How much vibration do you feel

[Davidkoh]

well then i guess my sockets are grounded bec i've never felt that before...

Probobly, might differ from the sockets in different country. Read forums from Sweden where I am from, alot of people have noted this "problem" without grounded sockets.

 

[Boston Fan]

Probobly, might differ from the sockets in different country. Read forums from Sweden where I am from, alot of people have noted this "problem" without grounded sockets.

That's a point I had not considered. The user info on this site does not list locations, so I am never sure where someone is posting from. I am in the U.S., and have not had any problems. Different currents might yield different results.

 

[Sami Koivu]

Test it, I can reproduce that "tingling" sensation when you touch it even when my computer is turned off. If it is plugged into a socked that isn't grounded. Running on battery it never does this, but when you plug it in you feel it. I can even hold my computer and touch other people and they will feel my finger transporting the current.

All Alu MB/ MBP I tested have this, even my brothers old MBP can reproduce this.

I actually have the same (apparently) phenomenon on my Yamaha keyboard. I was trying to understand if it's a potentially dangerous flaw or not and found this document studying the effect as a display method.

http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2582732

The interesting bits:

Electrovibration is tactile sensation of an alternating potential between the human body and a smooth conducing surface when the skin slides over the surface and where the current is too small to stimulate sensory nerves directly. It has been proposed as a high-density tactile display method, for example to display pictographic information to persons who are blind.

...

A common experience for users of ungrounded, line-powered electric appliances (especially older ones) is the sensation of vibration or texture when the skin gently slides over a smooth, metallic part that has an alternating potential. The threshold of sensation, which is sensitive to area, skin locus and condition, subject sensitivity, and frequency, has been reported as low as 2 V 0–P1 [1] for 50-Hz excitation on the back of the knuckle. The fingertips, having thicker skin and often greater hydration, require approximately one order of magnitude greater potential.

 

[james-thescalie]

after reading the 1st post i felt around for ages and couldnt feel anything atall. Your screws around the hdd lose like someone mentioned before? only problem ive had with it is that its booted up slow the past few times but i just sleep it now