Magsafe adapter - Any electricians around?

[fwwwn]

So I got my new MBP over the weekend - very stoked - but I seem to have a problem with the grounding of the adapter.

By now, most MBP or aluminium mac users should know that if the computer isn't grounded you get a slight tingling sensation when you touch the case. However, when you hook it up to a three prong plug, it usually fixes this by grounding the case.

I got a three prong cable with the MBP, which worked fine (it was grounded), but it was slightly frayed due to a moulding issue on the cable itself, so I returned it to the store for a new cable which was 2 prong. I cut the plug off and attached my own 3 prong plug (as I did with my iMac) but it still seems ungrounded - at home and at the office. Where could it have gone wrong? I'm pretty sure it was wired correctly as it works fine in terms of charging the computer. I'll double check the plug again at home tonight, but what else could it be?



BTW the fact that the case isn't grounded isn't a safety issue. Apparently people have measured the potential at 110v (220v but the phase or something is 110v - haven't studied this stuff in 5 years) but the amps are so low it does nothing. Or so Apple says - many of the Magsafe adapter plugs are only 2 prong anyway.

 

[creeper]

I've had the MBP for a year and recall the old ones did give the tingle, but the new ones don't. What I have noticed is if the electricity supply is unstable where you plug in the power supply, it tends to still do the "tingle" thing. But otherwise, you shouldn't have the problem.

 

[OomD]

...I cut the plug off and attached my own 3 prong plug (as I did with my iMac) but it still seems ungrounded...

Well if it had the 2-prong plug then it only had 2 wires inside... So even if you fit the 3-prong plug it wouldn't help unless you actually connected a wire to the third (earth) prong. Did you do that? Or is the earth prong left with no wire connected to it (inside the plug)?

 

[FrancTheTank]

Have you tried swapping the live and neutral wires? - within your added 3-prong plug.

In theory this should make a difference, but more often than not (on basic power supplies it does not.) Perhaps because its a switching supply it may make a difference.

 

[fwwwn]

Well if it had the 2-prong plug then it only had 2 wires inside... So even if you fit the 3-prong plug it wouldn't help unless you actually connected a wire to the third (earth) prong. Did you do that? Or is the earth prong left with no wire connected to it (inside the plug)?

By two prong I meant the specific two prong plug that we get with Apple products (think it's french or euro) - it fits in our two prong sockets, but it actually has it's own socket for the earth, which would be a prong sticking out of the wall socket. When you cut the cable off, it has the standard three colour coded wires inside, which are all hooked up to the prongs in the plug.

 

[fwwwn]

Have you tried swapping the live and neutral wires? - within your added 3-prong plug.

In theory this should make a difference, but more often than not (on basic power supplies it does not.) Perhaps because its a switching supply it may make a difference.

Hmmm interesting. In theory, I should be able to do this, as the standard two (actually 3, but two in SA as explained above) can be fitted either way around. It won't make anything blow up though, right? :/

Also, I'm quite interested as to how this is possible... How does the power supply work with the live connected to either wire? Please inform this retard (when it comes to electricity)

 

[OomD]

How does the power supply work with the live connected to either wire? Please inform this retard (when it comes to electricity)

The polarity swops around 50 times a second (hence 50HZ AC.... Alternating Current) this the live are just conceptual. For single-phase at least. Another ballgame with 3-phase, but not to worry all houses are single-phase. So for your connections it doesn't really matter.

 

[fwwwn]

The polarity swops around 50 times a second (hence 50HZ AC.... Alternating Current) this the live are just conceptual. For single-phase at least. Another ballgame with 3-phase, but not to worry all houses are single-phase. So for your connections it doesn't really matter.

Fair enough, I can understand that. Brain fart when it came to AC. So "Live" and "Neutral" actually don't mean anything for AC single-phase? Kinda seems pointless to colour code each wire then? Why not just have 2 black wires and one Earth wire?

So it will be completely safe to reverse the blue and brown wires in my understanding. Will try this out tonight. Also, will this actually make a difference? In theory?

Update:
So I got home, cut off 3 cm of cord, rewired the plug and it seems to have fixed it. It's such a subtle feeling that it is hard to tell. Will probably only be sure tomorrow.