I was getting frustrated today. I had convinced myself that my VRM install had gone wrong somehow.
Mr Cohrs suggested that I try this test procedure. A 9 volt battery. Alligator clip jumper from the battery negative to a ground lug, and get your negative multimeter probe stuck in this same alligator clip. Then put another jumper from battery positive to the B+ in on the VRM.
Put your positive multimeter probe on the VRM's B+ out tab.
Twist the dial on your VRM.
I got about 5.9 volts with the VRM twisted up to max, and down to zero turning the VRM the other way.
One caution: it doesn't start responding normally right away. I think something in the mosfet must need to build up a charge because initially, there's no response at all. Then for a while the voltage change is delayed - you turn up the VRM, and the voltage readout on your multimeter just
ssllooowwwllyy starts to increase. After a few times through, it responds immediately.
Thanks Mr Cohrs for this cool test procedure.
I had driven myself crazy imagining there was a problem, then I couldn't figure out my imaginary problem
This quick test demonstrated that the problem was just in my head, not in the VRM.