Teensy 3.5 died silently

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campfool

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My first post, thanks in advance for forgiving/correcting any posting violations I may make.
I'll gladly post code if asked but i don't see how that would be of use in this case.

I've been working with Teensy 3.5 & Audio Board the past few days that I had powered/connected by USB to macbook. In addition I have a small strip of 24 WS2812b connected to pin 24 (data) powered by separate regulated 5v supply. This has all worked perfectly well until an hour ago when I needed the USB port for something else. When I replugged the Teensy back into the USB port - nothing. No smoke, no sound, but no life from the Teensy either. I tried plugging it in to another previously know working laptop's USB but still nothing. Checked LEDs, they are fine.


I assume I blew the Teensy but I'm not sure what I did wrong, it had been working fine for several days. Any ideas what I broke & how to prevent it in the future?

Originally I had the LEDs GND connected to the Teensy GND pin located across from pin 24, but the LEDs worked fine without so I disconnected it two days ago. Could that have led to blowing the Teensy?

A sincere thanks for any advice.
 
There are 'troubleshoot' tips for checking voltage at key points and trying simple blink to see if Teensy is blown.
If the power was from external supply but only GND was through Teensy - all that return current passed through the Teensy. I was doing 32x32 matrix and was seeing over 1 AMP passing back to USB from Teensy because the GND to external supply was not the easy path until I added another wire. And that was with Vin<>VUSB line cut. I noticed an issue uploading programs but didn't see any damage before added GND to Supply.
I did a 32 RGB strip off PropShield - using limited LED's - and that did not cause trouble on T_LC or T_3.2 at the time - but that was limited by USB power without external supply path.
 
There are 'troubleshoot' tips for checking voltage at key points and trying simple blink to see if Teensy is blown.
If the power was from external supply but only GND was through Teensy - all that return current passed through the Teensy. I was doing 32x32 matrix and was seeing over 1 AMP passing back to USB from Teensy because the GND to external supply was not the easy path until I added another wire. And that was with Vin<>VUSB line cut. I noticed an issue uploading programs but didn't see any damage before added GND to Supply.
I did a 32 RGB strip off PropShield - using limited LED's - and that did not cause trouble on T_LC or T_3.2 at the time - but that was limited by USB power without external supply path.

Thanks, and I'm fairly certain it was a current surge from the data line. Both the Teensy, through the USB, and the LEDs were both grounded separately at failure time, I should have kept the grounds connected. I'm new to electronics and although I've read to connect grounds it still seems like voodoo to do so. The power supply the LEDs are on is rated for 2amps which I suspect crossed the Teensy momentarily when I plugged the USB back into the computer. Live and learn, tiny Taps for my Teensy, RIP.
 
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