You wanted to incant @Jon_Jack from engineering.
Just wanted to let everyone know, we are looking into these reports. Once we get a few of these failed motors back we will dig in and let you know what we find.
Iāve seen the same problems. I had two die identically; both were from a new super kit.
I was at a coachesā training this week where the coaches were building the clawbot. One died lifting the arm the first time, mid-stroke. This was from new starter kits that we opened right before assembly.
Yeahā¦ staticās a thing, but too many ppl saying same thing now. Sounds like there was a swap for am incorrectly specād component.
sorry, we didnāt open them up - didnāt want to void the warranty and wanted to get them to VEX support for their review.
Itās worth noting that any warranty terms that void the warranty for simply opening a product or breaking a sticker are actually illegal according to the FTC. To their credit, VEX does not appear to have any such terms in their warranty as well. Disassemble and learn all you want; youāre only voiding your warranty if you damage something while doing so.
Thanks to @district9 I now have a picture of the PCB of the Rev 10 motor:
Lets compare this with Rev 7 motor I had around:
We can see that there are a few changes in the lower left portion of the board, in the area between the motor controller and the MCU, including the addition of a new component which I have not been able to identify yet:
We also spot an interesting and potentially significant change: the Motor controller (upper left and slightly smaller square) is now a TI 8701E whereas previously the Rev 7 motor used a TI 8701P:
The datasheet says that the difference is that the P variant uses 2 PWM inputs for control, whereas the E variant uses a āPhaseā and āEnableā pin set, which effectively mean a direction pin and a duty cycle pin. this would also mean that the firmware on these parts would likely have to be somewhat different in order to utilize this different interface.
Looking on TIās website we see 2 differing truth tables for these parts:
Of note, there is no entry in the truth table for the E variant for Coast mode. This does not necessarily mean any change to the abilities of the brake modes of the V5 motor, but it is potentially relevant. If anyone has a working Rev 10 motor it would be great if they could do a comparison of the coast behavior of that motor vs a Rev 7 motor.
Please take all this with a huge grain of salt; there are many valid reasons to swap out components in an electrical device (supply chain, etc). We should wait until VEX responds with the conclusions of their investigation before jumping to conclusions of our own. I just wanted to take this chance to provide some insight into the literal black box that is the V5 motor for educational purposes.
Is that heatsink paste under the āPā chip?
No, there arenāt any heatsinks on any of the motor components. Probably just some dirt, Iāve had this board out for a couple years now. I cracked open another Rev 7 motor to confirm and yeah, pins are clean like the Rev 10 board.
Ok. Maybe Iām remembering seeing small chips xfer heat to the board itself this way.
Now that V5 motors have begun shipping again, I opened one up to see what changed:
It looks like the new motors now shipping have switched to Rev 8 boards, in contrast to the problematic Rev 10 motors. I canāt seem to find any easily visible differences when compared to Rev 7, and the original Rev 7 motor controller, the TI 8701P, has returned.