3.3v and GND connected on a T4.1. What did I do?

[Talkiet]

I have a T4.1 (fresh out of bag but bought a couple of years ago) and I put headers on it, soldered a lead to the D- and D+ pads, plugged it in via the new outboard USB-C port and the micro B, flashed a test sketch. all worked. So I put it in the PCB I made (and that works with other T4.1s) and it wouldn't boot. Some troubleshooting later and I find that the GND and 3.3v lins are bridged somewhere on the T4.1. Could I have killed it in this way somehow? Is this a possible failure mode I could have created?

I removed the pin headers form the gnd and 3.3v by the USB to see if I trapped a bit of solder under them but nope - GND and 3.3v are still bridged.

Not too concerned about losing a T4.1 - but am concerned if I did something to kill it this way - I did nothing different to the last time I aassembled one of these projects.

Cheers - Neil G

 

[defragster]

Nice pics - indeed that seems clean.

Not shown:: Anything Fishy here and here?:
Just beyond 1.4" on the T_4.1 are 3.3V and GND on opposite sides.
Another GND and 3.3V are side by side on the cross pins behind the SD card socket

 

[Talkiet]

I haven't pulled the rest of the pins out yet (I am aware there are other 3.3 and GNDs) - I thought I would check to see if this is a known possible failure first... I don't think I put any power through it wrong - the board does have a couple of dc-dc stepdowns (The project is powered off 12v and steps down to 5v for the Teensy and 10V for a LORA device and thermal printer) and they are back fed if I am running the Teensy from USB to program it but that has never caused an issue in the boards I have assembled so far (10-12 of them).

I guess I'll pull off the other 3.3and GND pins and check but I am not confident that's it. Putting th epins on was really simple and there's a couple of oversoldered joints but I have checked it with a microscope and everything visible is clean.

Cheers - N