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SMD code ZC in SOT-23

Marking codes are not standardised, and the same code is reused by unrelated makers for unrelated parts. Below is every part in our tables printed with it, and any printed with a code that is easy to misread as it, from the manufacturers' own marking tables and published code lists.

Not sure which one you have?

Answer up to 4 quick questions and these 48 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • 2N3904SSOT-23NPN transistor, 3 pins, Taitron ComponentsNPN transistor3 pinsTaitron Components
    What it is
    NPN transistor
    Maker
    Taitron Components
    Package
    SOT-23
    Pins
    3
    Details
    Bipolar transistor, 40 V, 0.2 A
    Source
    Manufacturer datasheet

    Is it dead? The meter test is below: NPN transistor.

  • MMBT4124LSOT-23NPN transistor, 3 pins, onsemiNPN transistor3 pinsonsemi
    What it is
    NPN transistor
    Maker
    onsemi
    Package
    SOT-23
    Pins
    3
    Source
    Manufacturer datasheet

    Is it dead? The meter test is below: NPN transistor.

  • 2N3906SSOT-23PNP transistor, 3 pins, KECPNP transistor3 pinsKEC
    What it is
    PNP transistor
    Maker
    KEC
    Package
    SOT-23
    Pins
    3
    Details
    Bipolar transistor, 40 V, 0.2 A
    Source
    An older or alternative marking, from a published code list

    Is it dead? The meter test is below: PNP transistor.

  • 2SK217-CSOT-233 pins, RenesasNot recorded3 pinsRenesas
    What it is
    Not recorded
    Maker
    Renesas
    Package
    SOT-23
    Pins
    3
    Details
    FET n-type: VHF, 30V, 20mA, 150mA, Idss=2.5..5mA, Up<2.5V
    Source
    Published code list

    Is it dead? The meter test is below: MOSFET.

  • BCW60RCSOT-233 pins, VishayNot recorded3 pinsVishay
    What it is
    Not recorded
    Maker
    Vishay
    Package
    SOT-23
    Pins
    3
    Details
    equivalent BC548B
    Source
    Published code list

    Is it dead? The meter test is below: This part.

  • BZX84C2V7SOT-23Zener diode, 3 pins, Diodes IncorporatedZener diode3 pinsDiodes Incorporated
    What it is
    Zener diode
    Maker
    Diodes Incorporated
    Package
    SOT-23
    Pins
    3
    Source
    Published code list

    Is it dead? The meter test is below: Zener diode.

  • FMMT4124SOT-233 pinsNot recorded3 pinsNot recorded
    What it is
    Not recorded
    Maker
    Not recorded
    Package
    SOT-23
    Pins
    3
    Details
    2N4124
    Source
    Published code list

    Is it dead? The meter test is below: This part.

  • KST4124SOT-233 pins, Fairchild SemiconductorNot recorded3 pinsFairchild Semiconductor
    What it is
    Not recorded
    Maker
    Fairchild Semiconductor
    Package
    SOT-23
    Pins
    3
    Details
    Si-npn: Sw, 30V, 200mA, 330mW, B=120..360, >300MHz
    Source
    Published code list

    Is it dead? The meter test is below: This part.

  • MMBT3904SOT-23NPN transistor, 3 pinsNPN transistor3 pinsNot recorded
    What it is
    NPN transistor
    Maker
    Not recorded
    Package
    SOT-23
    Pins
    3
    Details
    NPN bipolar transistor
    Source
    Published code list

    Is it dead? The meter test is below: NPN transistor.

  • MMBT4124SOT-23NPN transistor, 3 pins, Fairchild SemiconductorNPN transistor3 pinsFairchild Semiconductor
    What it is
    NPN transistor
    Maker
    Fairchild Semiconductor
    Package
    SOT-23
    Pins
    3
    Details
    Bipolar transistor, 40 V, 0.2 A
    Source
    Published code list

    Is it dead? The meter test is below: NPN transistor.

  • MMBT4124LT1SOT-233 pins, onsemiNot recorded3 pinsonsemi
    What it is
    Not recorded
    Maker
    onsemi
    Package
    SOT-23
    Pins
    3
    Details
    equivalent 2N4124
    Source
    Published code list

    Is it dead? The meter test is below: This part.

  • YTS4124SOT-23NPN transistor, 3 pins, ToshibaNPN transistor3 pinsToshiba
    What it is
    NPN transistor
    Maker
    Toshiba
    Package
    SOT-23
    Pins
    3
    Details
    Si-npn: Sw, 30V, 200mA, 330mW, B=120..360, >300MHz
    Source
    Published code list

    Is it dead? The meter test is below: NPN transistor.

  • 3 more parts have no package on record. Nothing rules them out, so they stay.

Is it dead? One meter test per kind

Parts of the same kind are tested the same way, so each test is here once. Each part above points to its own.

NPN transistor

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

Working, it reads

Red 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.

PNP transistor

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.

MOSFET

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.

This part

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.

Zener diode

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.

Printed with a code easy to misread as ZC

One character differs, and it is one that is easy to confuse under a lamp. Each code has a page of its own.

Codes not listed here are printed on 170 more parts.

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