OK. It sounds as if you know about the earth pin and which pin it is. There are a couple of options but I will list the two that are cheapest and easiest and will solve your problem. The manufacturer has included an earth pin. Why would they do this? Usually it is a requirement for safety. In the event of a fault, the earth pin will short the equipment out and blow a fuse or trip the breaker which may save your life. You might then wonder why some equipment doesn’t have this earth pin. In this case the equipment is regarded as double insulated. It should not have any exposed metal parts. Your power supply, does it have labeled on it anywhere:
The words “Class two” or a small picture of a square inside a square
It probably doesn’t, but let us know.
I will put my disclaimer in here to cover myself and say that you should never alter electrical equipment unless you are fully aware of what you are doing, why you are doing it and what the potential risks are. Anything that you do is your responsibility. I am going to list a procedure that will hopefully fix your problem. I am not directing you to do it and if you choose to do it you acknowledge that you understand what you are doing and are taking full responsibility.
Before doing anything. Your power supply – Is it all plastic? It should be. If not stop now. If it is a normal plastic case, and you cannot see any exposed metal read on.
Your first option is to purchase a travel adaptor. I don’t know what these things sell for, but I would imagine a couple of dollars at a cheapie shop. What these will normally do is loose the earth pin. You have to make sure that it has an Australian plug in and out and the earth pin is not passed through. This may not be easy to find.
Your best option and my preferred choice would be to grab a hacksaw or chunky pair of wire cutters and cut the earth pin off. Take a file and file it down level with the plug. Make sure that you cut only the earth pin (make sure you know exactly which pin is earth), don’t damage the other pins and don’t damage the mains cable.
This gets rid of the earth, costs nothing and will hopefully solve your problem. Let me know if you are after any more info or want anything clarified. I don’t recommend this for anything other than a fully plastic power supply used for laptops.
I have heard of this before and heard stories about people who have problems with their laptops, purchase a new laptop only to have the same problem.
Actually I just did a bit of searching around Google and found this:
Why am I getting power supply interference?
Same problem as you have described and looks like they use the same fix. There is a bit of crap in there, so dont take everything they say as fact.
Let me know how it goes.