[luke_nicholls]

I've just finished my first soldering job for my new quads ESCS and PDB, finished it, and tested it by plugging in a battery. all the ESCS did their beeps and they where all fine. I went onto libre pilot to first calibrate them, and then when i got to the minimal outputs part (where you add just enough throttle so the motor spins slowly) every motor on the quad did not spin properly and was only going backwards and forwards rapidly. I've tried changed 2 of the wires around on the ESCS but got the same result. Any help on this would be appreciated. thanks 

[TheOtherCliff]

That sounds bad.  That is what it does when only 2 of the 3 motors wires are connected.  And that usually means that either the motor is burned up or the ESC is burned up.  It could mean that those ESCs don't like those motors though.  That is known to cause "difficult starting"

Make sure that all 3 motor wires are well connected.  With motors disconnected from the ESC, you can measure all possible pairs of the motor wires (1x Ohms scale) and they should act like they are straight shorted wires with 0 ohms.

You might try flipping a prop in the correct direction with it jumping, to see it that makes it start.

After checking the wiring, I would flash the latest firmware (BLHeli or SimonK) to see if that fixes it.

Don't push the throttle high to try to make it start as that can make a "difficult starting" change into "burned out".

Have you seen or smelled smoke at any time?

[luke_nicholls]

i checked the ESC specs that i bought and it turns out they where for 400-450 sized quads (mine is a 210 with 1806 motors) taken them off and will replace them with the correct ESCS.

[TheOtherCliff]

ESCs that are a little too large should work fine.

Did you measure the resistance (Ohms) from each leg of a motor to the others?  You can also do it with a simple battery / light bulb tester where the light bulb lights up if you short the test leads together.

We can do a little more trouble-shooting to avoid spending money that doesn't need to be spent (and waiting for no reason).

[luke_nicholls]

don't have a ammeter or voltmeter so couldn't do so, don't have a bulb laying around anywhere either, is there any other way i could test it. i do however have a little voltmeter thats intended to go on your balance lead if that would work?

[TheOtherCliff]

Cheap ohm meter (ohms X1 is important, not like 10K=10000) would be best, but the key is that each motor lead to each other motor lead should act like a straight wire connection and easily pass several amps of current.

<-----wire-----bulb-----battery-----wire----->

You short the two wires together and the bulb lights.  Touching the two test wires to every possible pair of the three motor wires and the bulb should light up each time.

Another way to test requires a current limit in your quad to keep from potentially burning ESC / motor.  A simple automotive bulb such as #1156 works fine for a current limit (and for the previous simple tester).  Test just one motor.  Undo one motor lead and retest.  Did startup change (probably much worse)?  It should change.  Try all three, disconnecting a single motor wire at a time and leaving the other two motor wires connected.  If you find one where it doesn't change, then that lead is probably already "open".  It still could be ESC or motor though.

[luke_nicholls]

UPDATE - fixed this by replacing the secs and its fine now.

[TheOtherCliff]

The ESCs may still be usable if you upgrade the firmware in them.  I had a set of ESCs that were hard to start but now work fine since I flashed the latest firmware.  They were really cheap eBay ESCs.  It seems the only thing wrong was an old firmware version.

Flashing ESC firmware is a good thing to learn if you consider this a life long hobby.  Research BLHeli and SimonK.