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SMD code TKB 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.

2 parts in SOT-23 are printed TKB

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.

all SOT-23, 3 pins. What differs:

  • BSH205G2SOT-23NXPNot recordedNXP
    What it is
    Not recorded
    Maker
    NXP
    Package
    SOT-23
    Pins
    3
    Source
    Published code list

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

  • CHDTC143TKPTSOT-23Digital transistor (NPN, resistors built in), Chenmko EnterpriseDigital transistor (NPN, resistors built in)Chenmko Enterprise
    What it is
    Digital transistor (NPN, resistors built in)
    Maker
    Chenmko Enterprise
    Package
    SOT-23
    Pins
    3
    Details
    NPN transistor: Sw, 50V, 100mA, 250MHz, R1=4.7k
    Source
    Published code list

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

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.

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.

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.

Printed with a code easy to misread as TKB

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

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