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Help Identifying SMD diode

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  • #1

    Help Identifying SMD diode

    I got this pedal and it won't power. Guy I got it form said he used the wrong voltage power supply. D6 tested to be shorted. All I can see is the label which is "5A9D." I've looked up some info online and got a lot of different identifiers from "5A." The pedal is a KMA Horizont Phaser. No schematic info online.

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  • #2
    I would think it is a 9V zener. Does anode end go to ground? Looks like the pedal runs on (-)9V supply, zener goes from supply to ground, D1 is series diode allowing only (-) voltage through.
    Originally posted by Enzo
    I have a sign in my shop that says, "Never think up reasons not to check something."


    ​

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    • #3
      Yeah, the anode goes to ground. I tried a 9.1v 1W Zener and no luck.

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      • #4
        What voltage do you measure across the replacement zener?
        "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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        • #5
          Am I correct, you replaced a shorted diode, and the diode had shorted because wrong power was applied? The diode is there to protect the circuit, but in the process of killing the diode, further damage may have been done to the circuit. Look beyond the diode.
          Education is what you're left with after you have forgotten what you have learned.

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          • #6
            Remove the diode and feed pedal real 9V from a wall wart (measure it first) and double check you have the right polarity because you just removed the protection diode.
            Does it work now?

            Many pedals have a simple cheap "suicide" protection in the form of a 1N4002 or similar diode across the power jack, reverse polarity of course, so in normal use it passes no current.

            If you reverse polarity, diode straight shorts wall wart ,protecting pedal but often dying itself.
            IF thatīs the case, replace it by an SMT 1N4002

            And why not a series diode instead?

            9V is allready a very low supply voltage, losing 0.7V across a series diode IS a big deal, parallel reverse diode drops nothing unless needed.
            Juan Manuel Fahey
            • Likes 1

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            • #7
              Originally posted by Enzo View Post
              Am I correct, you replaced a shorted diode, and the diode had shorted because wrong power was applied? The diode is there to protect the circuit, but in the process of killing the diode, further damage may have been done to the circuit. Look beyond the diode.
              I'm not getting any voltage. I'm not sure if the cathode of the 9v Zener is supposed to go to the 9v PS input but it is not that way if I trace the circuit.

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              • #8
                I removed R22 and put a jumper and the connected the cathode of D6 to the 9v supply and it’s working.

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