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Thread: One of six Teensy 4.0s failed

  1. #1
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    One of six Teensy 4.0s failed

    Over the years I've counted over 24 great PJRC products which have never let me down.
    Thanks very much for quality products and informative forums, too!

    I am building a synth (32 waveform + 32 wavetable, 8 channel audio) project utilizing four T4s and a T3.6 (USB MIDI and serial connection to a Processing 3 app) in control of the T4s via serial MIDI. I am anxious to get a few more capabilities operational before demonstrating and sharing.

    On Nov. 30 the last T4 was purchased at the Sharonville, OH Microcenter and I checked to be sure it worked and then placed it back in its ESD envelope.

    Around Dec. 17th, I was attempting to write unique EEPROM board numbers on all six T4s (so that the synth software can react in a distinct way to midi messages). When first powering up the subject T4, I discovered that it died.

    Reviewing a number of online T4 failure reports as a guide, I tried to ensure the problem couldn't be fixed.

    No connections were made to the subject T4. Today, while USB connected, the 5 volt pin was within spec, but the USB current read zero. No LED lights up. The 3V pin read 0 volts. Tried the reset button. Then even tried grounding the program pin for >15 seconds.

    So I am guessing this T4 now has a bad 3.3V regulator.
    I am thinking that there is nothing more to try. Any more suggestions would be appreciated.
    (OK, this is my first time here. Did not see instructions. Don't why there are 2 submit buttons...Please forgive my ignorance of what mistakes i may make...)

  2. #2
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    Schematic shows a 500ma fuse. Has that blown. Should have pads accessible.

  3. #3
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    Thanks very much, Gibbedy, for the info. I glanced at the schematic and saw that. I'll look closer at the board with a magnifying glass and see if i can probe it.
    (Maybe i need a microscope!) It's a little difficult at 76 to probe such small pins and read the meter at the same time. Guess I could ask my wife to read the meter... Happy new year ! ?? Guess I hit [Post Quick Reply] ??

  4. #4
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    Quote Originally Posted by Gibbedy View Post
    Schematic shows a 500ma fuse. Has that blown. Should have pads accessible.
    AFAIK, this is nor really a fuse but a polyfused.
    But you should be able to test the different test-pads.

  5. #5
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by dbhale1943 View Post
    Today, while USB connected, the 5 volt pin was within spec, but the USB current read zero. No LED lights up. The 3V pin read 0 volts. Tried the reset button. Then even tried grounding the program pin for >15 seconds.

    So I am guessing this T4 now has a bad 3.3V regulator.
    I am thinking that there is nothing more to try. Any more suggestions would be appreciated.
    Teensy 4.0 has a power management feature which turns off the 3.3V regulator. Maybe that's why you're seeing 0 volts on the 3.3V pin?

    The On/Off pin is meant to trigger this feature. Holding the pin low for 5+ seconds is supposed to turn the power off. A low at that pin for half a second is supposed to turn the 3.3V power back on.

  6. #6
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    Thanks WMXZ for the info. Also thank you Paul.
    (A belated congratulations on this remarkable Teensy 4.0 product's release to your whole team !)
    I am now more encouraged to get my digital synthesizer ideas from about 50 years ago into this project for sharing, soon.
    I never thought such a fast Teensy product would be possible with a small size and at a low cost.
    My first synthesizer's state of the art device were 64 bit rams at about $8 each. (Inflation would make it ~ $38 today!)
    My synth was enclosed in a wood box which weighed about 40 or 50 pounds and that did not include the Computer Automation 8K core memory minicomputer to drive it.

    It may take a day or so before I can do more testing.

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