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  1. #1
    Join Date
    9th August 2009
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    Blacksburg, Virginia
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    740

    Eggfinder mini overheating?

    I recently built an eggfinder mini and tested it to be working quite well. I took it out of my rocket box a couple months later to show a friend and, while it wouldn't power up, it got hot. I mean too-hot-to-touch on the center pin of the GPS module and the diode at the power point. Has this happened to anyone? There doesn't appear to be any physical damage or change since it was working, and the battery connection and everything is identical. Is there a logical place to start looking, or test points I should check to see if something is straight-up fried?

    Jordan
    TRA Level 3
    NRVR

  2. #2
    Join Date
    22nd January 2017
    Location
    North Florida
    Posts
    54
    What type of battery are you using?

    -Dave
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    Level 1 - PML AMRAAM 2
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  3. #3
    Join Date
    18th March 2009
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    Wisconsin
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    3,830
    Do you have a short somewhere? A soldier bridge of something like that?


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    Mark Koelsch
    Tripoli 6155 L3
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  4. #4
    Join Date
    26th November 2009
    Posts
    5,246
    Not good. I had a "bad"Quantum I suspect a bridge under the Wifi chip so it resides in the junk drawer. The VR chip got super hot. Kurt

  5. #5
    Join Date
    3rd February 2012
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    Chances are that you got a solder bridge somewhere, possibly under the RF module. That's why I put a step in the assembly instructions to put a piece of paper masking tape under the RF module and trim it to the edges. If it's a dead short between power and ground, the Mini "will" work, but it's going to suck a lot of power out of the battery, possibly overloading the regulator. Worst case, that can lead to a regulator failure, which might send the full battery voltage to your GPS and RF modules. That's a bad thing... they will fry for sure. I would recommend carefully unsoldering the RF module and looking for anything that might be causing a problem.

  6. #6
    Join Date
    9th August 2009
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    Blacksburg, Virginia
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    Thanks for the replies - I've been afk for a bit due to work. I've also just gotten a new multimeter (the old one died) and will be be able to check some test points. Battery is a 2s lipo, good voltage on both cells with two testers, that isn't overheating or appearing to have any other issue.

    I will double check the RF module. Edit - I subbed electrical - tape for the masking under the RF module as I was concerned about long term stability of masking tape, but that shouldn't be the problem.

    The thing that's bugging me is that it managed to checkout fine after assembly. I even set it on my deck and drove around the neighborhood to see what kind of range I could expect and how it compared to my 70cm GPS unit. I've been trying to think what could have caused a good unit to go short and all I can think is that shrink-wrapping the battery to the board might have compressed something.

    Hopefully I'll get to do a checkout this weekend and will report back if I find where it went of the rails. Thanks again!
    Last edited by JordanT; 6th May 2018 at 01:27 PM.
    Jordan
    TRA Level 3
    NRVR

  7. #7
    Join Date
    9th August 2009
    Location
    Blacksburg, Virginia
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    740
    Quote Originally Posted by cerving View Post
    Chances are that you got a solder bridge somewhere, possibly under the RF module. That's why I put a step in the assembly instructions to put a piece of paper masking tape under the RF module and trim it to the edges. If it's a dead short between power and ground, the Mini "will" work, but it's going to suck a lot of power out of the battery, possibly overloading the regulator. Worst case, that can lead to a regulator failure, which might send the full battery voltage to your GPS and RF modules. That's a bad thing... they will fry for sure. I would recommend carefully unsoldering the RF module and looking for anything that might be causing a problem.
    The tape under the RF module looked fine (it was electrical though, not masking). I damaged most of the solder pads beyond repair during disassembly, but went ahead and tried a couple power tests. I put 7.8v on the board without the RF module and it drew 6-8mA. I put 3.3v on the RF module and it drew 250ma and the IC on the module got too hot to touch in a bit over 10 seconds. There was no visible physical damage to any of the chips. I'm at a bit of a loss for chasing down anything else, and I think I'll just order another and chalk it up to experience.
    Jordan
    TRA Level 3
    NRVR

  8. #8
    Join Date
    26th November 2009
    Posts
    5,246
    Quote Originally Posted by JordanT View Post
    The tape under the RF module looked fine (it was electrical though, not masking). I damaged most of the solder pads beyond repair during disassembly, but went ahead and tried a couple power tests. I put 7.8v on the board without the RF module and it drew 6-8mA. I put 3.3v on the RF module and it drew 250ma and the IC on the module got too hot to touch in a bit over 10 seconds. There was no visible physical damage to any of the chips. I'm at a bit of a loss for chasing down anything else, and I think I'll just order another and chalk it up to experience.
    Good idea. I have a few items in a junk cup in case I need a push button switch or LED off a dead board. You can wrack yourself trying to fix some of this stuff and it's not worth your time. Yeah, if you have a few thousands of dollars worth of SMT "diddling" equipment a piece o' cake but sometimes one just has to cut their loses.

    Geez, there's a video out there of a guy who obviously has invested a pile of money in a soldering station and microscope who put 64Gb of memory on the OOP Nexus 7 2013. I can't find the vid at the moment but a Russian guy did it too. Kurt

  9. #9
    Join Date
    3rd February 2012
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    FYI, it's not unusual for the regulator IC to get warm... it basically dissipates the power difference between the input and output power as heat. It's rated to about 1A and 16V input, although the Eggfinder circuitry itself only draws about 70 mA, so a 2S LiPo can be expected to dissipate about (7.8V - 3.3V) * .070A, or about .32W. That's not a lot, but a short will send that way up. The operational junction temperature on the regulator is rated to 125C, so it can easily be hot to the touch without being a problem.

    If the RF Module or GPS Module, or any other component on the board for that matter, is hot to the touch... well, that's a problem.

  10. #10
    Join Date
    9th August 2009
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    Blacksburg, Virginia
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    740
    Yeah, what keeps tripping me up is that it worked 100% after I'd finished it. It was 2 months later when I got it out for a demo that it would no longer show that it was activated (no lights on the unit at all) and the extra heat, esp in the RF board IC. It's really NBD; besides, the second one is always faster to assemble. ;-)

    Jordan
    TRA Level 3
    NRVR

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