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9 parts are printed AA.

Not sure which one you have?

Answer up to 4 quick questions and these 9 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • BCX51SOT-89PNP transistor, 3 pins, Infineon
    What it is
    PNP transistor
    Maker
    Infineon
    Package
    SOT-89
    Pins
    3
    Details
    -45 V, -1 A PNP medium-power transistor
    Source
    From the manufacturer's datasheet

    Is it dead?

    Diode range, part lifted or its base leg off the pad.

    Working, it reads

    Black probe on the base reads about 0.6 to 0.75 V to the emitter and to the collector, and open the other way round. Collector to emitter reads open both ways.

    Dead, it reads

    • Collector to emitter the same both ways, near 0 V with a continuous beep: shorted. The commonest failure.
    • The base the same both ways to another pin, near 0 V or a middling value: a shorted junction.
    • Only one junction reads, or none: a junction has failed open. It then looks like a diode.
    • A reading the wrong way round, where it should be open: leaky.
    On the board:
    On the board this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
    Compare:
    If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
    Watch for:
    A pair of diodes with a common pin reads just like a transistor, and some transistors carry a built-in diode or resistor. The datasheet says which.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • 8 more parts have no package on record. Nothing rules them out, so they stay.
    • AONA66916MOSFET, Alpha & Omega Semiconductor
      What it is
      MOSFET
      Maker
      Alpha & Omega Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Medium-voltage (40-400 V) MOSFET
      Source
      From the manufacturer's datasheet

      Is it dead?

      Diode range, part lifted. Test drain to source first, then short gate to source and test again.

      Working, it reads

      One way between drain and source reads about 0.4 to 0.9 V, the body diode, and the other way open. The gate reads open to both other pins.

      Dead, it reads

      • Drain to source the same both ways, near 0 V with a continuous beep, and still so after shorting gate to source: shorted. The classic failure.
      • The gate reads low to source or drain: gate shorted.
      • No body diode at all: failed open.
      On the board:
      On the board the gate usually has a resistor to the source, which reads as that resistor and is not a fault. Lift a leg to be sure.
      Compare:
      If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
      Watch for:
      The diode range can charge the gate enough to turn the part on, and then drain to source reads near 0 both ways on a good part. Short gate to source and test again before you condemn it.

      A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

    • AONC40202MOSFET, Alpha & Omega Semiconductor
      What it is
      MOSFET
      Maker
      Alpha & Omega Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Low-voltage (12-30 V) MOSFET
      Source
      From the manufacturer's datasheet

      Is it dead?

      Diode range, part lifted. Test drain to source first, then short gate to source and test again.

      Working, it reads

      One way between drain and source reads about 0.4 to 0.9 V, the body diode, and the other way open. The gate reads open to both other pins.

      Dead, it reads

      • Drain to source the same both ways, near 0 V with a continuous beep, and still so after shorting gate to source: shorted. The classic failure.
      • The gate reads low to source or drain: gate shorted.
      • No body diode at all: failed open.
      On the board:
      On the board the gate usually has a resistor to the source, which reads as that resistor and is not a fault. Lift a leg to be sure.
      Compare:
      If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
      Watch for:
      The diode range can charge the gate enough to turn the part on, and then drain to source reads near 0 both ways on a good part. Short gate to source and test again before you condemn it.

      A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

    • AOZ8312DIESD protection diode, Alpha & Omega Semiconductor
      What it is
      ESD protection diode
      Maker
      Alpha & Omega Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      ESD protection for high-speed interfaces
      Source
      From the manufacturer's datasheet

      Is it dead?

      Diode range, from the protected line to ground, part lifted if you can.

      Working, it reads

      A one-way part reads about 0.6 to 0.8 V forward and open in reverse. A two-way part reads open both ways. Arrays with several lines read as the datasheet's diagram draws them.

      Dead, it reads

      • From the line to ground, the same reading both ways, near 0 V with a continuous beep: shorted.
      • A reading both ways on a one-way part: leaky.
      • A one-way part open both ways: failed open.
      On the board:
      On the board, a line reading shorted to ground can be this part or anything else on that line. Lift it: if the short goes with it, it has failed.
      Compare:
      The same part on the next line or connector pin is the healthy reading to compare with.
      Watch for:
      A two-way part reads open both ways when it is good, exactly like one that has failed open. The meter cannot tell them apart; an identical part on the next line can.

      A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

    • BA892Diode, Infineon
      What it is
      Diode
      Maker
      Infineon
      Package
      Not recorded
      Pins
      Not recorded
      Source
      From the manufacturer's datasheet

      Is it dead?

      Diode range, part lifted or one leg off the pad. Red probe on the anode.

      Working, it reads

      About 0.5 to 0.8 V anode to cathode, and open the other way. Small switching diodes read about 0.6 to 0.7 V; large rectifiers can read a little lower.

      Dead, it reads

      • The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
      • Open both ways: failed open.
      • A reading the wrong way round as well: leaky.
      On the board:
      On the board this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
      Compare:
      If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
      Watch for:
      A three-pin body can hold two diodes. With a common pin they read two junctions from that pin, just like a transistor; in series they read two drops end to end. Test each pair the datasheet names.

      A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

    • BA892-02LDiode, Infineon
      What it is
      Diode
      Maker
      Infineon
      Package
      Not recorded
      Pins
      Not recorded
      Source
      From the manufacturer's datasheet

      Is it dead?

      Diode range, part lifted or one leg off the pad. Red probe on the anode.

      Working, it reads

      About 0.5 to 0.8 V anode to cathode, and open the other way. Small switching diodes read about 0.6 to 0.7 V; large rectifiers can read a little lower.

      Dead, it reads

      • The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
      • Open both ways: failed open.
      • A reading the wrong way round as well: leaky.
      On the board:
      On the board this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
      Compare:
      If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
      Watch for:
      A three-pin body can hold two diodes. With a common pin they read two junctions from that pin, just like a transistor; in series they read two drops end to end. Test each pair the datasheet names.

      A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

    • BCW60ATransistor, Infineon
      What it is
      Transistor
      Maker
      Infineon
      Package
      Not recorded
      Pins
      Not recorded
      Source
      From the manufacturer's datasheet

      Is it dead?

      Diode range, part lifted or its base leg off the pad.

      Working, it reads

      From the base, one probe colour reads about 0.6 to 0.75 V to the emitter and to the collector, and open the other way round. Collector to emitter reads open both ways.

      Dead, it reads

      • Collector to emitter the same both ways, near 0 V with a continuous beep: shorted. The commonest failure.
      • The base the same both ways to another pin, near 0 V or a middling value: a shorted junction.
      • Only one junction reads, or none: a junction has failed open. It then looks like a diode.
      • A reading the wrong way round, where it should be open: leaky.
      On the board:
      On the board this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
      Compare:
      If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
      Watch for:
      A pair of diodes with a common pin reads just like a transistor, and some transistors carry a built-in diode or resistor. The datasheet says which.

      A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

    • BZX884B2V4LZener diode, Vishay
      What it is
      Zener diode
      Maker
      Vishay
      Package
      Not recorded
      Pins
      Not recorded
      Details
      2.4 V Zener diode
      Source
      From the manufacturer's datasheet

      Is it dead?

      Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.

      Working, it reads

      About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.

      Dead, it reads

      • The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
      • Open both ways, forward too: failed open.
      • Holds well off its rated voltage on the supply test: drifted.
      • A soft knee, or a voltage that creeps on the supply test: leaky.
      On the board:
      On the board this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
      Compare:
      If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
      Watch for:
      A meter's diode range stops at about 2 to 3 V, so almost every Zener reads open in reverse on it, good or bad; a 3 V meter may just show a 2.4 or 2.7 V part. Above about 3 V the meter cannot tell a Zener from a plain diode.

      A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

    • ESD218-B1-02ELESD protection diode, Infineon
      What it is
      ESD protection diode
      Maker
      Infineon
      Package
      Not recorded
      Pins
      Not recorded
      Source
      From the manufacturer's datasheet

      Is it dead?

      Diode range, from the protected line to ground, part lifted if you can.

      Working, it reads

      A one-way part reads about 0.6 to 0.8 V forward and open in reverse. A two-way part reads open both ways. Arrays with several lines read as the datasheet's diagram draws them.

      Dead, it reads

      • From the line to ground, the same reading both ways, near 0 V with a continuous beep: shorted.
      • A reading both ways on a one-way part: leaky.
      • A one-way part open both ways: failed open.
      On the board:
      On the board, a line reading shorted to ground can be this part or anything else on that line. Lift it: if the short goes with it, it has failed.
      Compare:
      The same part on the next line or connector pin is the healthy reading to compare with.
      Watch for:
      A two-way part reads open both ways when it is good, exactly like one that has failed open. The meter cannot tell them apart; an identical part on the next line can.

      A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

14 more parts have codes that begin with AA

Codes that begin with AA

For a marking with its end worn or burnt off. Each one shows its full printed code.

  • AOZ1380DI-01printed AA00Load switch, Alpha & Omega Semiconductor

    Printed AA00. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Load switch
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    USB Type-C protection switch
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage, board powered, black probe on ground.

    Working, it reads

    Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

    Dead, it reads

    • Output at the input voltage while switched off: the pass element has shorted.
    • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
    On the board:
    An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
    Compare:
    If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
    Watch for:
    The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • AOZ1390DI-01printed AA01Load switch, Alpha & Omega Semiconductor

    Printed AA01. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Load switch
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    USB Type-C protection switch
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage, board powered, black probe on ground.

    Working, it reads

    Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

    Dead, it reads

    • Output at the input voltage while switched off: the pass element has shorted.
    • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
    On the board:
    An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
    Compare:
    If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
    Watch for:
    The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • AOZ6605PIprinted AA00DC-DC converter, Alpha & Omega Semiconductor

    Printed AA00. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    DC-DC converter
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    Synchronous buck regulator
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage with the board powered; ohms from each pin to ground with it off.

    Working, it reads

    Supply pin at its voltage and the output doing what the datasheet says. Readings between pins depend on the part.

    Dead, it reads

    • A pin near 0 Ω to ground or to the supply pin where an identical part does not read that: failed short.
    • Supply present, output stuck: failed, or its load has.
    On the board:
    A pin shorted to ground on the board can be anything on that net. Lift the pin to be sure.
    Compare:
    The surest reference is the same IC on a working board, measured pin by pin.
    Watch for:
    Its protection diodes can read like junctions between pins, even like a transistor. That proves nothing either way.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • AOZ6605PI-1printed AA01DC-DC converter, Alpha & Omega Semiconductor

    Printed AA01. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    DC-DC converter
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    Synchronous buck regulator
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage with the board powered; ohms from each pin to ground with it off.

    Working, it reads

    Supply pin at its voltage and the output doing what the datasheet says. Readings between pins depend on the part.

    Dead, it reads

    • A pin near 0 Ω to ground or to the supply pin where an identical part does not read that: failed short.
    • Supply present, output stuck: failed, or its load has.
    On the board:
    A pin shorted to ground on the board can be anything on that net. Lift the pin to be sure.
    Compare:
    The surest reference is the same IC on a working board, measured pin by pin.
    Watch for:
    Its protection diodes can read like junctions between pins, even like a transistor. That proves nothing either way.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • AOZ13058DIprinted AA00Load switch, Alpha & Omega Semiconductor

    Printed AA00. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Load switch
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    USB Type-C protection switch
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage, board powered, black probe on ground.

    Working, it reads

    Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

    Dead, it reads

    • Output at the input voltage while switched off: the pass element has shorted.
    • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
    On the board:
    An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
    Compare:
    If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
    Watch for:
    The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • AOZ13058DI-01printed AA01Load switch, Alpha & Omega Semiconductor

    Printed AA01. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Load switch
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    USB Type-C protection switch
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage, board powered, black probe on ground.

    Working, it reads

    Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

    Dead, it reads

    • Output at the input voltage while switched off: the pass element has shorted.
    • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
    On the board:
    An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
    Compare:
    If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
    Watch for:
    The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • AOZ13058DI-02printed AA02Load switch, Alpha & Omega Semiconductor

    Printed AA02. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Load switch
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    USB Type-C protection switch
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage, board powered, black probe on ground.

    Working, it reads

    Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

    Dead, it reads

    • Output at the input voltage while switched off: the pass element has shorted.
    • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
    On the board:
    An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
    Compare:
    If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
    Watch for:
    The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • AOZ13058DI-03printed AA03Load switch, Alpha & Omega Semiconductor

    Printed AA03. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Load switch
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    USB Type-C protection switch
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage, board powered, black probe on ground.

    Working, it reads

    Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

    Dead, it reads

    • Output at the input voltage while switched off: the pass element has shorted.
    • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
    On the board:
    An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
    Compare:
    If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
    Watch for:
    The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • AOZ13289DI-01printed AA01Load switch, Alpha & Omega Semiconductor

    Printed AA01. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Load switch
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    USB Type-C protection switch
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage, board powered, black probe on ground.

    Working, it reads

    Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

    Dead, it reads

    • Output at the input voltage while switched off: the pass element has shorted.
    • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
    On the board:
    An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
    Compare:
    If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
    Watch for:
    The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • AOZ13929DI-01printed AA01Load switch, Alpha & Omega Semiconductor

    Printed AA01. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Load switch
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    USB Type-C protection switch
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage, board powered, black probe on ground.

    Working, it reads

    Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

    Dead, it reads

    • Output at the input voltage while switched off: the pass element has shorted.
    • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
    On the board:
    An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
    Compare:
    If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
    Watch for:
    The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • AOZ15953DIprinted AA00Load switch, Alpha & Omega Semiconductor

    Printed AA00. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Load switch
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    USB Type-C protection switch
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage, board powered, black probe on ground.

    Working, it reads

    Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

    Dead, it reads

    • Output at the input voltage while switched off: the pass element has shorted.
    • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
    On the board:
    An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
    Compare:
    If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
    Watch for:
    The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • AOZ15953DI-01printed AA01Load switch, Alpha & Omega Semiconductor

    Printed AA01. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Load switch
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    USB Type-C protection switch
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage, board powered, black probe on ground.

    Working, it reads

    Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

    Dead, it reads

    • Output at the input voltage while switched off: the pass element has shorted.
    • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
    On the board:
    An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
    Compare:
    If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
    Watch for:
    The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • AOZ15953DI-02printed AA02Load switch, Alpha & Omega Semiconductor

    Printed AA02. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Load switch
    Maker
    Alpha & Omega Semiconductor
    Package
    Not recorded
    Pins
    Not recorded
    Details
    USB Type-C protection switch
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage, board powered, black probe on ground.

    Working, it reads

    Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

    Dead, it reads

    • Output at the input voltage while switched off: the pass element has shorted.
    • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
    On the board:
    An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
    Compare:
    If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
    Watch for:
    The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

  • SN74AHC1G00DRLprinted AASLogic gate, 5 pins, Texas Instruments

    Printed AAS. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Logic gate
    Maker
    Texas Instruments
    Package
    Not recorded
    Pins
    5
    Details
    Single 2-Input Positive-NAND Gate
    Source
    From the manufacturer's datasheet

    Is it dead?

    Voltage with the board powered; ohms from each pin to ground with it off.

    Working, it reads

    Supply pin at its voltage and the output doing what the datasheet says. Readings between pins depend on the part.

    Dead, it reads

    • A pin near 0 Ω to ground or to the supply pin where an identical part does not read that: failed short.
    • Supply present, output stuck: failed, or its load has.
    On the board:
    A pin shorted to ground on the board can be anything on that net. Lift the pin to be sure.
    Compare:
    The surest reference is the same IC on a working board, measured pin by pin.
    Watch for:
    Its protection diodes can read like junctions between pins, even like a transistor. That proves nothing either way.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

One code, several parts

Marking codes are not unique. In the standard code book, 6H on a SOT-23 is an NPN transistor, a varicap, an N-channel JFET, two digital transistors, a 3.6 V voltage detector: six parts from five makers. So a search shows the parts we hold under that code and under codes easily misread as it, with only the columns that tell them apart.

6Hon a SOT-23, in the code book
  • NPN transistor
  • Varicap
  • N-channel JFET
  • Digital transistor ×2
  • 3.6 V voltage detector

When more than one is left

Tap Help me choose. Up to 4 quick answers: whether the part has failed, then what separates the parts left. Those get ranked with the reasoning and a test that settles it. That uses one identification: 2 a month are free without an account, and 3 with a free account.

When you cannot read it

Tap the camera in the field. We read the characters, keep the ones we are unsure of, and search every reading. A photo too soft to read is turned back on your phone first; if it is the only one you can get, you can still send it.