C-Touch burned

Discussion in 'C-Bus Wired Hardware' started by Darpa, Sep 2, 2007.

  1. Darpa

    Darpa

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    From the sounds of things Nick, someone has definately connected something OTHER than a pink c-bus cable to those terminals. The whole point of a diode for protection is to prevent power flowing the wrong way, and I really can't see how connecting C-Bus the wrong way round would blow the damn diode up :confused:
    I think Tobex's suggestion of DC or possibly even something stupid like mains was connected to it, as thats the only time I've seen a diode self-destruct like that (except for maybe once when I had a customer connect a 12v touch-screen for a car in reverse polarity, and the main protection diode in that let out its magic smoke :rolleyes: )
    I definately wouldn't be allowing a warranty claim on the C-touch if I was the one who made that decision...
     
    Darpa, Sep 2, 2007
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  2. Darpa

    NickD Moderator

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    Actually the diodes you can see there are zener diodes, there to protect against overvoltage on the bus, and the blue disc you can see in the picture is a PTC resistor, to protect against reverse connection.

    The small chip component hidden amidst the carnage is a ferrite bead, which looks the worst of the lot, is in the circuit between the negative bus terminal and the zener. Interestingly there is another one of these in series with the positive terminal (you can see it just below the PTC in the lower pic) which looks perfectly OK, as does the other zener (it looks a bit dull but I think this is just dust).

    Connecting C-Bus to the RS232 port wouldn't do this. My guess is that something (perhaps C-Bus +ve.. if it were 240V I think the results would be a little more spectacular) was shorted to the fascia or the screen. This would bypass the PTC, and only affect the zener and ferrite as seen.

    Nick
     
    NickD, Sep 3, 2007
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  3. Darpa

    Darpa

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    Thank god for the experts on here who can give us our daily feeding of the juicy facts :D

    Although don't you mean "PTC Resistor, to protect against over-current"?
     
    Darpa, Sep 3, 2007
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  4. Darpa

    Hunter

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    My b/w touch screen has always required the programing cable to be physically "lifted" up while transfering programing. It was initially very frustrating, but I am now used to it.
    I have an extension cable built into my wall that when fitted applies an upward pressure on the connection.
    The screen I have was the one I recieved at the intermediate 1 course (November 2006) Several others in the class had a simmilar problem but the cause was thought to be the programming cable rather than the screen.

    I'm not sure if this is related though.
     
    Hunter, Sep 5, 2007
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