NR7101 Dead

Pioneer
Pioneer Posts: 8  Freshman Member
First Comment
in Mobile Broadband

Sudden failure of NR7101. New POE or Ethernet cable do not fix the issue.
no light comes on. No LAN connectivity. Warranty seems to have only been 2 years (looking at support website).
therefore I’ve inspected device. Seems the heatsink medium has come away from aluminium blocks so I suspect a hardware failure due to overheating. Would like to attempt a repair if anyone can help (I’m an engineer).

All Replies

  • n_o
    n_o Posts: 64  Ally Member
    First Comment Friend Collector Second Anniversary

    do you have a TTL adapter ?
    i would start there , see if it tries to boot

  • Pioneer
    Pioneer Posts: 8  Freshman Member
    First Comment

    I don’t. Something like this? https://thepihut.com/products/usb-to-ttl-serial-cable-debug-console-cable-for-raspberry-pi?

  • Pioneer
    Pioneer Posts: 8  Freshman Member
    First Comment

    I would benefit from some guidance on how to correctly use the cable to check functionality. E.g. what software would I run?

    Thank you

  • Pioneer
    Pioneer Posts: 8  Freshman Member
    First Comment
    edited February 4

    Found the open source info with help of chatGPT. Going to use that: https://openwrt.org/toh/zyxel/nr7101?utm_source=chatgpt.com

  • DOES
    DOES Posts: 6  Freshman Member
    First Comment Friend Collector

    apparently there is a range of serials with faulty Poe circuitry… if you open the antenna there are 12v solder points (for a barrel connector) next to the Ethernet connector.

  • Pioneer
    Pioneer Posts: 8  Freshman Member
    First Comment

    I’ve isolated the fault to one of these components shorting to ground

    IMG_7478.jpeg
  • Pioneer
    Pioneer Posts: 8  Freshman Member
    First Comment
    edited February 8

    Need help on which component to try replacing (so small I don’t want to start desoldering to work out which is causing fault to ground).

  • Arona
    Arona Posts: 23  Freshman Member
    First Comment Friend Collector

    here to see if you find a solution since i think i have similar problem on the nr7101 as well.

  • Pioneer
    Pioneer Posts: 8  Freshman Member
    First Comment




    WINNER!!
    I've replaced MOSFET Q1 with IRLML0060 N-Channel 60V 2.7A SOT-23. Bit of a guess as there was no part number on the one removed. However, I have an oscilloscope and measured the voltage at 50Vac input, and the router should use about 1A continuous max.
    The root cause appears to be the heatsink material on the back of the are where the MOSFET is mounted. A bit too much clearance meant there wasn't a solid interface.
    Fingers crossed for many more years' of use.

    IMG_7478.jpeg
    IMG_7511.jpeg
    IMG_7510.jpeg

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