Phantom Triggering

Discussion in 'AV Receivers' started by Grant B, May 28, 2003.

  1. Grant B

    Grant B Producer

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    I use a parasound scamp to turn on my amps and a 12v wallwart trigger from my Sony TAE 9000ES Preamp. Lately the amps have been turning on without the preamp. I have the preamp on a tripplite ups which cleared up earlier problems with flucations in my AC power.
    ANy ideas /suggestions?
    Thanks
    Grant
     
  2. NickSP

    NickSP Supporting Actor

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    UH, never mind the "Wallwart" question i originally asked [​IMG]
     
  3. Jonathan M

    Jonathan M Second Unit

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    Am I right in assuming the wallwart 12V power pack is plugged into the switched output of the preamp, and the 12V out of the power pack is plugged into the Parasound scamp? If not, how is it hooked up?

    The 12V trigger circuits are really simple. Basically the 12V enters a resistor which sets the current level (Usually very low like 1mA or less) needed to saturate a transistor. The transistor turns on fully and causes current from a 12V source in the switching unit to flow through a relay, thus turning the appliance on. If it's triggering when it's not supposed to, then there is a small amount of current getting through to switch the transistor on, or there is a fault somewhere.

    One option is to try a lower voltage wallwart - ie try a 6V or 9V one if you have one handy. This will lower the amount of current feeding the bass of the transistor, so will lower the chance of it switching accidently. Another option is to feed the 12V through a current limiting resistor (a 25k pot is ideal) to vary the amount of current fed into the switching unit. You should be able to vary the pot to find a level where it'll switch on when it should, but won't switch on when it shouldn't. What MAY be happening is that many 12V wallwarts actually put out more than 12V DC when unloaded (Which is what it'll be when just acting as the trigger source) - I have one here rated at 600mA, yet when running a trigger circuit which only needs 1mA or less, it's putting out 20V or so.

    Hope this helps
     
  4. Grant B

    Grant B Producer

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    Johnathon
    Many thanks! I will try that
    Grant
     

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