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SMD code JA in SOD-523

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.

Not sure which one you have?

Answer up to 4 quick questions and these 22 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • BZT52B20WTSOD-523Zener diode, 2 pins, Taitron ComponentsZener diode2 pinsTaitron Components
    What it is
    Zener diode
    Maker
    Taitron Components
    Package
    SOD-523
    Pins
    2
    Details
    Zener diode: 19.60..20.40V, Izt=5.0mA, 200mW
    Source
    Published code list

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

  • MM5ZB20HSOD-523Zener diode, 2 pins, Zowie TechnologyZener diode2 pinsZowie Technology
    What it is
    Zener diode
    Maker
    Zowie Technology
    Package
    SOD-523
    Pins
    2
    Details
    Zener diode: 19.6..20.4V, Zzt=50, Izt=5mA, 200mW
    Source
    Published code list

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

  • RL52Z20SOD-523Zener diode, 2 pins, Ruilong Yuan ElectronicsZener diode2 pinsRuilong Yuan Electronics
    What it is
    Zener diode
    Maker
    Ruilong Yuan Electronics
    Package
    SOD-523
    Pins
    2
    Details
    Zener diode: 19.6..20.4V, Zzt=50, Izt=5mA, 200mW
    Source
    Published code list

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

  • 12 more parts have no package on record. Nothing rules them out, so they stay.
    • BAS21-135Switching diode, Taitron ComponentsSwitching diodeNot recordedTaitron Components
      What it is
      Switching diode
      Maker
      Taitron Components
      Package
      Not recorded
      Pins
      Not recorded
      Details
      SMD Switching Diodes (Three Terminals)
      Source
      Manufacturer datasheet

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

    • BAV70LSwitching diode, VishaySwitching diodeNot recordedVishay
      What it is
      Switching diode
      Maker
      Vishay
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Small Signal Fast Switching Diode
      Source
      Manufacturer datasheet

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

    • BAV70WSSwitching diode, Taitron ComponentsSwitching diodeNot recordedTaitron Components
      What it is
      Switching diode
      Maker
      Taitron Components
      Package
      Not recorded
      Pins
      Not recorded
      Details
      SMD Switching Diodes (Three Terminals)
      Source
      Manufacturer datasheet

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

    • KRA721EDigital transistor (PNP, resistors built in), KECDigital transistor (PNP, resistors built in)Not recordedKEC
      What it is
      Digital transistor (PNP, resistors built in)
      Maker
      KEC
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Manufacturer datasheet

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

    • KRA721UDigital transistor (PNP, resistors built in), KECDigital transistor (PNP, resistors built in)Not recordedKEC
      What it is
      Digital transistor (PNP, resistors built in)
      Maker
      KEC
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Manufacturer datasheet

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

    • LD59030DTPU25RLDO regulator, STMicroelectronicsLDO regulatorNot recordedSTMicroelectronics
      What it is
      LDO regulator
      Maker
      STMicroelectronics
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Manufacturer datasheet

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

    • MM5Z20VBZener diode, Formosa MicrosemiZener diodeNot recordedFormosa Microsemi
      What it is
      Zener diode
      Maker
      Formosa Microsemi
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Manufacturer datasheet

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

    • MM5Z20VB-Q1Zener diode, Formosa MicrosemiZener diodeNot recordedFormosa Microsemi
      What it is
      Zener diode
      Maker
      Formosa Microsemi
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Manufacturer datasheet

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

    • NCP171AMX080075LDO regulator, onsemiLDO regulatorNot recordedonsemi
      What it is
      LDO regulator
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      LDO Regulator - Ultra-Low Iq, Dual Power Mode
      Source
      Manufacturer datasheet

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

    • NCP177AMX070LDO regulator, onsemiLDO regulatorNot recordedonsemi
      What it is
      LDO regulator
      Maker
      onsemi
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Linear Voltage Regulator - Fast Transient Response, Enable
      Source
      Manufacturer datasheet

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

    • TWD21-135WSSwitching diode, Taitron ComponentsSwitching diodeNot recordedTaitron Components
      What it is
      Switching diode
      Maker
      Taitron Components
      Package
      Not recorded
      Pins
      Not recorded
      Details
      SMD Switching Diodes (Two Terminals)
      Source
      Manufacturer datasheet

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

    • WH2508F-3WillsemiNot recordedNot recordedWillsemi
      What it is
      Not recorded
      Maker
      Willsemi
      Package
      Not recorded
      Pins
      Not recorded
      Source
      Manufacturer datasheet

      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.

Zener diode

Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.

Working, it reads

About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.

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, forward too: failed open.
  • Holds well off its rated voltage on the supply test: drifted.
  • A soft knee, or a voltage that creeps on the supply test: 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 meter's diode range stops at about 2 to 3 V, so almost every Zener reads open in reverse on it, good or bad; a 3 V meter may just show a 2.4 or 2.7 V part. Above about 3 V the meter cannot tell a Zener from a plain diode.

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

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.

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.

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.

Codes that begin with JA

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 54 more parts.

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