VESC possibly fried

I have two new VESCs from DIY. I set them both up via the BLDC tool. One was fully connected to the motor, battery, and transmitter. It was working fine when tested. Next, I connected the 2nd VESC via the XT90 parallel connector. At that point, both VESCs stopped working. The lights now no longer go on for both VESCs. They don’t connect to the BLDC tool.

My battery is a 8s.

It check the wiring. It doesn’t seem to be reverse polarity since one VESC was working.

Any thoughts on what I should do now? If I buy new ones, I don’t want the same thing to happen. Or maybe there is a simple repair. I would appreciate any advice.

You plugged in 2nd vesc while first was powered on? Some pics would also be helpful, all the wiring, vesc, etc

Ahh seems you likely blew can transciever If connected via can, you must power on at the same time

Yes. 1st was power on. I just added pics.

Can it be repaired?

Quite easily

Thanks for your help!!!

If want to be sure you can always follow these step.

Thanks. I just ordered a multimeter.

If you cant fix them I’d take them off your hands for the price of 1 new one.

Good to know.

I have been searching for more information on repairing the U401. Is there anything else that will get me more info?

U need a smd reflow solder station and then replace this part.

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Thank you.

Get this part?

It looks like I should be getting one of these. https://www.google.com/search?rlz=1C1CHBD_enUS770US770&biw=1536&bih=710&tbm=shop&ei=tesxWriYHoXi_AaE0b6QDA&q=can+bus+transceiver&oq=can+bus+transceiver&gs_l=psy-ab.3...6256.12510.0.12846.38.27.1.0.0.0.417.2344.16j4j1j0j1.22.0....0...1c.1.64.psy-ab..19.7.990...0.0.nMsBMSv2FMs

Anyone know exactly which one?

https://github.com/vedderb/bldc-hardware/blob/master/design/BLDC4.12_BOM.ods