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SMD code GD1

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.

3 parts are printed GD1

Not sure which one you have?

Answer up to 4 quick questions and these 3 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • FP6187-25S5SOT-23-5LDO regulator, 5 pins, FitipowerLDO regulatorSOT-23-55 pinsFitipower
    What it is
    LDO regulator
    Maker
    Fitipower
    Package
    SOT-23-5
    Pins
    5
    Details
    300mA, Low Noise High PSRR LDO Regulator
    Source
    Manufacturer datasheet

    Is it dead? The meter test is below: Voltage regulator.

    Datasheetfor FP6187-25S5, opens in a new tab
  • AZ810NLTRSOT-233 pins, Diodes IncorporatedNot recordedSOT-233 pinsDiodes Incorporated
    What it is
    Not recorded
    Maker
    Diodes Incorporated
    Package
    SOT-23
    Pins
    3
    Details
    uP reset cct 4.63V threshold, active hi
    Source
    Published code list

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

  • BCW31SOT-23NPN transistor, 3 pins, ROHMNPN transistorSOT-233 pinsROHM
    What it is
    NPN transistor
    Maker
    ROHM
    Package
    SOT-23
    Pins
    3
    Details
    Bipolar transistor, 40 V, 0.2 A
    Source
    Published code list

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

    Datasheetfor BCW31, 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.

Voltage regulator

Voltage, board powered, black probe on ground. Then ohms with the power off.

Working, it reads

Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.

Dead, it reads

  • Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
  • Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
  • Power off, input to output near 0 Ω: shorted.
On the board:
An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
Compare:
The same regulator on another rail or another board shows the right voltages and the right resistances.
Watch for:
Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.

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.

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.

Printed with a code easy to misread as GD1

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

Codes not listed here are printed on 6 more parts.

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