Cube PWM outputs dying?

I am now looking at what appears to be the second pixhawk cube on Copter 4.0+ that appears to have motor outputs dying. In the field, after pressing the hardware safety switch I get 3-5 ESCs on my hex to properly obtain a signal while the other ESCs remain beeping.

This is after the copter flew perfectly just last week. Not a single issue. I did not change any parameters or hardware, simply packed the copter up, let it sit for a week then took it back out.

So, taking the pixhawk out and putting on the bench with a receiver test shows that 3 of the PWM outputs aren’t putting out anything while each of the others matches the 1000us duty cycle displayed in mission planner. Mission planner shows all 6 motor outputs as having the same 1000us output.

These are T Motor Flame 60A ESCs with only the signal and ground wire running to each ESC.

Have any of you experienced a PWM failure like this before?

It there any reason why not to assign the motor outputs that normally go to motor outputs 1, 2 and 5 to motor outputs 7, 8 and aux 1 respectively? I figure people would have to use aux 1 for a motor output when they’re flight a 12-motor copter etc.

Just trying to find a work around for the time being.

Yes you sure can.
Is there anything else plugged into the motor or aux outputs?

If those Flame ESCs are true opto they will need +5v on that centre/red servo wire.
Use some other external reliable BEC to put 5v on the motor output common supply pins.

Have you tried re seating the cube on the carrier ? I would totally remove it and refit to the board.

Also what carrier are you using ?

But I wouldn’t need to do that if the red pin of the servo cables from the ESCs isn’t connected, right? Each ESC only has signal and ground connected

No I haven’t even thought of this!

I’m using the standard carrier bored. Not the mini and not the core.

I’ll try out reseating the board. Thanks!

As an update to whoever ends up reading this, reseating the cube in the carrier board did not resolve the issue. It remained the same set of PWM outs that no longer worked.

Have you tried flashing to Totally difference model then back so to rover for instance then back.

Yes I have tried that. I am pretty convinced the trouble comes from the electronics on the pixhawk getting burned out specifically when I hotplug the ESCs.

I often power on the copter and let it get lock and connect to the GCS while still screwing the arms on. I am pretty sure thats my mistake.

What ESCs were these ?

T Motor Flame 60A ESCs

Sad to say but I think you’ve answered you’re own question - I wouldnt be hot-plugging anything unless it’s specifically designed for it.
I guess those Cubes could go to use on Quad frames or a test frames that are not critical.

Yea this is far from ideal and not surprising with out some very special precautions in place and then of not recommend it.

First of all why where you doing it that way ?

I have seen people wanting to hear the cube on rote or before take off but you should power down before connecting.

In theory opto ESCs should offer some protection here however again I would also want additional precautions like the connector having different pin lengths allow the Pwm to connect first then ground then positive.

But really this should be avoided overall.