VESC 4.12 3.3V Shorted

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Mk32784
Posts: 9
Joined: 08 May 2017, 11:11

VESC 4.12 3.3V Shorted

Postby Mk32784 » 28 May 2017, 09:00

Hello all,

I had two VESC randomly "died".
After doing some debugging the 3.3v rail is shorted out for some reason.

The TC2117 regulator is getting 5.15V from the DVR but it's overheating and going into thermal shut down from the 3.3v being shorted. I removed the TC2117 and the STM32 (i have basic hot air equipment) and the short still exists so it's not either of those components.

Any thoughts? I looked at the schematic and can't seem to find any issues with the board. Checked all the plugs and and don't find anything physically bridged either.

arvidb
Posts: 223
Joined: 26 Dec 2015, 14:38
Location: Sweden, Stockholm

Re: VESC 4.12 3.3V Shorted

Postby arvidb » 28 May 2017, 11:17

C25 (the tantalum cap) maybe?

Mk32784
Posts: 9
Joined: 08 May 2017, 11:11

Re: VESC 4.12 3.3V Shorted

Postby Mk32784 » 28 May 2017, 21:53

arvidb wrote:C25 (the tantalum cap) maybe?


Removed both caps and there's still a short....

I'll take some photos and see if anyone can spot something

Mk32784
Posts: 9
Joined: 08 May 2017, 11:11

Re: VESC 4.12 3.3V Shorted

Postby Mk32784 » 28 May 2017, 22:43

Photos of the board http://imgur.com/a/GxgkS

rew
Posts: 924
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: VESC 4.12 3.3V Shorted

Postby rew » 29 May 2017, 06:31

I can click on a picture to enlarge it to the size of my browser window. But assuming you took high-res pictures there should be more pixels available. When enlarged the cursor remains a "increase -zoom" icon, but clicking again removes the zoomed version.

Mk32784
Posts: 9
Joined: 08 May 2017, 11:11

Re: VESC 4.12 3.3V Shorted

Postby Mk32784 » 29 May 2017, 11:14

rew wrote:I can click on a picture to enlarge it to the size of my browser window. But assuming you took high-res pictures there should be more pixels available. When enlarged the cursor remains a "increase -zoom" icon, but clicking again removes the zoomed version.


Yeah it seems the internet likes to compress everything... here's full resolution. Thanks for taking a look
https://www.dropbox.com/sh/87i2gl46ss53 ... h74na?dl=0

Reading through the documentation it seems that the 3.3v double backs into the DVR at 2 pins. Removed the DVR and the short still exists :cry:

rew
Posts: 924
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: VESC 4.12 3.3V Shorted

Postby rew » 29 May 2017, 20:18

Yeah. That was to be expected: The DRV is not actually powered by the 3.3V, it just uses it as a reference voltage. Not likely to short there....

Mk32784
Posts: 9
Joined: 08 May 2017, 11:11

Re: VESC 4.12 3.3V Shorted

Postby Mk32784 » 30 May 2017, 04:17

rew wrote:Yeah. That was to be expected: The DRV is not actually powered by the 3.3V, it just uses it as a reference voltage. Not likely to short there....


That's what it thought but I am basically out of ideas at this point :(

rew
Posts: 924
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: VESC 4.12 3.3V Shorted

Postby rew » 30 May 2017, 04:36

To find a short...

Apply say 0.5V, current limited to an appropriate value by a lab power supply. Use the correct/normal polarity. Use the design files. You can now measure for each track if there is a voltage drop or not. If there is a voltage drop, that track is carrying current. Use the mV range of your multimeter.

Mk32784
Posts: 9
Joined: 08 May 2017, 11:11

Re: VESC 4.12 3.3V Shorted

Postby Mk32784 » 30 May 2017, 09:09

rew wrote:To find a short...

Apply say 0.5V, current limited to an appropriate value by a lab power supply. Use the correct/normal polarity. Use the design files. You can now measure for each track if there is a voltage drop or not. If there is a voltage drop, that track is carrying current. Use the mV range of your multimeter.


welp i acutally found the issue.

The SN65HVD232 Can bus chip was fired. Shorting 3.3v and Ground.

Removed it and replaced it with one from another board and now everything works!

Thanks for the help.


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