Impedance transformer...HELP!!

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by HawkeyeKane, Jan 18, 2015.

  1. HawkeyeKane

    HawkeyeKane Member

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    I'm trying to wire this little impedance transformer into a circuit to take a hi-Z signal and convert it to a low-Z input. It should go from 50K ohms to about 500 ohms. I pulled it out of an old Archer brand inline adapter that went from XLR female to 1/4" male. But I can't remember how it was wired and I can't find the adapter housing anywhere. I haven't found any transformers online that have these color wires. Anyone have an idea? I need to get this project wrapped up ASAP!

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  2. mark norwine

    mark norwine Member

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    well, for starters, it should be an isolation transformer, meaning "the primary doesn't electrically 'touch' the secondary". So to begin with, use an ohm meter to figure which leads are paired up. One pair will be the primary, the other pair is the secondary.

    From there, you'll need a steady, accurate low-voltage ac source...with which you'll do the following:

    - apply a small-but-steady measured ac voltage to one of the pairs of leads. We'll call this "winding A". Hook up a meter to monitor this voltage & leave it there. Apply about 2 volts...not much more.

    - WITHOUT TOUCHING THE OTHER LEADS, take another meter and measure the ac voltage of "winding B"....it will either be much higher or much lower.

    .....if winding B is higher....good. This is the Hi Z side and, by default, winding A is the low Z side. Measure the voltage on B, then skip to part 2

    .....if winding B is lower...stop. This (B) is the Low Z side. Disconnect the small ac voltage on A and apply it to B, confirming that it's still about 2 volts. Measure A. Skip to part 2

    Part 2: you now have a measured low voltage (about 2 volts) on the Low Z side. You are now measuring the higher voltage on the High Z side.

    Divide the High Z voltage by the Low Z voltage. That's the turns ratio. Square this number, and that's your Z ratio.

    Make sense?
     
  3. J M Fahey

    J M Fahey Member

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    Agree and add: just to know which is which, measure each winding DC resistance; one of them will be at least 10X that of the other, that's the high impedance one.

    Think, say, >600 ohms vs. <20 ohms or thereabout.
     
  4. mark norwine

    mark norwine Member

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    it's one of the biggest frustrations of TGP.....someone cries out for immediate help to solve an immediate problem....

    You offer an answer....in 13 minutes, no less....you give specific knowledge....

    ....and you hear nothing.

    Did it work? Did it help?

    Just silence.....
     
  5. J M Fahey

    J M Fahey Member

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  6. HawkeyeKane

    HawkeyeKane Member

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    Apologies. Been really busy with lots of projects and divorce proceedings.

    I hooked it up to a multimeter and it gave no readout. So I'm guessing its dead.
     
  7. DGDGBD

    DGDGBD Member

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    Every so often I will try to gain knowledge on a tech problem by searching the TGP archives. I see posts like the one from Mark, and from other trained electronics techs, and they are always a big help. So, a big Thank You to Mark and others who know their sh*t and are willing to share their knowledge with the masses!
     
  8. J M Fahey

    J M Fahey Member

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    Sorry to hear that, hope it improves .

    "no readout" is not a measurement :eek:

    Set multimeter to resistance scale, try the 20k ohms and the 200 ohms ones, and measure every wire against all others.

    You "should" read something.
    I suggested some values to be expected.

    Post results, stating which wire measures what against another.

    Of course, blank scale or a "1" reading with all other digits blank means "open" or "out of scale" .

    Good luck.
     

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