My first two dynohub setups used a SP hub. That hub is not grounded to the fork. So, the third time I put together a lighting system I was stumped for hours trying to figure out why the Shimano hub was not working out. And since I already had set up two bikes with dynohubs, I of course knew it all. I eventually figured out that the Shimano hub was grounded to the fork and so was my headlamp, thus switching the wires fixed it.

And, a couple months ago I changed headlamps on a bike, did not hook up the taillight until I was sure that the headlight was working, and headlight was intermittent. Then finally figured out that the taillight wiring that I had not hooked up yet was occasionally touching the contacts and shorting out all the power. It is amazing how something as simple as these lighting systems can be so troublesome.

I was unaware that Sturmey Archer still made dynohubs, I do not think I have seen one for a couple decades, I learned something from you too.