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SMD code search: identify a part by its marking

2 parts are printed 39.. 104 printed with a similar-looking code.

2 parts are printed 39.

Not sure which one you have?

Answer up to 4 quick questions and these 2 parts are ranked, with a meter test that settles it. It works on a dead part too.

Zener diode, 2 pins, all Taitron Components. What differs:

  • TZD3.9YWSSOD-323SOD-323
    What it is
    Zener diode
    Maker
    Taitron Components
    Package
    SOD-323
    Pins
    2
    Details
    Zener diode: 3.89..4.16V, Izt=5mA, Zzt=130, 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.

  • TZD3.9YWTSOD-523SOD-523
    What it is
    Zener diode
    Maker
    Taitron Components
    Package
    SOD-523
    Pins
    2
    Details
    Zener diode: 3.89..4.16V, Izt=5mA, Zzt=130, 150mW
    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.

104 more parts are printed with a code easy to misread as 39.

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.

  • 1.5SMC39printed 39SMCTVS diode, 2 pins, HottechTVS diodeSMC2 pinsHottech

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    TVS diode
    Maker
    Hottech
    Package
    SMC
    Pins
    2
    Details
    TVS diode, VRWM 31.6 V, unidirectional
    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 1.5SMC39, opens in a new tab
  • 3.0SMC39printed 39SMCTVS diode, 2 pins, YFWTVS diodeSMC2 pinsYFW

    Printed 39 on the part. Easy to misread as 39.. 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 3.0SMC39, opens in a new tab
  • BZX384-A22printed 39SOD-323Zener diode, 2 pins, NexperiaZener diodeSOD-3232 pinsNexperia

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    Nexperia
    Package
    SOD-323
    Pins
    2
    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 BZX384-A22, opens in a new tab
  • CMS3139KQA-HFprinted 39SOT-883P-channel MOSFET, 3 pins, ComchipP-channel MOSFETSOT-8833 pinsComchip

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    P-channel MOSFET
    Maker
    Comchip
    Package
    SOT-883
    Pins
    3
    Details
    -20 V, -0.66 A P-channel MOSFET
    Source
    Manufacturer datasheet

    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 drain, black on the source: 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. 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.

    Datasheetfor CMS3139KQA-HF, opens in a new tab
  • DTA043TEBprinted 39SOT-416Digital transistor (PNP, resistors built in), 3 pins, ROHMDigital transistor (PNP, resistors built in)SOT-4163 pinsROHM

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Digital transistor (PNP, resistors built in)
    Maker
    ROHM
    Package
    SOT-416
    Pins
    3
    Details
    PNP -100mA -50V Digital Transistor (Bias Resistor Built-in Transistor)
    Source
    Manufacturer datasheet

    Is it dead?

    Ohms range, part lifted. The datasheet gives the built-in resistors: R1 in series with the base, R2 from base to emitter.

    Working, it reads

    Base to emitter reads about R1 plus R2 either way round, about 20 kΩ on a 10 k and 10 k part, give or take their wide tolerance. Collector to emitter reads open. A part with no R2 reads a junction behind R1 one way instead.

    Dead, it reads

    • Collector to emitter the same both ways, near 0 Ω with a continuous beep: shorted.
    • From the base, open or far above R1 plus R2: R1 has failed. Static damage shows here most often.
    • Base to emitter near 0 Ω: failed short.
    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:
    The readings depend on the resistor values, so an identical part elsewhere on the board is the surest reference. Measure it the same way.
    Watch for:
    On the diode range a good part with 10 kΩ resistors reads open on every pair, so a good part looks dead there. Use the ohms range.

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

    Datasheetfor DTA043TEB, opens in a new tab
  • DTA043TMprinted 39SOT-723Digital transistor (PNP, resistors built in), 3 pins, ROHMDigital transistor (PNP, resistors built in)SOT-7233 pinsROHM

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Digital transistor (PNP, resistors built in)
    Maker
    ROHM
    Package
    SOT-723
    Pins
    3
    Details
    PNP -100mA -50V Digital Transistor (Bias Resistor Built-in Transistor)
    Source
    Manufacturer datasheet

    Is it dead?

    Ohms range, part lifted. The datasheet gives the built-in resistors: R1 in series with the base, R2 from base to emitter.

    Working, it reads

    Base to emitter reads about R1 plus R2 either way round, about 20 kΩ on a 10 k and 10 k part, give or take their wide tolerance. Collector to emitter reads open. A part with no R2 reads a junction behind R1 one way instead.

    Dead, it reads

    • Collector to emitter the same both ways, near 0 Ω with a continuous beep: shorted.
    • From the base, open or far above R1 plus R2: R1 has failed. Static damage shows here most often.
    • Base to emitter near 0 Ω: failed short.
    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:
    The readings depend on the resistor values, so an identical part elsewhere on the board is the surest reference. Measure it the same way.
    Watch for:
    On the diode range a good part with 10 kΩ resistors reads open on every pair, so a good part looks dead there. Use the ohms range.

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

    Datasheetfor DTA043TM, opens in a new tab
  • DTA043TUBprinted 39SOT-323Digital transistor (PNP, resistors built in), 3 pins, ROHMDigital transistor (PNP, resistors built in)SOT-3233 pinsROHM

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Digital transistor (PNP, resistors built in)
    Maker
    ROHM
    Package
    SOT-323
    Pins
    3
    Details
    PNP -100mA -50V Digital Transistor (Bias Resistor Built-in Transistor)
    Source
    Manufacturer datasheet

    Is it dead?

    Ohms range, part lifted. The datasheet gives the built-in resistors: R1 in series with the base, R2 from base to emitter.

    Working, it reads

    Base to emitter reads about R1 plus R2 either way round, about 20 kΩ on a 10 k and 10 k part, give or take their wide tolerance. Collector to emitter reads open. A part with no R2 reads a junction behind R1 one way instead.

    Dead, it reads

    • Collector to emitter the same both ways, near 0 Ω with a continuous beep: shorted.
    • From the base, open or far above R1 plus R2: R1 has failed. Static damage shows here most often.
    • Base to emitter near 0 Ω: failed short.
    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:
    The readings depend on the resistor values, so an identical part elsewhere on the board is the surest reference. Measure it the same way.
    Watch for:
    On the diode range a good part with 10 kΩ resistors reads open on every pair, so a good part looks dead there. Use the ohms range.

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

    Datasheetfor DTA043TUB, opens in a new tab
  • GALI-39+printed 39SOT-89RF amplifier (MMIC), 3 pins, Mini-CircuitsRF amplifier (MMIC)SOT-893 pinsMini-Circuits

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    RF amplifier (MMIC)
    Maker
    Mini-Circuits
    Package
    SOT-89
    Pins
    3
    Details
    MMIC amplifier, DC-7 GHz
    Source
    Manufacturer datasheet

    Is it dead?

    Voltage, board powered, on the output pin that the bias resistor or choke feeds.

    Working, it reads

    The output pin sits at the device voltage the datasheet gives, a few volts, below the supply.

    Dead, it reads

    • Output pin at 0 V, or near 0 Ω to ground with the power off: shorted inside.
    • Output pin at the full supply voltage: open inside, no current flowing.
    On the board:
    Measured on the board with power on; the bias network is part of the reading.
    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 figures depend on the part and its bias resistor. 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.

    Datasheetfor GALI-39+, opens in a new tab
  • GSFW02066printed 39SOT-883P-channel MOSFET, 3 pins, Good-ArkP-channel MOSFETSOT-8833 pinsGood-Ark

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    P-channel MOSFET
    Maker
    Good-Ark
    Package
    SOT-883
    Pins
    3
    Details
    P-channel MOSFET, 20 V
    Source
    Manufacturer datasheet

    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 drain, black on the source: 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. 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.

    Datasheetfor GSFW02066, opens in a new tab
  • KDZ3.9EVprinted 39SOD-523Zener diode, 2 pins, KECZener diodeSOD-5232 pinsKEC

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    KEC
    Package
    SOD-523
    Pins
    2
    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 KDZ3.9EV, opens in a new tab
  • KDZ3.9Vprinted 39SOD-323Zener diode, 2 pins, KECZener diodeSOD-3232 pinsKEC

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    KEC
    Package
    SOD-323
    Pins
    2
    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 KDZ3.9V, opens in a new tab
  • MM3Z39VCWprinted 39SOD-323Zener diode, 2 pins, Yangjie Electronic TechZener diodeSOD-3232 pinsYangjie Electronic Tech

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    Yangjie Electronic Tech
    Package
    SOD-323
    Pins
    2
    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 MM3Z39VCW, opens in a new tab
  • MM3Z39VCW-P2-HFprinted 39SOD-323Zener diode, 2 pins, ComchipZener diodeSOD-3232 pinsComchip

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    Comchip
    Package
    SOD-323
    Pins
    2
    Details
    39 V 200 mW 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 MM3Z39VCW-P2-HF, opens in a new tab
  • P6SMBF39printed 39SMBFTVS diode, 2 pins, YFWTVS diodeSMBF2 pinsYFW

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    TVS diode
    Maker
    YFW
    Package
    SMBF
    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 P6SMBF39, opens in a new tab
  • PMBFJ109printed 39SOT-23JFET, 3 pins, NXPJFETSOT-233 pinsNXP

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    JFET
    Maker
    NXP
    Package
    SOT-23
    Pins
    3
    Details
    N-channel junction FETs
    Source
    Manufacturer datasheet

    Is it dead?

    Ohms range for drain to source, diode range for the gate, part lifted.

    Working, it reads

    Drain to source conducts both ways at a few hundred ohms, depending on the part, and some meters beep on it. The gate reads one junction to drain and to source, about 0.6 to 0.7 V, and open the other way.

    Dead, it reads

    • The gate the same both ways to drain or source, near 0 V with a continuous beep: gate shorted.
    • Drain to source open: the channel has failed open.
    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:
    Drain to source resistance varies from part to part. An identical part elsewhere on the board shows what is normal.
    Watch for:
    A good channel can beep like a short between drain and source. That is normal; the gate junction says whether it has failed.

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

    Datasheetfor PMBFJ109, opens in a new tab
  • PSA-39+printed 39SOT-363RF amplifier (MMIC), 6 pins, Mini-CircuitsRF amplifier (MMIC)SOT-3636 pinsMini-Circuits

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    RF amplifier (MMIC)
    Maker
    Mini-Circuits
    Package
    SOT-363
    Pins
    6
    Details
    MMIC amplifier, DC-6 GHz
    Source
    Manufacturer datasheet

    Is it dead?

    Voltage, board powered, on the output pin that the bias resistor or choke feeds.

    Working, it reads

    The output pin sits at the device voltage the datasheet gives, a few volts, below the supply.

    Dead, it reads

    • Output pin at 0 V, or near 0 Ω to ground with the power off: shorted inside.
    • Output pin at the full supply voltage: open inside, no current flowing.
    On the board:
    Measured on the board with power on; the bias network is part of the reading.
    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 figures depend on the part and its bias resistor. 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.

    Datasheetfor PSA-39+, opens in a new tab
  • RB068MM200printed 39SOD-123FSchottky diode, 2 pins, ROHMSchottky diodeSOD-123F2 pinsROHM

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Schottky diode
    Maker
    ROHM
    Package
    SOD-123F
    Pins
    2
    Details
    Schottky Barrier Diode
    Source
    Manufacturer datasheet

    Is it dead?

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

    Working, it reads

    About 0.15 to 0.45 V anode to cathode, roughly half a silicon diode, and open the other way.

    Dead, it reads

    • The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
    • A reading the wrong way round as well: leaky.
    • Open both ways: failed open.
    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 large Schottky can read about 0.1 V forward and beep like a short, and leaks a little the wrong way when good, more when warm. It is shorted only if it reads the same both ways. Measure it cold, beside an identical cold one.

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

    Datasheetfor RB068MM200, opens in a new tab
  • RB068MM200TFprinted 39SOD-123FSchottky diode, 2 pins, ROHMSchottky diodeSOD-123F2 pinsROHM

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Schottky diode
    Maker
    ROHM
    Package
    SOD-123F
    Pins
    2
    Details
    Schottky Barrier Diode (AEC-Q101 qualified)
    Source
    Manufacturer datasheet

    Is it dead?

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

    Working, it reads

    About 0.15 to 0.45 V anode to cathode, roughly half a silicon diode, and open the other way.

    Dead, it reads

    • The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
    • A reading the wrong way round as well: leaky.
    • Open both ways: failed open.
    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 large Schottky can read about 0.1 V forward and beep like a short, and leaks a little the wrong way when good, more when warm. It is shorted only if it reads the same both ways. Measure it cold, beside an identical cold one.

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

    Datasheetfor RB068MM200TF, opens in a new tab
  • RB081LAM-20printed 39SOD-128Schottky diode, 2 pins, ROHMSchottky diodeSOD-1282 pinsROHM

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Schottky diode
    Maker
    ROHM
    Package
    SOD-128
    Pins
    2
    Details
    Schottky Barrier Diode
    Source
    Manufacturer datasheet

    Is it dead?

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

    Working, it reads

    About 0.15 to 0.45 V anode to cathode, roughly half a silicon diode, and open the other way.

    Dead, it reads

    • The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
    • A reading the wrong way round as well: leaky.
    • Open both ways: failed open.
    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 large Schottky can read about 0.1 V forward and beep like a short, and leaks a little the wrong way when good, more when warm. It is shorted only if it reads the same both ways. Measure it cold, beside an identical cold one.

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

    Datasheetfor RB081LAM-20, opens in a new tab
  • SMA2EZ39D5printed 39SMAZener diode, 2 pins, HXYZener diodeSMA2 pinsHXY

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    HXY
    Package
    SMA
    Pins
    2
    Details
    Zener diode, 24 V
    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 SMA2EZ39D5, opens in a new tab
  • SML4754printed 39SMAZener diode, 2 pins, VishayZener diodeSMA2 pinsVishay

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    Vishay
    Package
    SMA
    Pins
    2
    Details
    39 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 SML4754, opens in a new tab
  • SWJ3139K-Cprinted 39SOT-883MOSFET, 3 pins, SeCoSMOSFETSOT-8833 pinsSeCoS

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    MOSFET
    Maker
    SeCoS
    Package
    SOT-883
    Pins
    3
    Source
    Manufacturer 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
    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.

    Datasheetfor SWJ3139K-C, opens in a new tab
  • TZD3.9WSprinted 39SOD-323Zener diode, 2 pins, Taitron ComponentsZener diodeSOD-3232 pinsTaitron Components

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    Taitron Components
    Package
    SOD-323
    Pins
    2
    Details
    SMD Zener Diodes (Two Terminals) - 200mW
    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 TZD3.9WS, opens in a new tab
  • TZD3.9WTprinted 39SOD-523Zener diode, 2 pins, Taitron ComponentsZener diodeSOD-5232 pinsTaitron Components

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    Taitron Components
    Package
    SOD-523
    Pins
    2
    Details
    SMD Zener Diodes (Two Terminals) - 150mW
    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 TZD3.9WT, opens in a new tab
  • TZT3.9Wprinted 39SOT-23Zener diode, 3 pins, Taitron ComponentsZener diodeSOT-233 pinsTaitron Components

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Zener diode
    Maker
    Taitron Components
    Package
    SOT-23
    Pins
    3
    Details
    SMD Zener Diodes (Three Terminals) - 200mW
    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 TZT3.9W, opens in a new tab
  • EIA-96:39printed 390603Precision resistor (EIA-96 code), 2 pinsPrecision resistor (EIA-96 code)06032 pinsNot recorded

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Precision resistor (EIA-96 code)
    Maker
    Not recorded
    Package
    0603
    Pins
    2
    Details
    EIA-96 precision chip resistor, code 39 stands for 249 in the E96 table; the printed mark adds a multiplier letter (39A = 249 Ohm, 39B = 2.49 kOhm)
    Source
    Added by hand from a published table

    Is it dead?

    Ohms range, across it, power off.

    Working, it reads

    Its marked value, within tolerance. On the board it reads the same or lower, because everything around it sits in parallel.

    Dead, it reads

    • Open: burnt, cracked, or eaten through by sulphur. The commonest failure.
    • Well above its marked value: drifted high.
    • On the board, clearly higher than its marked value: it has failed, since the board can only pull a reading down.
    On the board:
    A reading lower than marked on the board proves nothing; lift one end. A reading higher than marked is a fault even on the board.
    Compare:
    The same position on another channel usually carries the same value, and so does the matching part on another board.
    Watch for:
    A burnt resistor usually means the part it feeds pulled too much. Find that before fitting a new one, or it burns too. The marking, not the reading, says what to fit.

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

    Datasheetfor EIA-96:39, opens in a new tab
  • 2SA1037MPT-Rprinted 39SOT-723PNP transistor, 3 pins, Chenmko EnterprisePNP transistorSOT-7233 pinsChenmko Enterprise

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    PNP transistor
    Maker
    Chenmko Enterprise
    Package
    SOT-723
    Pins
    3
    Details
    PNP transistor: AF, 60V, 150mA, 200mW, B=180..390, 140MHz
    Source
    Published code list

    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
    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.

  • AP8822N-09GAprinted 39SOT-23Voltage supervisor, 3 pins, Anwell SemiconductorVoltage supervisorSOT-233 pinsAnwell Semiconductor

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Voltage supervisor
    Maker
    Anwell Semiconductor
    Package
    SOT-23
    Pins
    3
    Details
    Voltage detector IC: 0.9V±2%, -Reset ODO, Rdt=200ms, H-free
    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.

  • AP8822N-09GTprinted 39SOT-323Voltage supervisor, 3 pins, Anwell SemiconductorVoltage supervisorSOT-3233 pinsAnwell Semiconductor

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Voltage supervisor
    Maker
    Anwell Semiconductor
    Package
    SOT-323
    Pins
    3
    Details
    Voltage detector IC: 0.9V±2%, -Reset ODO, Rdt=200ms, H-free
    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.

  • AP8822N-09PAprinted 39SOT-23Voltage supervisor, 3 pins, Anwell SemiconductorVoltage supervisorSOT-233 pinsAnwell Semiconductor

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Voltage supervisor
    Maker
    Anwell Semiconductor
    Package
    SOT-23
    Pins
    3
    Details
    Voltage detector IC: 0.9V±2%, -Reset ODO, Rdt=200ms
    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.

  • AP8822N-09PTprinted 39SOT-323Voltage supervisor, 3 pins, Anwell SemiconductorVoltage supervisorSOT-3233 pinsAnwell Semiconductor

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    Voltage supervisor
    Maker
    Anwell Semiconductor
    Package
    SOT-323
    Pins
    3
    Details
    Voltage detector IC: 0.9V±2%, -Reset ODO, Rdt=200ms
    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.

  • BL8063CKETR39printed 39DFNLDO regulator, Shanghai BellingLDO regulatorDFNNot recordedShanghai Belling

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Shanghai Belling
    Package
    DFN
    Pins
    Not recorded
    Details
    Linear voltage regulator IC: LDO, 3.9V±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.

  • BL8563CKETR39printed 39DFNLDO regulator, Shanghai BellingLDO regulatorDFNNot recordedShanghai Belling

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Shanghai Belling
    Package
    DFN
    Pins
    Not recorded
    Details
    Linear voltage regulator IC: LDO, 3.9V±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.

  • BL8563CKFTR39printed 39DFNLDO regulator, Shanghai BellingLDO regulatorDFNNot recordedShanghai Belling

    Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

    What it is
    LDO regulator
    Maker
    Shanghai Belling
    Package
    DFN
    Pins
    Not recorded
    Details
    Linear voltage regulator IC: LDO, 3.9V±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.

  • 14 more parts have no package on record
    • FMOSAE0P66P02K-Hprinted 39MOSFET, Formosa MicrosemiMOSFETNot recordedNot recordedFormosa Microsemi

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      MOSFET
      Maker
      Formosa Microsemi
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Manufacturer 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
      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.

      Datasheetfor FMOSAE0P66P02K-H, opens in a new tab
    • LEE-39+printed 39RF amplifier (MMIC), Mini-CircuitsRF amplifier (MMIC)Not recordedNot recordedMini-Circuits

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      RF amplifier (MMIC)
      Maker
      Mini-Circuits
      Package
      Not recorded
      Pins
      Not recorded
      Details
      MMIC amplifier, DC-8 GHz
      Source
      Manufacturer datasheet

      Is it dead?

      Voltage, board powered, on the output pin that the bias resistor or choke feeds.

      Working, it reads

      The output pin sits at the device voltage the datasheet gives, a few volts, below the supply.

      Dead, it reads

      • Output pin at 0 V, or near 0 Ω to ground with the power off: shorted inside.
      • Output pin at the full supply voltage: open inside, no current flowing.
      On the board:
      Measured on the board with power on; the bias network is part of the reading.
      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 figures depend on the part and its bias resistor. 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.

      Datasheetfor LEE-39+, opens in a new tab
    • SGM2038-0.9XUDY4Gprinted 39LDO regulator, 4 pins, SG MicroLDO regulatorNot recorded4 pinsSG Micro

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      LDO regulator
      Maker
      SG Micro
      Package
      Not recorded
      Pins
      4
      Details
      0.9 V output, 500mA, Low Noise, Very Low Dropout Bias Rail CMOS Voltage Regulator
      Source
      Manufacturer datasheet

      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.

      Datasheetfor SGM2038-0.9XUDY4G, opens in a new tab
    • WS4639FC-12printed 39WillsemiNot recordedNot recordedNot recordedWillsemi

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      Not recorded
      Maker
      Willsemi
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Manufacturer datasheet

      Is it dead?

      Diode range and ohms range, part lifted.

      Working, it reads

      Depends on what it is. The datasheet, or an identical part, says.

      Dead, it reads

      • Between two pins, the same reading both ways, near 0 V with a continuous beep: shorted.
      • Open between every pair of pins: failed open, or a part that reads open when working.
      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.

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

      Datasheetfor WS4639FC-12, opens in a new tab
    • 02DZ3.9Xprinted 39Zener diode, ToshibaZener diodeNot recordedNot recordedToshiba

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      Zener diode
      Maker
      Toshiba
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Zener diode: 3.70..3.97V, Iz=5mA, Zz=130, 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.

    • 02DZ3.9Zprinted 39Zener diode, ToshibaZener diodeNot recordedNot recordedToshiba

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      Zener diode
      Maker
      Toshiba
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Zener diode: 3.87..4.10V, Iz=5mA, Zz=130, 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.

    • 2SA1037M1PT-Rprinted 39PNP transistor, Chenmko EnterprisePNP transistorNot recordedNot recordedChenmko Enterprise

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      PNP transistor
      Maker
      Chenmko Enterprise
      Package
      Not recorded
      Pins
      Not recorded
      Details
      PNP transistor: AF, 60V, 150mA, 200mW, B=180..390, 140MHz
      Source
      Published code list

      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
      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.

    • AP8822N-09GIprinted 39Voltage supervisor, Anwell SemiconductorVoltage supervisorNot recordedNot recordedAnwell Semiconductor

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      Voltage supervisor
      Maker
      Anwell Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Voltage detector IC: 0.9V±2%, -Reset ODO, 200ms Rt delay, H-free
      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.

    • AP8822N-09GSprinted 39Voltage supervisor, Anwell SemiconductorVoltage supervisorNot recordedNot recordedAnwell Semiconductor

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      Voltage supervisor
      Maker
      Anwell Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Voltage detector IC: 0.9V±2%, -Reset ODO, 200ms Rt delay, H-free
      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.

    • AP8822N-09PIprinted 39Voltage supervisor, Anwell SemiconductorVoltage supervisorNot recordedNot recordedAnwell Semiconductor

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      Voltage supervisor
      Maker
      Anwell Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Voltage detector IC: 0.9V±2%, -Reset ODO, 200ms Rt delay
      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.

    • AP8822N-09PSprinted 39Voltage supervisor, Anwell SemiconductorVoltage supervisorNot recordedNot recordedAnwell Semiconductor

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      Voltage supervisor
      Maker
      Anwell Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Voltage detector IC: 0.9V±2%, -Reset ODO, 200ms Rt delay
      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.

    • CDZ55C39printed 39Zener diode, Crownpo TechnologyZener diodeNot recordedNot recordedCrownpo Technology

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      Zener diode
      Maker
      Crownpo Technology
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Zener diode: 37.05..40.95V, Zzt=90, 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.

    • CDZ55C39Sprinted 39Zener diode, Crownpo TechnologyZener diodeNot recordedNot recordedCrownpo Technology

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      Zener diode
      Maker
      Crownpo Technology
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Zener diode: 37.05..40.95V, Zzt=90, 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.

    • CDZ55C39Tprinted 39Zener diode, Crownpo TechnologyZener diodeNot recordedNot recordedCrownpo Technology

      Printed 39 on the part. Easy to misread as 39.. Check that character with a loupe before you order anything.

      What it is
      Zener diode
      Maker
      Crownpo Technology
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Zener diode: 37.05..40.95V, Zzt=90, Izt=5mA, 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.

56 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.

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