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RC Transmitter Wont turn on

Discussion in 'Troubleshooting and Repair' started by almunro, Oct 28, 2013.

  1. almunro

    almunro

    2
    0
    Oct 28, 2013
    I have a Walkera Devo 7E that started to play up and now wont stay on. The lcd flashes for a split second when i turn it on but nothing after that. It started by turning on for a few seconds and then turning off, but has progressed its current state.

    Here is a picture of the board.

    [​IMG]

    There was a tiny puff of smoke from what i thought was the crystal, however might have been the capacitor circled? Im not sure f the cap has burnt its top by itself or that was from my soldering iron touching it.

    Would replacing all or some of the caps be a start to fixing the power up issue?

    Thanks for any help.

    Alex
     
  2. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,266
    Nov 28, 2011
    The smoke would not have come from the crystal, nor probably from the electrolytic. The melted plastic looks like it's from a soldering iron.

    What have you been soldering on the board?

    No, capacitor problems are only common in high-energy circuits like TV sets and switching power supplies.

    I would start by cleaning all the flux around the areas you've been soldering, using isopropyl alcohol and a cotton swab, then have a good look over the board to see if any components or tracks have been damaged by excess heat.

    Post complete pictures of both sides of the board and highlight any components or areas that look at all suspicious.

    Do you have access to a service manual or a schematic diagram?
     
  3. almunro

    almunro

    2
    0
    Oct 28, 2013
    The tx rf module is the same as a full range one except for a diode, so if you short the diode the range is extended to normal. I tried soldering it but its too small so i used conductive glue. It seemed to work as it should but started to play up and now wont work.

    Although you said smoke woudnt come from a crystal on closer inspection Ive found a small melt/burn mark on the bottom of the crystal as seen in this picture:

    [​IMG]


    Heres the board, the diode to be shorted is next to the crystal on the right. At the present moment the tx wont turn on but i get a flicker of the lcd when i turn on the switch.

    [​IMG]

    I dont have the schematic sorry.
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,266
    Nov 28, 2011
    The mark on the crystal would have been made from outside.

    Without any technical information it's hard to know where to start.

    I would first suspect any areas where you've done work on it. I would do a careful visual inspection of those areas and the whole unit.

    If you can post all the markings on the MCU (the large four-sided flat device with ARM printed on it) we can find the data sheet so you can check whether there's power on it; that would be the next step. But I think it's unlikely you'll be able to fix it unless you can find service information, and even then there's no guarantee.
     
  5. Six_Shooter

    Six_Shooter

    98
    0
    Nov 16, 2012
    Why has the daughter board been removed?
     
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