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WhatSMDSign in

SMD code B-

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.

141 parts are printed B-

Not sure which one you have?

Answer up to 4 quick questions and these 50 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • BAT54X-CSOD-523Schottky diode, 2 pins, SeCoSSchottky diodeSOD-5232 pinsSeCoS
    What it is
    Schottky diode
    Maker
    SeCoS
    Package
    SOD-523
    Pins
    2
    Source
    Manufacturer datasheet

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

    Datasheetfor BAT54X-C, opens in a new tab
  • BB555-02VSOD-5232 pins, InfineonNot recordedSOD-5232 pinsInfineon
    What it is
    Not recorded
    Maker
    Infineon
    Package
    SOD-523
    Pins
    2
    Source
    Manufacturer datasheet

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

    Datasheetfor BB555-02V, opens in a new tab
  • CH520S-30AGPSOD-523Schottky diode, 2 pins, ChenmkoSchottky diodeSOD-5232 pinsChenmko
    What it is
    Schottky diode
    Maker
    Chenmko
    Package
    SOD-523
    Pins
    2
    Details
    SCHOTTKY BARRIER DIODE, 30 V, 0.2 A
    Source
    Manufacturer datasheet

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

    Datasheetfor CH520S-30AGP, opens in a new tab
  • CH520S-30GPSOD-523Schottky diode, 2 pins, ChenmkoSchottky diodeSOD-5232 pinsChenmko
    What it is
    Schottky diode
    Maker
    Chenmko
    Package
    SOD-523
    Pins
    2
    Details
    SCHOTTKY BARRIER DIODE, 30 V, 0.2 A
    Source
    Manufacturer datasheet

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

    Datasheetfor CH520S-30GP, opens in a new tab
  • CH3904TGPSOT-416NPN transistor, 3 pins, ChenmkoNPN transistorSOT-4163 pinsChenmko
    What it is
    NPN transistor
    Maker
    Chenmko
    Package
    SOT-416
    Pins
    3
    Details
    NPN Switching Transistor, 40 V, 0.2 A
    Source
    Manufacturer datasheet

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

    Datasheetfor CH3904TGP, opens in a new tab
  • CHTN02DTGP-ASOT-416NPN transistor, 3 pins, ChenmkoNPN transistorSOT-4163 pinsChenmko
    What it is
    NPN transistor
    Maker
    Chenmko
    Package
    SOT-416
    Pins
    3
    Details
    NPN Switching Transistor, 40 V, 0.2 A
    Source
    Manufacturer datasheet

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

    Datasheetfor CHTN02DTGP-A, opens in a new tab
  • ESD9D3V3CSOD-923ESD protection diode, 2 pins, LeiditechESD protection diodeSOD-9232 pinsLeiditech
    What it is
    ESD protection diode
    Maker
    Leiditech
    Package
    SOD-923
    Pins
    2
    Details
    ESD protection diode, VRWM 3.3 V, Cj 15 pF
    Source
    Manufacturer datasheet

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

    Datasheetfor ESD9D3V3C, opens in a new tab
  • ESD9X5.0SSOD-923ESD protection diode, 2 pins, onsemiESD protection diodeSOD-9232 pinsonsemi
    What it is
    ESD protection diode
    Maker
    onsemi
    Package
    SOD-923
    Pins
    2
    Details
    ESD Protection Diode Series, Series
    Source
    Manufacturer datasheet

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

    Datasheetfor ESD9X5.0S, opens in a new tab
  • 7 more parts have no package on record

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.

Schottky diode

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.

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.

RF amplifier

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.

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.

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.

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