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SMD code GUB

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.

4 parts are printed GUB

Not sure which one you have?

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

  • CHDTC124GUGPSOT-323Digital transistor (NPN, resistors built in), 3 pins, ChenmkoDigital transistor (NPN, resistors built in)SOT-3233 pinsChenmko
    What it is
    Digital transistor (NPN, resistors built in)
    Maker
    Chenmko
    Package
    SOT-323
    Pins
    3
    Details
    NPN Digital Silicon Transistor, 50 V, 100 mA
    Source
    Manufacturer datasheet

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

    Datasheetfor CHDTC124GUGP, opens in a new tab
  • CHDTC124GUPTSOT-323Digital transistor (NPN, resistors built in), 3 pins, Chenmko EnterpriseDigital transistor (NPN, resistors built in)SOT-3233 pinsChenmko Enterprise
    What it is
    Digital transistor (NPN, resistors built in)
    Maker
    Chenmko Enterprise
    Package
    SOT-323
    Pins
    3
    Details
    NPN transistor: Sw, 50V, 100mA, 250MHz, R2=22k
    Source
    Published code list

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

  • SMCJ70ASMCTVS diode, 2 pins, SGS-Thomson MicroelectronicsTVS diodeSMC2 pinsSGS-Thomson Microelectronics
    What it is
    TVS diode
    Maker
    SGS-Thomson Microelectronics
    Package
    SMC
    Pins
    2
    Source
    Published code list

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

    Datasheetfor SMCJ70A, opens in a new tab
  • 1 more part has no package on record
    • SMCJ70A-TR2 pins, STMicroelectronicsNot recordedNot recorded2 pinsSTMicroelectronics
      What it is
      Not recorded
      Maker
      STMicroelectronics
      Package
      Not recorded
      Pins
      2
      Source
      Published code list

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

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.

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.

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.

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.

Printed with a code easy to misread as GUB

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 GUB

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

Codes not listed here are printed on 49 more parts.

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