Power adapter issues (#4): Make sure prongs are aligned properly

We continue to report on cases where power adapters for PowerBooks and iBooks fail -- either from user-induced strain on the sensitive area where the power cord attaches to the brick plug-in brick or inexplicable causes.

As previously noted, in some cases, users report a slight crackling or "sizzling" noise when attaching their adapter to the outlet, accompanied by a lack of charge activity.

The most common workaround -- as we've been stating for the past few days -- is to use the extension cord included with the power adapter rather than the two-prong "duck" attachment.

However, we now have some new information regarding why the extension cord works where the "duck" attachment does not -- and it may have more to do with the way the prongs are aligned in the outlet than the presence of the grounding prong on the extension cord.

The bottom line is that if you are experiencing power adapter sizzling, arcing or charging problems with the "duck" attachment, you should try turning it upside down in the outlet to switch the orientation of the prongs.

As described by MacFixIt reader Harvey Chao:

"The use of the grounded cord ensures that the neutral and hot leads for the wall source are properly connected internally to the power supply since with the two prong adapter (which does not have polarized prongs) it can be plugged into the wall source so that either prong is connected to the hot lead. If the wrong prong is "hot" it is possible (without seeing the internal wiring of the adapter) that the "hot" side then becomes the "ground/negative" side of the low voltage appearing at the laptop. This could cause "hot" side leakage to the laptop and hence the reported shocks and tingling sensations.

"A lot depends on the internal design of the power supply - it clearly is a 'switching' power supply design and does not have an isolating 'step down' transformer because it is too small and too light to have such a transformer and yet provide the power output that it is rated to provide. Lack of an isolating power transformer means that hot and neutral leads carried into the internal circuitry must be carefully isolated from the output terminals, but total isolation (without a transformer) is probably not economically possible (relative to the cost of a transformer).

"One suggestion for those using the prong attachment and feeling the shocks would be to unplug the adapter from the wall and then replug it in such that the prongs are reversed - i.e. so that the prong formerly going into the right hand side of the wall outlet now goes into the left hand side. That will reverse the "hot/neutral" input connections and 'may' reduce or eliminate the problem. Of course, if it was correct to begin with, it could also make it worse if it was 'correct' to begin with."

Feedback? Late-breakers@macfixit.com.

Previous coverage:

• Power adapter issues (#3): Reason why the extension cord works when the two-prong adapter does not
• Power adapter issues (#2): Using the extension cord to solve issues; eliminating sizzling noises; more
• Power adapter failure

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