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SMD code W18

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.

9 parts are printed W18

Not sure which one you have?

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

  • S-LP1488WT1GSOT-323P-channel MOSFET, 3 pins, LRCP-channel MOSFETSOT-3233 pinsLRC
    What it is
    P-channel MOSFET
    Maker
    LRC
    Package
    SOT-323
    Pins
    3
    Details
    MOSFET, P-Channel, VDSS 20 V, VGS 8 V
    Source
    Manufacturer datasheet

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

    Datasheetfor S-LP1488WT1G, opens in a new tab
  • BFP181TWSOT-3434 pins, VishayNot recordedSOT-3434 pinsVishay
    What it is
    Not recorded
    Maker
    Vishay
    Package
    SOT-343
    Pins
    4
    Details
    Si-npn: UHF, 20V, 20mA, 175mW, B=50..200, 8GHz
    Source
    Published code list

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

  • KIC73B18T2SOT-23Voltage supervisor, 3 pins, KECVoltage supervisorSOT-233 pinsKEC
    What it is
    Voltage supervisor
    Maker
    KEC
    Package
    SOT-23
    Pins
    3
    Details
    Voltage detector IC: 1.8V±1%, -Reset PPO, Rdt=50ms
    Source
    Published code list

    Is it dead? The meter test is below: Integrated circuit.

  • PDTC143ZTSOT-23Digital transistor (NPN, resistors built in), 3 pins, NXPDigital transistor (NPN, resistors built in)SOT-233 pinsNXP
    What it is
    Digital transistor (NPN, resistors built in)
    Maker
    NXP
    Package
    SOT-23
    Pins
    3
    Details
    50 V, 100 mA NPN resistor-equipped transistor; R1 = 4.7 kΩ, R2 = 47 kΩ
    Source
    Published code list

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

    Datasheetfor PDTC143ZT, opens in a new tab
  • PDTC144VUSOT-323Digital transistor (NPN, resistors built in), 3 pins, NXPDigital transistor (NPN, resistors built in)SOT-3233 pinsNXP
    What it is
    Digital transistor (NPN, resistors built in)
    Maker
    NXP
    Package
    SOT-323
    Pins
    3
    Details
    50 V, 100 mA NPN resistor-equipped transistor; R1 = 47 kΩ, R2 = 10 kΩ
    Source
    Published code list

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

    Datasheetfor PDTC144VU, opens in a new tab
  • R1155N118BSOT-23-5LDO regulator, 5 pins, RicohLDO regulatorSOT-23-55 pinsRicoh
    What it is
    LDO regulator
    Maker
    Ricoh
    Package
    SOT-23-5
    Pins
    5
    Details
    Linear voltage regulator IC: LDO, 11.8V±2%, 150mA, +CE, Test
    Source
    Published code list

    Is it dead? The meter test is below: Voltage regulator.

  • R1163N181DSOT-23-55 pins, Nisshinbo Micro DevicesNot recordedSOT-23-55 pinsNisshinbo Micro Devices
    What it is
    Not recorded
    Maker
    Nisshinbo Micro Devices
    Package
    SOT-23-5
    Pins
    5
    Details
    VR-IC: LDO, CE, auto-discharge, 1.8V±1.5%, 150mA
    Source
    Published code list

    Is it dead? The meter test is below: Voltage regulator.

  • 2 more parts have no package on record
    • BFP181TRWTfkNot recordedNot recordedNot recordedTfk
      What it is
      Not recorded
      Maker
      Tfk
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Si-npn: UHF, 20V, 20mA, 175mW, B=50..200, 8GHz
      Source
      Published code list

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

    • KIC73B18M2Voltage supervisor, KECVoltage supervisorNot recordedNot recordedKEC
      What it is
      Voltage supervisor
      Maker
      KEC
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Voltage detector IC: 1.8V±1%, -Reset PPO, Rdt=50ms
      Source
      Published code list

      Is it dead? The meter test is below: Integrated circuit.

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.

P-channel MOSFET

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.

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.

Integrated circuit

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.

Digital transistor

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.

Voltage regulator

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.

Printed with a code easy to misread as W18

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

Codes that begin with W18

For a marking with its end worn or burnt off. Each code has a page of its own.

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