Is my Teensy 4.0 dead?


New member
Hi everyone, I'm trying to figure out if my (very new) T4.0 is dead/unrescueable.

Yesterday, I received a brand new T4.0 with headers presoldered and an Audio Shield from Digi-Key. I connected them together and ran the example sketch WavFilePlayer to confirm that they worked (they did), but after unplugging and plugging it in to my computer, my computer would not recognize the Teensy, nor would the audio play or the red LED blink. The last time the Teensy was functioning, I was powering it via USB with an iHome portable power bank which allegedly supplies 5V/2.1A. A Bluetooth speaker was plugged into the Audio Shield's headphone out, and the speaker made a popping noise when the Teensy was disconnected from power.

Plugging the Teensy alone into my computer, the Vin pin yields 5.1V, but the pins for 3.3V and Program are at ~0.01V. The ARM chip gets warm to the usual amount. Holding the Program button while plugging in the Teensy does nothing.

Is there anything I can do to reset the Teensy and have it function again? If not, can anyone educate me on what I did wrong so I don't have this happen again? :(

Additional Info:

Powering the Teensy from the same power bank (which was been discharged further since last night), Vin yields 4.94V.
Following instructions from this thread, the resistance between 3.3V and Ground is ~190K when the Teensy is unpowered.
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Well... I bought a new T4.0 and foolishly plugged it into the same power bank again. It's now dead.

I don't even know what to take away from this experience. Are Teensies just more fragile than I thought? I for sure will NOT be using this power bank to power a microcontroller ever again, although I've never had problems with it charging my phone.
Thanks for the tip. I also could not find it on the web, it's probably at least 3 years old.


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Forum won't let me upload a photo.

Here's the info taken directly from this forum's "Manage Attachments" page (apologies for the poor formatting induced during conversion from original tab-delimited to spaced !!):

Filetype               Max File-size     Max Width        Max Height
 bmp                   390.6 KB          1280             1024
 c                     488.3 KB          -                -
 cpp                   488.3 KB          -                -
 doc                   488.3 KB          -                -
 gif                   244.1 KB          1280             1024
 h                     244.1 KB          -                -
 ino                   244.1 KB          -                -
 jpe                   390.6 KB          1280             1024
 jpeg                  390.6 KB          1280             1024
 jpg                   390.6 KB          1280             1024
 pde                   244.1 KB          -                -
 pdf                    1.43 MB          -                -
 png                   781.3 KB          1280             1024
 psd                   390.6 KB          1280             1024
 txt                   195.3 KB          -                -
 xls                   390.6 KB          -                -
 zip                    1.91 MB          -                -

Mark J Culross
This "20220718_093527.jpg" uploaded - it is 4000 x 1868 pixels and 1.52 MB on disk and it uploaded.
When uploaded the hover says it is 69.5 KB so it mangles the image for storage.

20220718_093527.jpg <replaced with edited image that was now 1.28 MB
It is a NOTE 3 AT&T took in trade for $800 credit toward a new phone - the store staff said they need old phones for parts to help with the parts shortage.
Battery bloated and popped out the old home button and cracked the screen. But it still powers on.

And clicking the image gets this in the HTML:
width: 901px;
aspect-ratio: auto 901 / 421;
height: 421px;
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In case anyone's wondering, the powerbank is a 6000 mAh iHome IH-PP2042. Forum won't let me upload a photo.

That is odd - I've used a few such packs and not had trouble - never that brand. Wonder what the output voltage is?
It looks like normal packaging in good shape too.
This "20220718_093527.jpg" uploaded - it is 4000 x 1868 pixels and 1.52 MB on disk and it uploaded.
When uploaded the hover says it is 69.5 KB so it mangles the image for storage.

When I do a "Save image as" by right-clicking on the picture in the post, according to Windows Properties, the resulting file is 69.6K, with dimensions 1280 x 598. Agree that there seems to be all kinds of mangling in the process of creating a picture attachment !! Maybe those limits reported by the forum's "Manage Attachments" page are "post-mangling", which really isn't much help at all when trying to attach a picture !! Even though that's the only information available/provided when trying to attach a picture, I doubt that updating that "Manage Attachments" page would make it very high on the priority list, if even at all !!

Mark J Culross