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Trying to fix board

Discussion in 'Troubleshooting and Repair' started by Chura, Sep 16, 2012.

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  1. Chura


    Sep 16, 2012
    Hi Guys,

    I wanna practice some of my knowldge and learn abit electronic
    i took a circuit who used to work few years ago and died on me.

    i connect 5V DC 1.2A to it as adapter (i replaced few, adapter is good :))
    attached some photos.

    With multimeter i get bridge to all positive and negative, now i should check the Cap for the written voltages ? (top 3 at 16v 330microf and two lower at 6.3v 1000microf)


    Attached Files:

  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    The voltage on the capacitors is the rated voltage. The operating voltage is lower than that. The exact value the voltage shall have you can get only from the schematic or a (very good) description of the circuit.
    Start by measuring the voltages and report your results. Also measure not only DC but make a second measurement using the AC range of the multimeter. A common failure of electrolytic capcitors is loss of capacitance which will show as a rather large AC component of the voltage across the capacitor.
    In case you have access to an oscilloscope use that to visualize the voltage across the caps.
  3. Rleo6965


    Jan 22, 2012
    The board your fixing looks like LAN router or hub and use +5V to supply its IC. Check the 2 lower capacitors for +5V reading. Usually LAN board have LED indicators. You can use this LED to indentify problem of board.
    Last edited: Sep 18, 2012
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