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Overheating Cable Modem

Discussion in 'Electronic Repair' started by Johnny Public, Mar 20, 2006.

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  1. Hi,

    I have a Terayon TJ 715X Cable Modem that I received when I got my Cox
    account. It has worked fine for about 14 months but lately I have been
    getting a strange problem. The "Cable" light will stop being solid and
    then start blinking slowly for hours. During that time I have no
    internet. If I leave the modem unplugged from power for about two hours
    it will work but usually returns.
    I took it apart today and touched the Coaxial RF-In "box" and it was
    VERY warm. I blew on it for about a minute and when it was cooler
    reassembled the modem and connected everything. It started up and
    connected to the internet very quickly.
    I figured the casing was too restrictive so I cut the plastic above the
    RF thing out of the case. It was working for about 20 minutes and then
    stopped again. The back of where I cut felt hot. I took the entire thing
    Right now as I write here is the situation: The modem board is encased
    in a thin metal that goes around it. The way it was put together was
    there is a plastic case, and that is in two pieces. Each piece has a
    thin metal half. When the plastic is put together the inner metal case
    touches. The modem board is inside that.
    The modem is open and on my desk next to me. I left it in the metal case
    but have removed the plastic case. All is fine so far but I was
    wondering if there is any danger to me?
    Until I can get a small fan to run through the plastic case I need to
    let it sit out. Can it, while operating, leak any waves that can be
    harmful. I know that microwaves are bad and read that when making a
    "cantenna" for a wifi setup not to look into it while it is operating
    cause that could hurt you.

    Any help, ideas or suggestions on anything I wrote would be appreciated.


  2. Ivan

    Ivan Guest

    Why can't you just contact the cable company and get them to replace the
  3. They're making these modems might cheap nowadays.

    First make sure you have the right AC adapter! One of too high a
    voltage will cause the modem to overheat. Then blow any dust out of the
    ventilation holes. Don't set the modem on a thick rug as that will
    block the vent holes. Don't run the modem on its side, it needs the
    holes at the top and bottom for convection.

    Then check to see if any heatsinks have fallen off the chips. These
    are stuck-on nowadays with a little double-sided tape. Sometimes these
    fall off for various reasons. They also slide off if you operate the
    modem or router at an unusual angle!
  4. Jerry G.

    Jerry G. Guest

    Call the cable company for a replacement, rather than having something
    that will soon fail, and you will have no service.

    Jerry G.
  5. James Sweet

    James Sweet Guest

    You could check for any cracked solder joints but I would probably just
    replace the modem unless you're looking for a challenge. They're pretty
  6. Franc Zabkar

    Franc Zabkar Guest

    AFAIK, these modems tend to use onboard switchmode regulators, so
    overheating in the power supply may not be a real concern. Instead I'd
    be adding heatsinks to the bigger chips and drilling more vent holes.

    - Franc Zabkar
  7. Ivan,

    I initially thought that it was their cable line that was causing the
    problem. I called and set up and appointment for them to come out and
    when I spoke with the customer service rep they said that if it isn't
    the line it would be $49.95 for the tech. If it was the modem I would be
    charged the $49.95 for the tech and then $50 for a new modem. I bought
    the modem when I started service with them (Cox Cable) and am not
    leasing it. Therefore they say it is my property and equipment.

  8. Guest

    May be bad or leaky capacitors. I saw it once. What brand of capacitor
    is used in the modem? If it is a notorious one, you can replace it and
    see what happen
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