I have a shimano hub dynamo running an Edulux front light but trying to connect in a Smart TL267RG tail light (led). I can run either light but not the two together. It won't work either in series or parallel. Both lights are self earthing ie I use the frame to connect back to the dynamo. What is the way to do this please?

Maybe try skipping the self earthing and run two dedicated wires to each light straight from the hub? With painted frames and road grime it's questionable how well most frames actually are at transmitting electricity anyways.

Hub dynamos are usually alternators by now, so frame ground
like the DC Union bottle dynamos of old is not applicable.

I am not familiar with the Smart tail light, but a hub dynamo puts out an AC voltage, and LEDs require a DC voltage. There needs to be some rectification that takes place. In the case of the Edulux headlight, there is a full wave rectifier built into the light - my guess is that the tail light does not have rectification built in, but relies on the fact that the LED by itself will provide rectification. I use the Supernova E3 headlight, which has a DC output from the internal rectifier to power an LED tail light.

What you might try is to go to Radioshack and buy a "Full-Wave Bridge rectifier" It will have two terminals marked with a ~ and then two marked + and -. Connect the two marked ~ to the dynamo, in parallel with the Edelux headlight, and then connect the other two to your tail light - you may need to swap the polarity of the taillight to get it to work right....

Mark

most tail lights will take the dyno output directly. The E3 taillight is an exception, and I suppose it's possible that the Smart light also requires a special headlight. I couldn't see any instructions online, so it's hard to know for sure

The Edulux has a blade connector to attach the taillight wiring to, according to this:
https://www.nabendynamo.de/produkte/p...e_Edelux_e.pdf

I don't have either light myself...
Good luck.