Sturmey archer AG dynohub squeaking

Hello, I have a sturmey archer AG hub running on my bike. I understand how the gear change mechanism works and its all fine down there. However there is an annoying squeak that comes from the general magnet area. I have stripped the hub down twice to try to stop this, I take it apart put it together and then for a while it is fine, then the squeak returns after a week or so. I have looked at the troubleshooting original manuel, I have read all sheldon brown has to offer on this hub but I simply cant solve this one. I had the same problem with the GH6 dynohub and never got to the bottom of that either. I am considering just scrapping it though getting a new wheel would be expensive and it does power my LED lights very well so it would be a shame.

Could anyone please advise me on this one, its a horrid problem that has gone on and on and on and its just driving me nuts!

anyone?