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SMD code C1M 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.

1 part in SOT-23 is printed C1M

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.

  • CMPTA13SOT-23Darlington transistor, Central SemiconductorDarlington transistorCentral Semiconductor
    What it is
    Darlington transistor
    Maker
    Central Semiconductor
    Package
    SOT-23
    Pins
    3
    Details
    Si-npn-Darl: GP, 30V, 500mA, 350mW, B>5000, >125MHz
    Source
    Published code list

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

  • 1 more part has no package on record. Nothing rules it out, so it stays.
    • uPC2723TBRF amplifier (MMIC), NEC ElectronicsRF amplifier (MMIC)NEC Electronics
      What it is
      RF amplifier (MMIC)
      Maker
      NEC Electronics
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Monolithic microwave IC: Differential AGC amplifier, 1.1GHz, Ucc=5V
      Source
      Published code list

      Is it dead? The meter test is below: RF amplifier.

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.

Darlington transistor

Diode range, part lifted or its base leg off the pad.

Working, it reads

From the base, one probe colour reads about 0.6 to 0.75 V to the collector and about 1.1 to 1.4 V to the emitter, two junctions in series, and open the other way round. Collector to emitter reads open. Built-in resistors can change these readings.

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.

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.

Printed with a code easy to misread as C1M

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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