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Thread: New Build: Not getting 5V or 3.3V

  1. #1
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    New Build: Not getting 5V or 3.3V

    Hi

    I recently completed my HM 4.3.4. I connect my Pi Zero W to it yesterday both with 12v and USB. It booted right up.

    Today, I was starting to work with it again and it fried my Pi Zero. I then check the 5V points and I'm getting 10v. On my 3V points Im getting 6V.

    Any help of where to start would be great!

    Base board pictures: https://imgur.com/a/8mUI2yN

  2. #2
    TVWBB Honor Circle Bryan Mayland's Avatar
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    Well, all the parts look to be in the right place, apart from missing a 100k resistor by the pit probe jack. A picture of the solder side of the board too would be useful, unless I'm missing a way here to get to another image. I'm not sure how you could end up with 10V on the 5V unless something backfed 12V through the 5V regulator... which still wouldn't cause the 3.3V bits to be 6V (since that should be fine taking 10V down to 3.3V by itself). I think you're going to have to start pulling parts off until voltages start looking right on the PCB. The ATmega can come out (which also might be fried since its Maximum Operating Voltage is 6V), but that's probably not going to change anything since it doesn't drive any of the supply voltages.
    I'm that HeaterMeter guy what ruins everybody's free time.

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    Thanks for the quick reply.

    Concerning, the 100k resistor - is the required even if using the thermoristor? The instructions made it sound like it was 10K for Thermoristor or 100k for thermocouple (not both)

    Opps, looks like the solder side didn't upload, here it is: https://imgur.com/a/VYlE5iW Excuse the long cut offs - I need a new cutter

    Guess what, I just took the ATmega off and reseated it. I'm getting the right voltage now. I'm not sure if my multimeter just gave a wrong reading or something.

  4. #4
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    Thermistor probes need both the 10k and 100k resistors. The 100k is part of the RC filter circuit and must be present for all probes, the 10K is the pullup resistor that is required for thermistor probes only (thermocouple does not need a pullup resistor)
    I created the Roto Damper, RD3, HMv4.2 sliding back case, "air-burner" and the "ping-pong" valve in my quest for delicious "set and forget" BBQ.

  5. #5
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    Thanks for the info!

    I'll test some more on my board about the voltage. I'm 99% sure this is just me being stupid. I likely had a bad reading from my multi-meter/wrong setting and I likely matted the Pi on the wrong pins which cause it to fry. I don't think there is anything wrong with my board after all.

  6. #6
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    Im at a lose, I fried another Pi Zero.

    I tested the baseboard/LCD only on 12V and all my 5, 3 and 12V points. They all came back good.

    I matted the Pi to the HM and powered the Pi via USB. The HM came up great, every probe worked great, and no issues reported in the GUI.

    When I tried the 12V - the screen came on but the Pi wouldn't boot. Re-tested with the USB and the Pi seems to be dead.

  7. #7
    TVWBB Guru Steve_M's Avatar
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    Did you check the voltages on all of the RasPi header pins when the HM is powered up via 12v to ensure than only 5v is going to the 2 x 5v pins on the RasPi header?

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    Yes I tested the Pi two 5V and G25 (3.3) points and they came back normal.

    For what itís worth when powering the Pi via USB. The LCD lights up and works as expected.

  9. #9
    TVWBB Honor Circle Bryan Mayland's Avatar
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    Have you checked the HeaterMeter base board just by itself, powered with 12V and go through every one of the RPi header pins on it and check them for weird voltages? We should only be supplying 5V on those two bottom right pins, and then only the RXD, TXD, SCK, MIS, MOS, and G25 are connected. The rest should just be floating or GND. Nothing higher than 3.3V on those listed pins, apart from the 2x 5V pins.
    I'm that HeaterMeter guy what ruins everybody's free time.

  10. #10
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    Quote Originally Posted by Bryan Mayland View Post
    Have you checked the HeaterMeter base board just by itself, powered with 12V and go through every one of the RPi header pins on it and check them for weird voltages? We should only be supplying 5V on those two bottom right pins, and then only the RXD, TXD, SCK, MIS, MOS, and G25 are connected. The rest should just be floating or GND. Nothing higher than 3.3V on those listed pins, apart from the 2x 5V pins.
    With baseboard only on 12v - I did not see anything other than 5 and 3.3. (on the Pi connector)

    Am I suppose to be seeing something on SCK and MIS? Or are you just saying that's the only PIN actually connected.
    Last edited by KevinL; 07-22-2019 at 09:13 AM.

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