After several flights with my new hexa, I've run into a problem. Motor number 3 does not spin when the others do. Long story short, I narrowed it down to something with the PDB. If I plug motor 3 directly into the APM it works fine, but if it's attached via the PDB I get the 3 startup beeps (3S identified), but not the secondary beep that the other motors successfully have.
I completely detached the PDB and did some prodding with my multimeter. When I check the voltage from the ground to the signal pins with ONLY a 3S battery attached to the board, I get various results. Most of them are from 5 to 7 volts, while the signal pin for motor 3 is 12.4 volts (i.e. full battery voltage).
Now, I'm no electrician. Nor am I terribly knowledgeable concerning what these pins should read for voltages, but I'm confident something is amiss.
Is the problem with a 3DR hex PDB?
Yes, that's the one.
For now I have all the motors hooked directly to the APM and it flies, so problem temporarily swept under the rug until I figure out what's going on. I didn't see any obvious damage to the PDB when I inspected it, and all the wires appeared to be intact and exhibit adequate continuity. I'll attack it again one of these days, but for now I'm disappointingly stumped.
Did you assemble the PDB? It is a possibility that one of the header pins suffered a cold solder joint and has broken. Solution re-solder the pins.
Nope, this was RTF from uDrones. I'll check the joints for sure, that's a good idea. But how would that cause high voltage on the pin? I would have assumed a lower voltage from a broken joint. I'll check it out either way, thanks!