rectifier

Twice over the past week, I've experienced a loss of power after riding for about 20 minutes. Then, I notice I've blown the main 15a fuse. Any ideas? My hunch is an issue with the regulator/rectifier which leads to blowing the fuse, then the battery loses charge over time, ultimately impacting...

Ok..my '75 has charging issues, battery won't stay charged,headlight dim, blinkers won't blink etc.... So I pull the voltage regulator off my '72 and try it but no improvement...then I go to pull off the rectifier and notice they are different. The rectifier on '75 seems to be stock like it...