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SMD code PAB

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.

7 parts are printed PAB

Not sure which one you have?

Answer up to 4 quick questions and these 7 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • BAW101SOT-143Diode, 4 pins, NXPDiodeSOT-1434 pinsNXP
    What it is
    Diode
    Maker
    NXP
    Package
    SOT-143
    Pins
    4
    Source
    Published code list

    Is it dead? The meter test is below: Silicon diode.

    Datasheetfor BAW101, opens in a new tab
  • BC818-25SOT-23Transistor, 3 pins, AUK SemiconductorTransistorSOT-233 pinsAUK Semiconductor
    What it is
    Transistor
    Maker
    AUK Semiconductor
    Package
    SOT-23
    Pins
    3
    Source
    Published code list

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

    Datasheetfor BC818-25, opens in a new tab
  • BF1210SOT-363N-channel MOSFET, 6 pins, NXPN-channel MOSFETSOT-3636 pinsNXP
    What it is
    N-channel MOSFET
    Maker
    NXP
    Package
    SOT-363
    Pins
    6
    Details
    Dual N-channel dual gate MOSFET
    Source
    An older or alternative marking, from a published code list

    Is it dead? The meter test is below: N-channel MOSFET.

    Datasheetfor BF1210, opens in a new tab
  • DMP2004DMKSOT-23-6P-channel MOSFET, 6 pins, Diodes IncorporatedP-channel MOSFETSOT-23-66 pinsDiodes Incorporated
    What it is
    P-channel MOSFET
    Maker
    Diodes Incorporated
    Package
    SOT-23-6
    Pins
    6
    Source
    Published code list

    Is it dead? The meter test is below: P-channel MOSFET.

  • PDTA115ETSOT-23Digital transistor (PNP, resistors built in), 3 pins, NXPDigital transistor (PNP, resistors built in)SOT-233 pinsNXP
    What it is
    Digital transistor (PNP, resistors built in)
    Maker
    NXP
    Package
    SOT-23
    Pins
    3
    Details
    PNP resistor-equipped transistor; R1 = 100 kΩ, R2 = 100 kΩ
    Source
    Published code list

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

    Datasheetfor PDTA115ET, opens in a new tab
  • RP109N331BSOT-23-5LDO regulator, 5 pins, RicohLDO regulatorSOT-23-55 pinsRicoh
    What it is
    LDO regulator
    Maker
    Ricoh
    Package
    SOT-23-5
    Pins
    5
    Details
    Linear voltage regulator IC: LDO, 3.3V±1%, 150mA, +CE
    Source
    Published code list

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

  • 1 more part has no package on record
    • BC818F-25PNP transistor, AUK SemiconductorPNP transistorNot recordedNot recordedAUK Semiconductor
      What it is
      PNP transistor
      Maker
      AUK Semiconductor
      Package
      Not recorded
      Pins
      Not recorded
      Details
      PNP transistor: AF-Drv, 30V, 800mA, 200mW, B=160..400, 100MHz
      Source
      Published code list

      Is it dead? The meter test is below: PNP 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.

Silicon diode

Diode range, part lifted or one leg off the pad. Red probe on the anode.

Working, it reads

About 0.5 to 0.8 V anode to cathode, and open the other way. Small switching diodes read about 0.6 to 0.7 V; large rectifiers can read a little lower.

Dead, it reads

  • The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
  • Open both ways: failed open.
  • A reading the wrong way round as well: 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 three-pin body can hold two diodes. With a common pin they read two junctions from that pin, just like a transistor; in series they read two drops end to end. Test each pair the datasheet names.

A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

Bipolar 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 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.

PNP transistor

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

Working, it reads

Black 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.

N-channel MOSFET

Diode range, part lifted. Test drain to source first, then short gate to source and test again.

Working, it reads

Red probe on the source, black on the drain: about 0.4 to 0.9 V, the body diode. Open the other way. The gate reads open to both other pins, both ways.

Dead, it reads

  • Drain to source the same both ways, near 0 V with a continuous beep, and still so after shorting gate to source: shorted. The classic failure.
  • The gate reads low to source or drain: gate shorted. Often all three pins end up shorted together.
  • No body diode at all: failed open.
On the board
the gate usually has a resistor to the source, so gate to source reads that resistor, which is not a fault. A drain short can be the load. Lift a leg to be sure.
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 diode range can charge the gate enough to turn the part on, and then drain to source reads near 0 both ways on a good part. Short gate to source and test again before you condemn it.

A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

P-channel MOSFET

Diode range, part lifted. Test drain to source first, then short gate to source and test again.

Working, it reads

Red probe on the drain, black on the source: about 0.4 to 0.9 V, the body diode. Open the other way. The gate reads open to both other pins, both ways.

Dead, it reads

  • Drain to source the same both ways, near 0 V with a continuous beep, and still so after shorting gate to source: shorted. The classic failure.
  • The gate reads low to source or drain: gate shorted. Often all three pins end up shorted together.
  • No body diode at all: failed open.
On the board
the gate usually has a resistor to the source, so gate to source reads that resistor, which is not a fault. Lift a leg to be sure.
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 diode range can charge the gate enough to turn the part on, and then drain to source reads near 0 both ways on a good part. Short gate to source and test again before you condemn it.

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.

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.

Printed with a code easy to misread as PAB

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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