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SMD code 4022

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.

4022 on a chip resistor

40.2 kΩ

40.2 kΩ resistor, 1%

402 followed by 2 zeros. Four digits is normally the 1% series.

Check it with a meter

Lift one end and measure across it. A good one reads 40.2 kΩ within 1%. Measuring it in circuit reads the parallel combination of everything around it, which is almost always lower, never higher: well above 40.2 kΩ on the board is a fault. Open, or well above 40.2 kΩ, means it has failed: burnt, cracked or corroded. That does not change what to fit: the marking still says 40.2 kΩ. A burnt resistor usually means the part it feeds drew too much, so find that before fitting a new one.

On a transistor or diode body (SMA, SOT-89), 4022 is a part code instead. Those parts are listed below.

2 parts are printed 4022

Not sure which one you have?

Answer up to 4 quick questions and these 2 parts are ranked, with a meter test that settles it. It works on a dead part too.

  • BL4022SOT-89N-channel MOSFET, 3 pins, Galaxy MicroelectronicsN-channel MOSFETSOT-893 pinsGalaxy Microelectronics
    What it is
    N-channel MOSFET
    Maker
    Galaxy Microelectronics
    Package
    SOT-89
    Pins
    3
    Details
    0.2A, 400V, 1W, N Channel, Power MOSFETs
    Source
    Manufacturer datasheet

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

    Datasheetfor BL4022, opens in a new tab
  • SZ4022SMAZener diode, 2 pins, EIC SemiconductorZener diodeSMA2 pinsEIC Semiconductor
    What it is
    Zener diode
    Maker
    EIC Semiconductor
    Package
    SMA
    Pins
    2
    Details
    Zener diode: 22V±10%, Izt=22.8mA, Zzt=12, 2W
    Source
    Published code list

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

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.

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.

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.

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