my D7 has a solid state rectifier fitted, i have it in my head that it came off a triumph, would i be better fitting an original one? my problem is when the d7 is started and you turn on the lights the engine cuts out and the battery soon goes flat.
If you're referring to a little square alloy block about 1.5 inches square, then you're better off keeping it.
If you're referring to a round black disc type, then the same applies compared to the original d7 type.
Battery going flat is another issue, if you're on 6volts then measure the voltage across the battery with the engine running , should be around 6.5v maybe shade more.
Finally, the best battery for a d7 is a wet , lead acid 9 or 10 Ah.
The headlights run directly of ac from the generator, the engine generator supplies ac to the rectifierr to charge the battery for things like horn, stop and pilot.and possibly ignition depending on how many switches are in the headlamp.