Topic: Help Needed / Charging Issue 77 CB750K

[mrmach5]

Working on a friends 77 CB750K , that recently stopped charging. The bike had a new style Reg / Rect installed a couple years ago .
So I started with some tests. First a continuity test on the field coil and tested at spec 7.2 ohms . Then the stator, each segment tested .6-.7ohms outside spec which is .2 . I had new Reg / Rect  handy so installed it just to see any difference, and none. Today I disconnected the white and green wire at the Reg / Rect and used two jumper wires to the battery to power the field coil . Started the bike and it now is making positive voltage. 12 at idle, up to 14.5 at 3500 RPM. Disconnected the Jumpers and tested for voltage at the black , white and green wires. with the key on , black 11.9 volts, white negligible volts. So appears that for some reason the field coil is not receiving battery voltage.
Looking at the wiring diagram, the white comes from the regulator and goes to the alternator. The black comes from the ignition switch with several jump off points.
So at this point I guess you can see I'm out of ideas and any constructive guidance would be much appreciated .

[scottly]

The black wire feeds 12V into the reg, and the white wire is the output from the reg to the field coil. With all wires connected, there should be 12V on the white wire with the key on. If not, the reg is bad.

[69cb750]

The regulator turns the field coil on when needed, your regulator has failed.

[mrmach5]

Yes all testing points back to the Reg / Rect.  The red and white wire has Battery voltage as well as the black wire, but not the white so unable to power the field coil.
So now comes the big question,,,,, the prices on these Regulator / Rectifiers are all over the map , so how do you choose? They start under $20 bucks then on up to $69 bucks , then Rick's at $108 bucks and finally Oregon Electric $159.  Certainly can eliminate the $20 buck choice but what's a good choice for the money??
Thanks

[mrmach5]

Any opinions or experiences with the Regulator /Rectifiers available out there?