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SMD code 509b

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.

509b is a capacitor marking

5 pF

5 pF capacitor

50 followed by the multiplier 9, in picofarads: 5 pF. Printed this way on film and larger ceramic capacitors; small chip ceramics are usually not printed at all. B is the tolerance, ±0.1 pF.

Check it with a meter

Lift one end and measure it on a capacitance range. A good one reads close to 5 pF. In circuit the meter also sees everything connected across it, so the reading means little until it is out. A failed one usually reads near 0 Ω, or a steady low resistance, on the ohms range, often from a crack. On the board a shorted capacitor shorts its whole rail. A failed reading does not change what to fit: the marking still says 5 pF.

On a transistor or diode body (SMA, SOT-23-5, SOT-23-6), 509b is a part code instead. Those parts are listed below.

4 parts are printed 509b

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.

  • G509L25DT11GSOT-23-5Load switch, 5 pins, Global Mixed-mode TechnologyLoad switchSOT-23-55 pinsGlobal Mixed-mode Technology
    What it is
    Load switch
    Maker
    Global Mixed-mode Technology
    Package
    SOT-23-5
    Pins
    5
    Details
    Power Distribution Switch
    Source
    Manufacturer datasheet

    Is it dead? The meter test is below: Load switch.

    Datasheetfor G509L25DT11G, opens in a new tab
  • G509L25DTP1GSOT-23-6Load switch, 6 pins, Global Mixed-mode TechnologyLoad switchSOT-23-66 pinsGlobal Mixed-mode Technology
    What it is
    Load switch
    Maker
    Global Mixed-mode Technology
    Package
    SOT-23-6
    Pins
    6
    Details
    Power Distribution Switch
    Source
    Manufacturer datasheet

    Is it dead? The meter test is below: Load switch.

    Datasheetfor G509L25DTP1G, opens in a new tab
  • SZ509BSMAZener diode, 2 pins, EIC SemiconductorZener diodeSMA2 pinsEIC Semiconductor
    What it is
    Zener diode
    Maker
    EIC Semiconductor
    Package
    SMA
    Pins
    2
    Details
    Z-diode: 9.1V±10%, Izt=82mA, Zzt=2.5Ω, 3W
    Source
    Published code list

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

  • 1 more part has no package on record
    • G509L30DTO1GLoad switch, 5 pins, Global Mixed-mode TechnologyLoad switchNot recorded5 pinsGlobal Mixed-mode Technology
      What it is
      Load switch
      Maker
      Global Mixed-mode Technology
      Package
      Not recorded
      Pins
      5
      Details
      Power Distribution Switch
      Source
      Manufacturer datasheet

      Is it dead? The meter test is below: Load switch.

      Datasheetfor G509L30DTO1G, 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.

Load switch

Voltage, board powered, black probe on ground.

Working, it reads

Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

Dead, it reads

  • Output at the input voltage while switched off: the pass element has shorted.
  • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
On the board:
An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
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 pinout and whether the enable is active high or low differ between parts. 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.

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.

Printed with a code easy to misread as 509b

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

Did you find your part?

Open this in the search to correct a character or try another package.