Teensy 4.0 C29 and L3 components?


New member

Due to a series of unfortunate events I accidentally ripped off the components C29 and L3 on my Teensy 4 board. I’m not skilled enough and/or don’t have the tools to reattach them so I’m assuming the board is cooked and I’ll need to get a new Teensy 4 board but I was curious to know what these components are. I was looking over the technical information but I’m very new to this so I was unable to decipher the documentation.

See attached photo


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C29 is a 10uF decoupling capacitor that could be omitted for getting the Teensy to work again.
L3 is a filtering coil. You could "replace" that part by shorting the 2 corresponding PCB pads.

Thanks for the information! When you say shorting does that mean bridging the left and right pads by connecting the two ends with a wire for example? See photo

Would there be any side effects/impacts on performance of the Teensy


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Yes, just solder a wire where L3 was located.

The side effect could be additional noise coupled to the 3.3V power line. L3 serves to isolate noise from the high frequency switching of the step-down converter from 3.3V to 1.2V (CPU core voltage). If you use the 3.3V pins to power analog circuits, but you don't have any extra noise filtering, they could hear some of that noise. If you have a long wire connected to the 3.3V pin, it could act as an antenna and emit some of that noise as radio waves.

C29 should be replaced. But there's a chance your Teensy might work without it (but have less ability to overclock), since there are still a few other smaller capacitors. But without L3, and with less capacitance, the noise from the switching power coupling to the main 3.3V power will be even worse.
For those 2 broken off parts, you can identify which is L3 and which is C29 using a multimeter in ohms mode.

L3 will measure close to zero ohms.

C29 will initially measure some random amount and will gradually increase as you continue holding the leads in contact. If you briefly remove the leads, it should remain at approximate the prior amount and continue increasing again when you touch them again. You can "reset" it back to a low measurement by touching a piece of metal (wire, paperclip, tweezers) to both sides of the capacitor.