wardie]

Didn’t know it did that thanks! I always use a wrist strap onto the grounded case anyway (to be sure)^2

 

[J.Gallardo]

Umm... I think the use of a wrist strap has nothing to do with discharging power supply capacitors!
Those capacitors can discharge on you, and could cause a really big electric shock (and wrist strap won't stop that). When you keep the circuit closed by pressing power button, they get discharged.
I believe wrist strap is used to eliminate small electrostatic charges that could affect delicate electronic components while manipulating them.

 

[wardie]

Umm... I think the use of a wrist strap has nothing to do with discharging power supply capacitors!
Those capacitors can discharge on you, and could cause a really big electric shock (and wrist strap won't stop that). When you keep the circuit closed by pressing power button, they get discharged.
I believe wrist strap is used to eliminate small electrostatic charges that could affect delicate electronic components while manipulating them.

Good point hence my interest. Didn’t realise they held a lot of energy or that you could discharge it.

 

[komatsu]

Umm... I think the use of a wrist strap has nothing to do with discharging power supply capacitors!
Those capacitors can discharge on you, and could cause a really big electric shock (and wrist strap won't stop that). When you keep the circuit closed by pressing power button, they get discharged.
I believe wrist strap is used to eliminate small electrostatic charges that could affect delicate electronic components while manipulating them.

Any ideas why this does not happen with a PC motherboard? (Yes, technically it can happen but I've yet to see it)

 

[Trebuin]

Umm... I think the use of a wrist strap has nothing to do with discharging power supply capacitors!
Those capacitors can discharge on you, and could cause a really big electric shock (and wrist strap won't stop that). When you keep the circuit closed by pressing power button, they get discharged.
I believe wrist strap is used to eliminate small electrostatic charges that could affect delicate electronic components while manipulating them.

Much like that same wrist strap won't stop you from burning your hand when someone touches the hot plate on a coffee brewer that was just turned off a few seconds earlier.
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Any ideas why this does not happen with a PC motherboard? (Yes, technically it can happen but I've yet to see it)

Depends on the design. It's the capacitors that can cause harm to either you or the motherboard. Apple has them integrated with their hardware for imacs and in the external power bricks for older macbooks. PCs have them inside that big power supply in the computer, or in the external power brick.

 

[J.Gallardo]

I’ve openned and done things into an old iMac of mine. I didn’t do what iFixIt recommends... but I’ll do next time.
No big effort to be safer!
I’m used to read this advice about opening various kind of devices... Just be careful with big charge capacitors & try to discharge them. I’m over 50 and remember that it was widely known by old school technicians.

 

[komatsu]

thanks.

I heard the stories...one errant screwdriver on a live logicboard and it's toast!