Defective v3.9, CPU instantly hot to touch

I received a DIY install kit from Saber Bay that included a v3.9. I’ve already reached out to them and they should be sending me a new one. I still wanted to see what’s wrong with this one and potentially fix it.

I plugged it in before doing anything else with it and the CPU instantly got hot to the touch. I didn’t get a chance to check if it was recognized by my computer for fear of it bursting into flames or damaging anything else. The cable used works with my other boards just fine. It looks fine upon a quick visual inspection. No obvious signs of damage. Thanks for any help.

I’m grasping at straws here, but it looks as though the two pads circled in red have been soldered at some point. Is it possible there’s a stray strand, blob of solder or even flux residue there that might be contributing to the problem?

Other than that, I can only assume that with nothing else connected, it can, as you say, only be a bad board. Maybe caused by a short beneath a chip somewhere or something like that.

It’s usually pretty hard to track down problems like this.
The solder on the two pads you circled should not be a problem though.
A short under the main CPU is much more likely. BGA components have a small gap between the component and the board, and if anything conductive gets in there it can cause problems.

Sometimes it’s just bad components.

They’re having me send it back anyway. I assumed as much but they hadn’t asked me for it yet.

What are those 2 pads, out of curiosity? I didn’t see them labeled in the docs. Also weird that anything was soldered to the board since it was supposed to be brand new. I didn’t notice at first.

Pads for a 47uF 0805 SMD capacitor. Recommended/Required for BLE modules.

I was unaware of that. I recently installed a 909 on another v3 I had and have had no issues. Should I go back and install it?

On power up, BLE modules, the 909 especially, draw a quick spike of power. In many cases, this results in the CPU not getting enough power and what happens is called a “brown out,” which typically results in the proffieboard crashing on startup.

If it’s working fine, then there’s no reason to install one, but it’s often necessary, so it’s highly recommended.