mechatrons
Hackscribble has tested your code, and says the led does not turn off. Others, including me, look at the code and say, yes, the led won't turn off because there is no writing LOW in the repeat task function.
You say that the code works fine.
I am having trouble getting beyond this first contradiction. It's hard to focus on the very unusual issue of internal vs external power supply if we can't get over the first hurdle. If you can run Hacksribble's code as posted and the led goes off and then on again on with a 4 second interval, then, then please document that for the group(maybe with some photo's, or a link to a you tube video) and maybe you will get more help and less attitude.