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SMD code TBC in TO-92

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.

1 part in TO-92 is printed TBC

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.

  • BC847B / DGTO-92NPN transistor, 3 pins, NXPNPN transistor3 pinsNXP
    What it is
    NPN transistor
    Maker
    NXP
    Package
    TO-92
    Pins
    3
    Source
    Published code list

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

  • 1 more part has no package on record. Nothing rules it out, so it stays.
    • TL431BCDMVoltage reference, onsemiVoltage referenceNot recordedonsemi
      What it is
      Voltage reference
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Programmable Precision References B Series, B Series
      Source
      Manufacturer datasheet

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

      Datasheetfor TL431BCDM, opens in a new tab

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.

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.

Printed with a code easy to misread as TBC

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 TBC

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

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