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Thread: Scorching hot Propshield

  1. #1

    Scorching hot Propshield

    I have a propshield that after a weeks worth of use the audio went south and the amplifer gets scorching hot.
    I assumed I had done something odd to it so I got a brand new one, soldered a (brand new) teensy 3.2 to it (after I had cut the USB 5V trace) and went to program it.
    and... my bench power supply went into current limiting mode (3 amps) and the audio chip got scorching hot immediately.
    No code had been even downloaded yet and foom! extra toasty!

    I saw that some people were having similar problems a few months back but I saw not sign of a real cause or solution...
    Is there any new news on this front???




    --mjlg

  2. #2
    Senior Member+ defragster's Avatar
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    I have a prop shield LC that the AMP got hot in the seconds after enabling it. This started after minimal use and just adding minimal pins and putting it stand alone on a breadboard to test wired to Teensy. I never got any feedback or resolution - though I had not seen other posts go by with similar problems.

    Is yours the AllOn or the LC version?

    I used a Beta AllOn Prop with no issues - more with the Motion doing feedback through LED string, and I got another Prop_LC that works without any trouble.
    Last edited by defragster; 10-10-2018 at 07:31 AM.

  3. #3
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    I came here looking for answers to this problem. I have burned out 3 Prop Shield LC amps and I have no idea how. Same symptoms as above, power up, fooomp - done. No more amp. On the upside the RAW files stored still played through the DAC to an external amp, but it sort of defeated the purpose.

    I have a 4th Prop Shield LC, so far I have not had the amp burn out or get hot. Was (is?) there a flaw in these boards?

  4. #4
    Senior Member+ mjs513's Avatar
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    Quote Originally Posted by ScottM25 View Post
    I came here looking for answers to this problem. I have burned out 3 Prop Shield LC amps and I have no idea how. Same symptoms as above, power up, fooomp - done. No more amp. On the upside the RAW files stored still played through the DAC to an external amp, but it sort of defeated the purpose.

    I have a 4th Prop Shield LC, so far I have not had the amp burn out or get hot. Was (is?) there a flaw in these boards?
    Might help if you showed how you are connecting the propshield to the LC. Are you sure you are not putting power to ground or something like that. You can get answers if you give us some more details on wiring, whats connected to the prophield, how you powering the propshield/lc etc....

  5. #5
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    Literally just connecting it how it's supposed to, and powering it up with the USB cable. The "burn-out" happened while learning how to use these. I loaded the RAW files with teensytransfer, ran the Frank Boesing file payer examples and eventually the amps burnt up.

    This is a current pic that functions well so far, and an example of what I've done. The wires coming out are connected to the pads on the backside of the Teensy 3.2 going out to an OLED screen.

    Click image for larger version. 

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  6. #6
    Senior Member+ mjs513's Avatar
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    Quote Originally Posted by ScottM25 View Post
    Literally just connecting it how it's supposed to, and powering it up with the USB cable. The "burn-out" happened while learning how to use these. I loaded the RAW files with teensytransfer, ran the Frank Boesing file payer examples and eventually the amps burnt up.

    This is a current pic that functions well so far, and an example of what I've done. The wires coming out are connected to the pads on the backside of the Teensy 3.2 going out to an OLED screen.

    Click image for larger version. 

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ID:	29115
    You sure the problem is not a short on the wires to the oled - not sure how you are powering the OLED. I would start there and do a double check. That is about the only thing I can think of at this point.

  7. #7
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    Yeah, for sure. I had issues without even having the OLED hooked up. And as stated earlier, this set up is actually working great right now. There is no heat on the backside of the Prop Shield at all. I appreciate your replies.

    Besides a physical hardware short or something, is it possible to do something wrong programmatically to fry the amp? For example having a digitalWrite(AMP_ENABLE, HIGH) but not having a corresponding "LOW" write? That's about the only thing I can think of that I might have done wrong.

  8. #8
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by ScottM25 View Post
    Was (is?) there a flaw in these boards?
    I'm not aware of any production flaws or problems. I can tell you every board was tested with a sine wave diving a 10 ohm resistor in the test fixture, though the test lasts only about 1 second.

    If you believe it's a manufacturing defect, we could send you replacement boards. None are left with the motion sensors, only the "LC" ones are in stock.


    Quote Originally Posted by ScottM25 View Post
    is it possible to do something wrong programmatically to fry the amp? For example having a digitalWrite(AMP_ENABLE, HIGH) but not having a corresponding "LOW" write?
    That really shouldn't matter. Even if the pin "floats" the Prop Shield has a pulldown resistor to keep the amp turned off until your code drives the pin high.

  9. #9
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    Thank you for the reply, Paul. I've always been impressed how active you are here, and how much you stand behind what you've created.

    Which, btw, I absolutely love this platform. Thank you for creating it.

    I asked the question about flaws because the first two posts in this thread were a few years old and I was curious if anything had come up since. Having a similar problem as others have had in the past lends itself to something common we all did to invoke the issue. Or the problem was built in and something we did brought it out. I have no idea really. I wish I had kept better track of what I was doing when I was first learning how to use the Teensy and Prop Shield LC combo.

    I appreciate the offer to replace, but I no longer have the first 2 Prop Shields where the amp got hot and stopped working. I used the ram storage and the ability to access and stream via the DAC output to an external amp and they are not in my possession. I do still have one with a blown amp, I don't know if you could do any kind of "autopsy" on it or not.

    Again, thanks for the reply and thanks for making these.

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