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SMD code search: identify a part by its marking

3 parts are printed 3OQ. 61 printed with a similar-looking code.

3 parts are printed 3OQ

Not sure which one you have?

Answer up to 4 quick questions and these 3 parts are ranked, with a meter test that settles it. It works on a dead part too.

Voltage supervisor, all ABLIC. What differs:

  • S-19100C28H-M5T2USOT-23-55 pinsSOT-23-55 pins
    What it is
    Voltage supervisor
    Maker
    ABLIC
    Package
    SOT-23-5
    Pins
    5
    Source
    Manufacturer 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.

    Datasheetfor S-19100C28H-M5T2U, opens in a new tab
  • S-19100C28H-N4T2USOT-3434 pinsSOT-3434 pins
    What it is
    Voltage supervisor
    Maker
    ABLIC
    Package
    SOT-343
    Pins
    4
    Source
    Manufacturer 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.

    Datasheetfor S-19100C28H-N4T2U, opens in a new tab
  • 1 more part has no package on record
    • S-19100C28H-I4T1UNot recordedNot recorded
      What it is
      Voltage supervisor
      Maker
      ABLIC
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Manufacturer 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.

      Datasheetfor S-19100C28H-I4T1U, opens in a new tab
61 more parts are printed with a code easy to misread as 3OQ

Printed with a code easy to misread

One character differs, and it is one that is easy to confuse under a lamp. The odd one out is marked on each.

  • 3.0SMC300printed 300SMCTVS diode, 2 pins, YFWTVS diodeSMC2 pinsYFW

    Printed 300 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    TVS diode
    Maker
    YFW
    Package
    SMC
    Pins
    2
    Source
    Manufacturer 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
    , 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.

    Datasheetfor 3.0SMC300, opens in a new tab
  • CN300printed 300SOT-23-6Comparator, 6 pins, ConsonanceComparatorSOT-23-66 pinsConsonance

    Printed 300 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Comparator
    Maker
    Consonance
    Package
    SOT-23-6
    Pins
    6
    Source
    Manufacturer 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.

    Datasheetfor CN300, opens in a new tab
  • S-19100C15H-M5T2Uprinted 3ODSOT-23-5Voltage supervisor, 5 pins, ABLICVoltage supervisorSOT-23-55 pinsABLIC

    Printed 3OD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Voltage supervisor
    Maker
    ABLIC
    Package
    SOT-23-5
    Pins
    5
    Source
    Manufacturer 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.

    Datasheetfor S-19100C15H-M5T2U, opens in a new tab
  • S-19100C15H-N4T2Uprinted 3ODSOT-343Voltage supervisor, 4 pins, ABLICVoltage supervisorSOT-3434 pinsABLIC

    Printed 3OD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Voltage supervisor
    Maker
    ABLIC
    Package
    SOT-343
    Pins
    4
    Source
    Manufacturer 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.

    Datasheetfor S-19100C15H-N4T2U, opens in a new tab
  • S-19100C26H-M5T2Uprinted 3OOSOT-23-5Voltage supervisor, 5 pins, ABLICVoltage supervisorSOT-23-55 pinsABLIC

    Printed 3OO on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Voltage supervisor
    Maker
    ABLIC
    Package
    SOT-23-5
    Pins
    5
    Source
    Manufacturer 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.

    Datasheetfor S-19100C26H-M5T2U, opens in a new tab
  • S-19100C26H-N4T2Uprinted 3OOSOT-343Voltage supervisor, 4 pins, ABLICVoltage supervisorSOT-3434 pinsABLIC

    Printed 3OO on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Voltage supervisor
    Maker
    ABLIC
    Package
    SOT-343
    Pins
    4
    Source
    Manufacturer 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.

    Datasheetfor S-19100C26H-N4T2U, opens in a new tab
  • TU1ZA300printed 300SMAZener diode, 2 pins, Galaxy MicroelectronicsZener diodeSMA2 pinsGalaxy Microelectronics

    Printed 300 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    Galaxy Microelectronics
    Package
    SMA
    Pins
    2
    Details
    300V, 5%, Surface Mount Zener Diodes
    Source
    Manufacturer 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
    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.

    Datasheetfor TU1ZA300, opens in a new tab
  • U1ZA300printed 300SMAZener diode, 2 pins, Galaxy MicroelectronicsZener diodeSMA2 pinsGalaxy Microelectronics

    Printed 300 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    Galaxy Microelectronics
    Package
    SMA
    Pins
    2
    Details
    300V, 5%, Surface Mount Zener Diodes
    Source
    Manufacturer 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
    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.

    Datasheetfor U1ZA300, opens in a new tab
  • 3SK143-Oprinted 3DOSOT-143N-channel MOSFET, 4 pins, PanasonicN-channel MOSFETSOT-1434 pinsPanasonic

    Printed 3DO on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    N-channel MOSFET
    Maker
    Panasonic
    Package
    SOT-143
    Pins
    4
    Details
    MOSFET n-type: Dual gate, UHF, LN, 15V, +30mA, 200mW, Idss=0.2..1.5mA
    Source
    Published code list

    Is it dead?

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

    Working, it reads

    Red probe on the source, black on the drain: about 0.4 to 0.9 V, the body diode. Open the other way. The gate reads open to both other pins, both ways.

    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. Often all three pins end up shorted together.
    • No body diode at all: failed open.
    On the board
    the gate usually has a resistor to the source, so gate to source reads that resistor, which is not a fault. A drain short can be the load. 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.

  • 3SK143-Qprinted 3DQSOT-143N-channel MOSFET, 4 pins, PanasonicN-channel MOSFETSOT-1434 pinsPanasonic

    Printed 3DQ on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    N-channel MOSFET
    Maker
    Panasonic
    Package
    SOT-143
    Pins
    4
    Details
    MOSFET n-type: Dual gate, UHF, LN, 15V, +30mA, 200mW, Idss=3..13mA
    Source
    Published code list

    Is it dead?

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

    Working, it reads

    Red probe on the source, black on the drain: about 0.4 to 0.9 V, the body diode. Open the other way. The gate reads open to both other pins, both ways.

    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. Often all three pins end up shorted together.
    • No body diode at all: failed open.
    On the board
    the gate usually has a resistor to the source, so gate to source reads that resistor, which is not a fault. A drain short can be the load. 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.

  • AAT60030D-S2printed 30DSOT-23Voltage supervisor, 3 pins, Advanced Analog TechnologyVoltage supervisorSOT-233 pinsAdvanced Analog Technology

    Printed 30D on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Voltage supervisor
    Maker
    Advanced Analog Technology
    Package
    SOT-23
    Pins
    3
    Details
    Voltage detector IC: 3.0V±1%, -Reset PPO
    Source
    Published code list

    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.

  • AAT60030D-S5printed 30DSOT-23-5Voltage supervisor, 5 pins, Advanced Analog TechnologyVoltage supervisorSOT-23-55 pinsAdvanced Analog Technology

    Printed 30D on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Voltage supervisor
    Maker
    Advanced Analog Technology
    Package
    SOT-23-5
    Pins
    5
    Details
    Voltage detector IC: 3.0V±1%, -Reset PPO
    Source
    Published code list

    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.

  • AAT60030D-S15printed 30DSOT-143Voltage supervisor, 4 pins, Advanced Analog TechnologyVoltage supervisorSOT-1434 pinsAdvanced Analog Technology

    Printed 30D on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Voltage supervisor
    Maker
    Advanced Analog Technology
    Package
    SOT-143
    Pins
    4
    Details
    Voltage detector IC: 3.0V±1%, -Reset PPO
    Source
    Published code list

    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.

  • AAT60030D-S16printed 30DSOT-89Voltage supervisor, 3 pins, Advanced Analog TechnologyVoltage supervisorSOT-893 pinsAdvanced Analog Technology

    Printed 30D on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Voltage supervisor
    Maker
    Advanced Analog Technology
    Package
    SOT-89
    Pins
    3
    Details
    Voltage detector IC: 3.0V±1%, -Reset PPO
    Source
    Published code list

    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.

  • AP6233A-33NLNGAprinted 3QDSOT-23-5LDO regulator, 5 pins, Anwell SemiconductorLDO regulatorSOT-23-55 pinsAnwell Semiconductor

    Printed 3QD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Anwell Semiconductor
    Package
    SOT-23-5
    Pins
    5
    Details
    Linear voltage regulator IC: LDO, 3.3V±2%, 300mA, -CE, H-free
    Source
    Published code list

    Is it dead?

    Voltage, board powered, black probe on ground. Then ohms with the power off.

    Working, it reads

    Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

    Dead, it reads

    • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
    • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
    • Power off, input to output near 0 Ω: shorted.
    On the board:
    An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
    Compare:
    The same regulator on another rail or another board shows the right voltages and the right resistances.
    Watch for:
    Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

  • AP6233A-33NLNGA1printed 3QDSOT-23-5LDO regulator, 5 pins, Anwell SemiconductorLDO regulatorSOT-23-55 pinsAnwell Semiconductor

    Printed 3QD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Anwell Semiconductor
    Package
    SOT-23-5
    Pins
    5
    Details
    Linear voltage regulator IC: LDO, 3.3V±1%, 300mA, -CE, H-free
    Source
    Published code list

    Is it dead?

    Voltage, board powered, black probe on ground. Then ohms with the power off.

    Working, it reads

    Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

    Dead, it reads

    • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
    • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
    • Power off, input to output near 0 Ω: shorted.
    On the board:
    An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
    Compare:
    The same regulator on another rail or another board shows the right voltages and the right resistances.
    Watch for:
    Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

  • AP6233A-33NLNGPprinted 3QDSOT-353LDO regulator, 5 pins, Anwell SemiconductorLDO regulatorSOT-3535 pinsAnwell Semiconductor

    Printed 3QD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Anwell Semiconductor
    Package
    SOT-353
    Pins
    5
    Details
    Linear voltage regulator IC: LDO, 3.3V±2%, 300mA, -CE, H-free
    Source
    Published code list

    Is it dead?

    Voltage, board powered, black probe on ground. Then ohms with the power off.

    Working, it reads

    Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

    Dead, it reads

    • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
    • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
    • Power off, input to output near 0 Ω: shorted.
    On the board:
    An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
    Compare:
    The same regulator on another rail or another board shows the right voltages and the right resistances.
    Watch for:
    Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

  • AP6233A-33NLNGP1printed 3QDSOT-353LDO regulator, 5 pins, Anwell SemiconductorLDO regulatorSOT-3535 pinsAnwell Semiconductor

    Printed 3QD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Anwell Semiconductor
    Package
    SOT-353
    Pins
    5
    Details
    Linear voltage regulator IC: LDO, 3.3V±1%, 300mA, -CE, H-free
    Source
    Published code list

    Is it dead?

    Voltage, board powered, black probe on ground. Then ohms with the power off.

    Working, it reads

    Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

    Dead, it reads

    • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
    • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
    • Power off, input to output near 0 Ω: shorted.
    On the board:
    An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
    Compare:
    The same regulator on another rail or another board shows the right voltages and the right resistances.
    Watch for:
    Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

  • AP6233A-33NLNPAprinted 3QDSOT-23-5LDO regulator, 5 pins, Anwell SemiconductorLDO regulatorSOT-23-55 pinsAnwell Semiconductor

    Printed 3QD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Anwell Semiconductor
    Package
    SOT-23-5
    Pins
    5
    Details
    Linear voltage regulator IC: LDO, 3.3V±2%, 300mA, -CE
    Source
    Published code list

    Is it dead?

    Voltage, board powered, black probe on ground. Then ohms with the power off.

    Working, it reads

    Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

    Dead, it reads

    • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
    • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
    • Power off, input to output near 0 Ω: shorted.
    On the board:
    An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
    Compare:
    The same regulator on another rail or another board shows the right voltages and the right resistances.
    Watch for:
    Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

  • AP6233A-33NLNPA1printed 3QDSOT-23-5LDO regulator, 5 pins, Anwell SemiconductorLDO regulatorSOT-23-55 pinsAnwell Semiconductor

    Printed 3QD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Anwell Semiconductor
    Package
    SOT-23-5
    Pins
    5
    Details
    Linear voltage regulator IC: LDO, 3.3V±1%, 300mA, -CE
    Source
    Published code list

    Is it dead?

    Voltage, board powered, black probe on ground. Then ohms with the power off.

    Working, it reads

    Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

    Dead, it reads

    • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
    • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
    • Power off, input to output near 0 Ω: shorted.
    On the board:
    An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
    Compare:
    The same regulator on another rail or another board shows the right voltages and the right resistances.
    Watch for:
    Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

  • AP6233A-33NLNPPprinted 3QDSOT-353LDO regulator, 5 pins, Anwell SemiconductorLDO regulatorSOT-3535 pinsAnwell Semiconductor

    Printed 3QD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Anwell Semiconductor
    Package
    SOT-353
    Pins
    5
    Details
    Linear voltage regulator IC: LDO, 3.3V±2%, 300mA, -CE
    Source
    Published code list

    Is it dead?

    Voltage, board powered, black probe on ground. Then ohms with the power off.

    Working, it reads

    Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

    Dead, it reads

    • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
    • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
    • Power off, input to output near 0 Ω: shorted.
    On the board:
    An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
    Compare:
    The same regulator on another rail or another board shows the right voltages and the right resistances.
    Watch for:
    Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

  • AP6233A-33NLNPP1printed 3QDSOT-353LDO regulator, 5 pins, Anwell SemiconductorLDO regulatorSOT-3535 pinsAnwell Semiconductor

    Printed 3QD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Anwell Semiconductor
    Package
    SOT-353
    Pins
    5
    Details
    Linear voltage regulator IC: LDO, 3.3V±1%, 300mA, -CE
    Source
    Published code list

    Is it dead?

    Voltage, board powered, black probe on ground. Then ohms with the power off.

    Working, it reads

    Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

    Dead, it reads

    • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
    • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
    • Power off, input to output near 0 Ω: shorted.
    On the board:
    An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
    Compare:
    The same regulator on another rail or another board shows the right voltages and the right resistances.
    Watch for:
    Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

  • GLZ30Dprinted 30DSOD-80Zener diode, 2 pins, PanjitZener diodeSOD-802 pinsPanjit

    Printed 30D on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    Panjit
    Package
    SOD-80
    Pins
    2
    Details
    Zener diode: 29.02..30.51V, Zzt=55 , Izt=5mA, 500mW
    Source
    Published code list

    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
    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.

  • HM624533PRprinted 3D0SOT-89LDO regulator, 3 pins, Huamei SemiconductorLDO regulatorSOT-893 pinsHuamei Semiconductor

    Printed 3D0 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Huamei Semiconductor
    Package
    SOT-89
    Pins
    3
    Details
    Linear voltage regulator IC: LDO, 3.3V±2%, 1A
    Source
    Published code list

    Is it dead?

    Voltage, board powered, black probe on ground. Then ohms with the power off.

    Working, it reads

    Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

    Dead, it reads

    • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
    • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
    • Power off, input to output near 0 Ω: shorted.
    On the board:
    An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
    Compare:
    The same regulator on another rail or another board shows the right voltages and the right resistances.
    Watch for:
    Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

  • P4SMA300printed 300SMATVS diode, 2 pins, EIC SemiconductorTVS diodeSMA2 pinsEIC Semiconductor

    Printed 300 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    TVS diode
    Maker
    EIC Semiconductor
    Package
    SMA
    Pins
    2
    Details
    Transient voltage supressor: Vbr=270..330V, Vrwm=243V, 0.93A, 400W(1ms)
    Source
    Published code list

    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
    , 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.

  • P4SMAFJ30CAprinted 30DSMAFTVS diode, 2 pins, Dongguan You Feng Wei ElectronicsTVS diodeSMAF2 pinsDongguan You Feng Wei Electronics

    Printed 30D on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    TVS diode
    Maker
    Dongguan You Feng Wei Electronics
    Package
    SMAF
    Pins
    2
    Details
    Transient voltage supressor: Vrwm=30V, Vbr=33.3..38.3V, Ipp=8.3A, 400W(1ms), Bidir.
    Source
    Published code list

    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
    , 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.

  • P4SMAJ30CAprinted 30DSMA2 pins, YeashinNot recordedSMA2 pinsYeashin

    Printed 30D on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Not recorded
    Maker
    Yeashin
    Package
    SMA
    Pins
    2
    Details
    TVS: 30V, 8.3A, 400W(1ms), Bidirectional
    Source
    Published code list

    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
    , 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.

  • P4SMAJ300printed 300SMATVS diode, 2 pins, Sunmate SemiconductorTVS diodeSMA2 pinsSunmate Semiconductor

    Printed 300 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    TVS diode
    Maker
    Sunmate Semiconductor
    Package
    SMA
    Pins
    2
    Details
    Transient voltage supressor: Vrwm=300V, Vbr=332..400V, Ipp=0.57A, 400W(1ms)
    Source
    Published code list

    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
    , 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.

  • P4SMFJ30CAprinted 30DSOD-123FTVS diode, 2 pins, YeashinTVS diodeSOD-123F2 pinsYeashin

    Printed 30D on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    TVS diode
    Maker
    Yeashin
    Package
    SOD-123F
    Pins
    2
    Details
    Transient voltage supressor: Vrwm=30V, Ipp=8.3A, 400W (1ms), Bidir.
    Source
    Published code list

    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
    , 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.

  • TC55RP332ECBprinted 3D0SOT-23LDO regulator, 3 pins, MicrochipLDO regulatorSOT-233 pinsMicrochip

    Printed 3D0 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Microchip
    Package
    SOT-23
    Pins
    3
    Details
    Linear voltage regulator IC: LDO, 3.3V±2%, 250mA
    Source
    Published code list

    Is it dead?

    Voltage, board powered, black probe on ground. Then ohms with the power off.

    Working, it reads

    Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

    Dead, it reads

    • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
    • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
    • Power off, input to output near 0 Ω: shorted.
    On the board:
    An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
    Compare:
    The same regulator on another rail or another board shows the right voltages and the right resistances.
    Watch for:
    Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

  • TC55RP332EMBprinted 3D0SOT-89LDO regulator, 3 pins, MicrochipLDO regulatorSOT-893 pinsMicrochip

    Printed 3D0 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Microchip
    Package
    SOT-89
    Pins
    3
    Details
    Linear voltage regulator IC: LDO, 3.3V±2%, 250mA
    Source
    Published code list

    Is it dead?

    Voltage, board powered, black probe on ground. Then ohms with the power off.

    Working, it reads

    Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

    Dead, it reads

    • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
    • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
    • Power off, input to output near 0 Ω: shorted.
    On the board:
    An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
    Compare:
    The same regulator on another rail or another board shows the right voltages and the right resistances.
    Watch for:
    Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

  • TK11330BUprinted 30QSOT-89-55 pins, TokNot recordedSOT-89-55 pinsTok

    Printed 30Q on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Not recorded
    Maker
    Tok
    Package
    SOT-89-5
    Pins
    5
    Details
    VR-IC: LDO, -CE, 3V±2%, 150mA
    Source
    Published code list

    Is it dead?

    Voltage, board powered, black probe on ground. Then ohms with the power off.

    Working, it reads

    Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

    Dead, it reads

    • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
    • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
    • Power off, input to output near 0 Ω: shorted.
    On the board:
    An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
    Compare:
    The same regulator on another rail or another board shows the right voltages and the right resistances.
    Watch for:
    Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

  • TLZ30Dprinted 30DSOD-80Zener diode, 2 pins, Taitron ComponentsZener diodeSOD-802 pinsTaitron Components

    Printed 30D on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    Taitron Components
    Package
    SOD-80
    Pins
    2
    Details
    Zener diode: 29.02..30.51V, Izt=5mA, 500mW
    Source
    Published code list

    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
    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.

  • 14 more parts have no package on record
    • PLZ30Dprinted 30DZener diode, VishayZener diodeNot recordedNot recordedVishay

      Printed 30D on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      Zener diode
      Maker
      Vishay
      Package
      Not recorded
      Pins
      Not recorded
      Details
      30 V Zener diode
      Source
      Manufacturer 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
      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.

      Datasheetfor PLZ30D, opens in a new tab
    • S-19100C15H-I4T1Uprinted 3ODVoltage supervisor, ABLICVoltage supervisorNot recordedNot recordedABLIC

      Printed 3OD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      Voltage supervisor
      Maker
      ABLIC
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Manufacturer 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.

      Datasheetfor S-19100C15H-I4T1U, opens in a new tab
    • S-19100C26H-I4T1Uprinted 3OOVoltage supervisor, ABLICVoltage supervisorNot recordedNot recordedABLIC

      Printed 3OO on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      Voltage supervisor
      Maker
      ABLIC
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Manufacturer 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.

      Datasheetfor S-19100C26H-I4T1U, opens in a new tab
    • AP6233A-33NLNGUprinted 3QDLDO regulator, Anwell SemiconductorLDO regulatorNot recordedNot recordedAnwell Semiconductor

      Printed 3QD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      LDO regulator
      Maker
      Anwell Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Linear voltage regulator IC: LDO, 3.3V±2%, 300mA, -CE, H-free
      Source
      Published code list

      Is it dead?

      Voltage, board powered, black probe on ground. Then ohms with the power off.

      Working, it reads

      Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

      Dead, it reads

      • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
      • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
      • Power off, input to output near 0 Ω: shorted.
      On the board:
      An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
      Compare:
      The same regulator on another rail or another board shows the right voltages and the right resistances.
      Watch for:
      Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

    • AP6233A-33NLNGU1printed 3QDLDO regulator, Anwell SemiconductorLDO regulatorNot recordedNot recordedAnwell Semiconductor

      Printed 3QD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      LDO regulator
      Maker
      Anwell Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Linear voltage regulator IC: LDO, 3.3V±1%, 300mA, -CE, H-free
      Source
      Published code list

      Is it dead?

      Voltage, board powered, black probe on ground. Then ohms with the power off.

      Working, it reads

      Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

      Dead, it reads

      • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
      • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
      • Power off, input to output near 0 Ω: shorted.
      On the board:
      An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
      Compare:
      The same regulator on another rail or another board shows the right voltages and the right resistances.
      Watch for:
      Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

    • AP6233A-33NLNPUprinted 3QDLDO regulator, Anwell SemiconductorLDO regulatorNot recordedNot recordedAnwell Semiconductor

      Printed 3QD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      LDO regulator
      Maker
      Anwell Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Linear voltage regulator IC: LDO, 3.3V±2%, 300mA, -CE
      Source
      Published code list

      Is it dead?

      Voltage, board powered, black probe on ground. Then ohms with the power off.

      Working, it reads

      Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

      Dead, it reads

      • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
      • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
      • Power off, input to output near 0 Ω: shorted.
      On the board:
      An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
      Compare:
      The same regulator on another rail or another board shows the right voltages and the right resistances.
      Watch for:
      Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

    • AP6233A-33NLNPU1printed 3QDLDO regulator, Anwell SemiconductorLDO regulatorNot recordedNot recordedAnwell Semiconductor

      Printed 3QD on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      LDO regulator
      Maker
      Anwell Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Linear voltage regulator IC: LDO, 3.3V±1%, 300mA, -CE
      Source
      Published code list

      Is it dead?

      Voltage, board powered, black probe on ground. Then ohms with the power off.

      Working, it reads

      Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

      Dead, it reads

      • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
      • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
      • Power off, input to output near 0 Ω: shorted.
      On the board:
      An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
      Compare:
      The same regulator on another rail or another board shows the right voltages and the right resistances.
      Watch for:
      Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

    • HZM3.0NBprinted 300Zener diode, RenesasZener diodeNot recordedNot recordedRenesas

      Printed 300 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      Zener diode
      Maker
      Renesas
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Z-diode: 2.8..3.2V, 200mW
      Source
      Published code list

      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
      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.

    • MAZX300printed 300Zener diode, PanasonicZener diodeNot recordedNot recordedPanasonic

      Printed 300 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      Zener diode
      Maker
      Panasonic
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Zener diode: 270..330V, Zzt=5(0.5mA), 1W
      Source
      Published code list

      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
      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.

    • RKZ30DKUprinted 30DZener diode, RenesasZener diodeNot recordedNot recordedRenesas

      Printed 30D on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      Zener diode
      Maker
      Renesas
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Zener diode: 29.02..30.51V, Izt=5mA, Zzt=80, 500mW
      Source
      Published code list

      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
      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.

    • TK11330BMprinted 30QTokNot recordedNot recordedNot recordedTok

      Printed 30Q on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      Not recorded
      Maker
      Tok
      Package
      Not recorded
      Pins
      Not recorded
      Details
      VR-IC: LDO, -CE, 3V±2%, 150mA
      Source
      Published code list

      Is it dead?

      Voltage, board powered, black probe on ground. Then ohms with the power off.

      Working, it reads

      Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

      Dead, it reads

      • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
      • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
      • Power off, input to output near 0 Ω: shorted.
      On the board:
      An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
      Compare:
      The same regulator on another rail or another board shows the right voltages and the right resistances.
      Watch for:
      Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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

    • U1Z300printed 300ToshibaNot recordedNot recordedNot recordedToshiba

      Printed 300 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      Not recorded
      Maker
      Toshiba
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Z-diode: 270..330V, 1W
      Source
      Published code list

      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
      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.

    • U1ZB300printed 300Zener diode, ToshibaZener diodeNot recordedNot recordedToshiba

      Printed 300 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      Zener diode
      Maker
      Toshiba
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Z-diode: 270..330V, 1W
      Source
      Published code list

      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
      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.

    • VRH3001NVprinted 300LDO regulator, AnaSemLDO regulatorNot recordedNot recordedAnaSem

      Printed 300 on the part. Easy to misread as 3OQ. Check that character with a loupe before you order anything.

      What it is
      LDO regulator
      Maker
      AnaSem
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Linear voltage regulator IC: LDO, 3.0V±1%, 250mA, +CE
      Source
      Published code list

      Is it dead?

      Voltage, board powered, black probe on ground. Then ohms with the power off.

      Working, it reads

      Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

      Dead, it reads

      • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
      • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
      • Power off, input to output near 0 Ω: shorted.
      On the board:
      An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
      Compare:
      The same regulator on another rail or another board shows the right voltages and the right resistances.
      Watch for:
      Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

      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 are not listed here. Type more of the code to narrow the list.

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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 on WhatSMD (What SMD) 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.

Get the app

The same search on your phone, and a camera with a light, zoom and tap to focus for a marking you cannot read. Sign in with your email address to use the same account.

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