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Discussion in 'Electronic Repair' started by GregS, Apr 28, 2009.

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  1. GregS

    GregS Guest

    Got a Dell computer with something called a 110 Twin Alert.
    This little board on the top of the chassis is shutting down the power
    supply. I thought it might have been some kind of temperature
    alert gone bad. Got Got some power circuitry with a beeper.

  2. Franc Zabkar

    Franc Zabkar Guest

    Could it be this warning device with a 110dBa sounder and a low
    wattage speaker? TwinA.pdf

    The pinouts are:

    Symbol Description
    - 0V
    + 12V
    BA Siren Trigger
    SPK Speaker
    T Tamper
    T Tamper

    I can't see how it would be responsible for shutting down your power
    supply, though.

    - Franc Zabkar
  3. GregS

    GregS Guest

    Thats was interesting.
    I will post a picture later.

  4. GregS

    GregS Guest

    So here is a picture. I think its just a temp warning beeper that went bad and shorting out
    supply. Weird.

  5. Franc Zabkar

    Franc Zabkar Guest

    It looks like the Pyronix device is something completely different.
    How do both trademarks coexist ???

    Here is a PC Power & Cooling alarm that is similar to yours.

    110 Alert Heat Alarm:

    It is set to go off when the temperature reaches 110 deg F. It doesn't
    appear to do anything other than alert the user, though.

    OTOH your device appears to shut down the PSU. You can see the
    thermistor below the second M in the LM339M quad comparator. Could
    that be a crowbar SCR across the +12V or +5V input? What are the two
    large parts at the RHS of the PCB?

    The only useful reference I can find to TwinAlert with Google is this

    This is a Google translation:
    Sensory devices for heat

    Thus, this problem could be avoided entirely by using the company's
    110 Twinalert PC Power and Cooling Systems. Twinalert represents 110
    bus to the size of a credit card that is connected to the plug such as
    power flopito. When the temperature in the PC-it reaches 43 degrees,
    the device starts to squeak, creating annoying noise, and in 47
    degrees just excludes computer. It cost under $ 50 ...

    - Franc Zabkar
  6. Eeyore

    Eeyore Guest

    LM339 is a quad comparator. The board is also legended 'power and cooling'. I'd guess it
    monitors temp and several supplies.

  7. Bob Larter

    Bob Larter Guest

    It looks like it's monitoring the temperature (there's a thermistor on
    the bottom right of the PCB). I notice that it has a local regulator,
    which I'd be guessing is a 7805 that's shorted out.
  8. Franc Zabkar

    Franc Zabkar Guest

    The pinout for a 7805, from top to bottom, is "In Gnd Out". This
    doesn't fit with the "+12V Gnd Gnd +5V" pinout of a drive connector.
    In any case why would you need a local +5V regulator when the incoming
    supply already provides +5V? If for some reason you did need a +5V
    regulator, then wouldn't a 78L05 be adequate for this circuit?

    - Franc Zabkar
  9. Eeyore

    Eeyore Guest

    That heatinked device seems rather odd, not least the way it's mounted with
    bent leads.

  10. Bob Larter

    Bob Larter Guest

    <looks again>

    Yeah, you're right about it not being a 78xx reg. I must've been a bit
    slydexic when I first looked at it.
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