Is there a way to measure the output of the ESCs with a digital VOM or would I need a scope?
When you say “output” what do you mean? If you want to see the voltage being applied to each phase then yes, you’ll need an oscilloscope or something similar.
Thanks Walt, I think that is what I am looking for. I have motors that don’t turn at the same speed. I reloaded the software for the ESC and have checked for physical obstructions or drag. I wanted to check and conform that the power output of the ESCs was the same and make sure I did not have a high resistance break in the wire. Other than swapping control boards, what else can I check?
Interesting problem. There aren’t that many things that will cause the speed of the motor to be different, and you’ve covered some of them. The first thing to check is whether there is anything dragging on the motor (corroded bearings for instance) and it sounds like you’ve checked that already.
You can also get a clue as to whether one motor is dragging by looking at the current that each motor takes. It’s been a long time since I’ve driven a 2.8, so I don’t remember how to bring up the telemetry pane that shows the currents that each motor is taking. But if you can do so, run your ROV forwards and compare the current that each of the horizontal motors is taking. If the slow motor is also drawing more current, then it probably has something holding it up.
If the motor is spinning smoothly, then I doubt its a break in the wire- normally if one of the phases is broken the motor will spin jerkily if it spins at all.
You could measure the DC voltage going into each ESC ( measure between the red and black wires on the side of the ESC that has two wires soldered to the PCB). All of the ESCs should be pretty much identical.
Swapping controller boards, as you mention at the end of your post, is probably the most direct and best method for debugging here, as it neatly cleaves the problem into two- is there a problem with the controller board, or is it a problem with the motors and the wiring? If you have a second 2.8 I would recommend doing that first.
I will let you know what I find.