Total Loss of electrical power while riding

[Ethan65]

I have a 1965 Dream 305 and I lost all electrical power suddenly on my ride this past sunday.
The 15a fuse on the hot side of the battery blew
I have 12v at the battery terminals, at the grounds, and at the ignition switch, but no lights, no ignition power.
Im led to believe I have a problem with my regulator/rectifier, which appears to be the original Selenium type.
My question is: how do i test the R/R? I think its a 2 phase

[Ethan65]

Heres some pictures to help

[Tim Allman]

It's possible that your rectifier is the problem but I think it unlikely. Rather than failing by forming a short circuit to ground they tend to fail slowly by increasing their resistance.

On these old bikes it's possible (likely?) that there is a short to ground in the wiring harness. Usually these points of failure can be seen, especially in the handlebar and the wiring in the headlight case.

Keep in mind that fuses sometimes just fail on their own. Buy a box of them and try another.

A multimeter is very useful for tracking down things like this and is not expensive.

Good luck hunting.