I've tried three separate builds on one particular frame, and each time when powering up for the first time I've blown one of the ESCs. I've used (at least) two PDBs and FCs as part of this (might have repeated across two of the builds); each time it's been stripped all the way down. The only things constant to the builds are the motors and the frame. (Meantime I've done 7 other builds on other frames, none of which have problems.)

What steps do you go through in tracing a short circuit? I obviously don't see anything obvious. The PDB when unconnected to any ESCs is fine. The ESCs are insulated from the frame.

Also I'm a little confused by the shorted ESCs, or perhaps my multimeter. Switching the multimeter to 2k Ohms and running red to black / black to red on the ESC leads, I get about .550 on each ESC (which, if I'm interpreting it right, means there's a circuit through the ESC, i.e. non infinite resistance - right?) Should I expect to see any difference in a smoked ESC vs a non smoked ESC?

Finally, what does anybody use for quickly testing suspect ESCs? I now have a box of 12 suspect ESCs, 9 of which are probably good. I have an ESC tester (YKS servo tester / Turnigy thrust stand) but since I cut off ESC plugs when assembling that's a chunk of soldering time involved in each test. Is there an ESC testing rig with bulldog clips that'd make life easier for me?

The way I check for short is to use DMM on continuity mode. Probe the pos and neg of the lipo pad. If you don't have continuity mode, you can use the Ohm function. If you get a small resistance or value, then there is a short in your circuit.

Thanks. So I shouldn't see any value, i.e. it should remain at infinite?

To be clear, I was getting infinite on the PDB pads. As above I get a low-ish value on ESCs (but only when I do red to black; black to red), even on ESCs that test as working. This seems OK?

Is it possible that the multimeter wouldn't find issues that e.g. only become apparently with a good amount of current flowing through?

(17-Dec-2018, 12:28 AM)beatbox Wrote: So I shouldn't see any value, i.e. it should remain at infinite?

Yes, a continuity or resistance test across the positive and negative LiPo pads should show an open circuit (or "Open Loop" in EE language), however there is an exception to that rule...

If you have a capacitor connected across the power terminals whether it be a noise cancelling electrolytic capacitor that we generally fit to our quads, or a noise filtering circuit somewhere on the board, then with the positive lead of the meter placed on the positive pad and the negative lead of the meter placed on the negative pad, you will see a high resistance (in the KΩ range) that will steadily start to rise as the capacitor is charging up. This will eventually end up in the MΩ range and may even go to infinity (Open Loop) if you leave it long enough.

The same happens if you use the continuity beeper. It will initially start to beep until the resistance gets to a high enough point (as the capacitor charges up) that the beeper shuts off because a multimeter will have an assumed high resistance threshold whereby it deems there to be no longer any continuity even though there may still be a very high resistance value present.