How to diagnose a short circuit?

[jgentes]

We have many RevPi Core 3 devices in the field, and one of our customers reported that they 'definitely traced the 24v short to the RevPi card'.

We are very motivated to diagnose the cause of this problem and find a solution. The device was most likely not grounded - could that cause this?

What else can we do to discover the root cause?

We are having the device shipped back to us, which we could then ship to you if needed. We need to know if this is a potential issue with all of our installed devices.

Thanks,

-James

[dirk]

Dear James,
can you please provide more information about the hardware setup and the connected peripherals?
I.e. what USB devices, HDMI, I/O modules are connected to the RevPi?
How did the customer measure the short cirquit?
Is the device not working any more or does it boot?
Are there suspicious entries and in the log files i.e. kern.log?
How about the environment where the devices have been used? I.e. is it a hot environment, etc.

[jgentes]

Hi Dirk,

Here's what I know so far:

- We had a USB wifi dongle in the system, that's the only peripheral. No other connections other than the power.
- They mentioned "When you plug the device in it will shut the machine down by taking out the power supply."
- We are having the device sent to us so we can inspect the logs
- The environment is a factory, likely inside of a controller on a production line. It's probably hot, but I wouldn't expect it is outside of the tested temperature range of the RevPi.

We will try to get more info, any other diagnostic info you can provide would be helpeful.

[dirk]

Dear James, after a review with our hardware specialists I can say the following: If there has been an enormous overvoltage then the TVS diod on the input may react in a permanent short cirquit. Another idea is that the power supply could be the root cause. Anyhow I can say that we have to examine the device with some hardware specialists. I'll send you a RMA.

[broofa]

Hi Dirk,

I work with James (above). We've received the faulty device from our customer. I opened the device and noticed very obvious signs of a short on the main board, as well as soot on the inside of the case. Photos attached, as well as a photo we received from the customer showing the device installed in their work cell here: https://imgur.com/a/hqQEK0s.

I don't have any further info about the nature of the installation (such as power supply type or other devices connected to the supply) unfortunately.

I connected a multimeter across the power inputs and verified it is indeed shorted (0 Ohms, both directions). I [briefly] tried to power the device on and it exhibited the behavior our customer described - shorting out the power supply and taking down the other device (another revpi core) we had connected to the same supply. (FWIW, here's the supply I tested with: https://www.trcelectronics.com/View/Mea ... 0-24.shtml) ... so we don't currently have a way to pull any data off the device.

If you could get us an RMA, I'd be happy to send this to you for further inspection.

[dirk]

Dear broofa, I am sorry to hear from the troubles. Thank you for all the pictures you provided. I'll send you an RMA form via E-Mail.