Focbox: Did I kill both in 1ms? HELP

It’s not diode it’s TVS

there is 5.1v on that GH12E there is no voltage on the big black GFZ 74A diode.

now I check the rest.

there is some small black chip near the can bus connector. it has 6.7v

I didn’t read the entire thread, but if noone has said yet…when using can bus you should start the VESCs up at the same time or you risk killing can bus.


and you do not need to connect 5V

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My CAN bus cable only has the data cables

Yeah, but it is doing a ground loop that can kill both Focbox… remove U401 and use split ppm or replace it.

If you want to be sure just check if c25 is shorted.

I don’t what you’re talking about, but yes it is a TVS


I measured C25 like you described in the other thread. I took the multi-meter and it does “beeeeepp” - is this the meaning of shorted?

C23 on the top side does not beep - it shows 5.1v

yes exactly.

Edit: so basically U401 is Blown


And I am still unsure - what U401 is.

Johonny - thanks for you help!

So I need this U401 and also the TSV? The one that has this white powder on it in my pictures?

No TVS is fine.

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what is the exact name of U401 - so I can search for it.


is it this one?

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Yes it is :slight_smile:(10Char)

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And those two focboxes got killed - because one was powered on and the other 10sec later?

Yeah, you have to power them simultaneously, or you occur the risk of creating a ground loop that will kill both can transceiver

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Understood - I just realized it was the first time that the boxes were NOT powered on simultaneously - because I used two Vedder Anti-Spark switches with two power-buttons.

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