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SMD code RW in SOT-323

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.

3 parts in SOT-323 are printed RW

Not sure which one you have?

Answer up to 4 quick questions and these 10 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • CHT858BWGPSOT-323PNP transistor, ChenmkoPNP transistorChenmko
    What it is
    PNP transistor
    Maker
    Chenmko
    Package
    SOT-323
    Pins
    3
    Details
    PNP General Purpose Transistor, 30 V, 0.1 A
    Source
    Manufacturer datasheet

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

  • RU1C001UNSOT-323N-channel MOSFET, ROHMN-channel MOSFETROHM
    What it is
    N-channel MOSFET
    Maker
    ROHM
    Package
    SOT-323
    Pins
    3
    Details
    Nch 20V 100mA Small Signal MOSFET
    Source
    Manufacturer datasheet

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

  • CHT858BWPT-QSOT-323PNP transistor, Chenmko EnterprisePNP transistorChenmko Enterprise
    What it is
    PNP transistor
    Maker
    Chenmko Enterprise
    Package
    SOT-323
    Pins
    3
    Details
    PNP transistor: AF, Sw, 30V, 100mA, B=125..250, 200MHz
    Source
    Published code list

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

  • 7 more parts have no package on record. Nothing rules them out, so they stay.
    • LFCN-575D+RF filter, Mini-CircuitsRF filterMini-Circuits
      What it is
      RF filter
      Maker
      Mini-Circuits
      Package
      Not recorded
      Pins
      Not recorded
      Details
      LTCC filter, DC-575 MHz
      Source
      Manufacturer datasheet

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

    • VS18VUA1VWMTVS diode, ROHMTVS diodeROHM
      What it is
      TVS diode
      Maker
      ROHM
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Transient Voltage Suppressor
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: TVS or ESD protection diode.

    • VS18VUA1VWMTFTVS diode, ROHMTVS diodeROHM
      What it is
      TVS diode
      Maker
      ROHM
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Transient Voltage Suppressor
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: TVS or ESD protection diode.

    • BD5360FVEVoltage supervisor, ROHMVoltage supervisorROHM
      What it is
      Voltage supervisor
      Maker
      ROHM
      Package
      Not recorded
      Pins
      Not recorded
      Details
      CMOS-IC: Voltage Detector 6V, Reset Push-pull output
      Source
      Published code list

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

    • BD5360GVoltage supervisor, ROHMVoltage supervisorROHM
      What it is
      Voltage supervisor
      Maker
      ROHM
      Package
      Not recorded
      Pins
      Not recorded
      Details
      CMOS-IC: Voltage Detector 6V, Reset Push-pull output
      Source
      Published code list

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

    • MCP810T-475MicrochipNot recordedMicrochip
      What it is
      Not recorded
      Maker
      Microchip
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Microprocessor Reset Circuit
      Source
      Published code list

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

    • SM4T39SGS-Thomson MicroelectronicsNot recordedSGS-Thomson Microelectronics
      What it is
      Not recorded
      Maker
      SGS-Thomson Microelectronics
      Package
      Not recorded
      Pins
      Not recorded
      Details
      TVS: 39V, 7,4A, 400W(1ms)
      Source
      Published code list

      Is it dead? The meter test is below: TVS or ESD protection diode.

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.

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.

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

Dead, it reads

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

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

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.

TVS or ESD protection diode

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.

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.

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