SMD code 42
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.
7 parts are printed 42
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.
AO6402ASOT-23-6MOSFET, 6 pins, Alpha & Omega SemiconductorMOSFETSOT-23-66 pinsAlpha & Omega Semiconductor
- What it is
- MOSFET
- Maker
- Alpha & Omega Semiconductor
- Package
- SOT-23-6
- Pins
- 6
- Details
- Low-voltage (12-30 V) MOSFET
- Source
- From the manufacturer's datasheet
Is it dead? The meter test is below: MOSFET.
AO6402ALSOT-23-6MOSFET, 6 pins, Alpha & Omega SemiconductorMOSFETSOT-23-66 pinsAlpha & Omega Semiconductor
- What it is
- MOSFET
- Maker
- Alpha & Omega Semiconductor
- Package
- SOT-23-6
- Pins
- 6
- Details
- Low-voltage (12-30 V) MOSFET
- Source
- From the manufacturer's datasheet
Is it dead? The meter test is below: MOSFET.
BAT54AWSOT-323Schottky diode, 3 pins, NexperiaSchottky diodeSOT-3233 pinsNexperia
- What it is
- Schottky diode
- Maker
- Nexperia
- Package
- SOT-323
- Pins
- 3
- Pinout
- 1 cathode of diode 1
- 2 cathode of diode 2
- 3 common anode
- Details
- 30 V surface-mount Schottky barrier diode, dual common anode
- Source
- From the manufacturer's datasheet
Is it dead? The meter test is below: Schottky diode.
BZX384-A75SOD-323Zener diode, 2 pins, NexperiaZener diodeSOD-3232 pinsNexperia
- What it is
- Zener diode
- Maker
- Nexperia
- Package
- SOD-323
- Pins
- 2
- Source
- From the manufacturer's datasheet
Is it dead? The meter test is below: Zener diode.
PDTA123EUSOT-323Digital transistor (PNP, resistors built in), 3 pins, NexperiaDigital transistor (PNP, resistors built in)SOT-3233 pinsNexperia
- What it is
- Digital transistor (PNP, resistors built in)
- Maker
- Nexperia
- Package
- SOT-323
- Pins
- 3
- Details
- PNP resistor-equipped transistor; R1 = 2.2 kΩ, R2 = 2.2 kΩ
- Source
- From the manufacturer's datasheet
Is it dead? The meter test is below: Digital transistor.
EIA-96:420603Precision resistor (EIA-96 code), 2 pinsPrecision resistor (EIA-96 code)06032 pinsNot recorded
- What it is
- Precision resistor (EIA-96 code)
- Maker
- Not recorded
- Package
- 0603
- Pins
- 2
- Details
- EIA-96 precision chip resistor, significand 26.7; the printed mark adds a multiplier letter (42A = 267 Ohm, 42B = 2.67 kOhm)
- Source
- Added by hand from a published table
Is it dead? The meter test is below: Resistor.
1 more part has no package on record
BGC420RF amplifier (MMIC), InfineonRF amplifier (MMIC)Not recordedNot recordedInfineon
- What it is
- RF amplifier (MMIC)
- Maker
- Infineon
- Package
- Not recorded
- Pins
- Not recorded
- Source
- From the manufacturer's datasheet
Is it dead? The meter test is below: RF amplifier.
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.
MOSFET
Diode range, part lifted. Test drain to source first, then short gate to source and test again.
Working, it reads
One way between drain and source reads about 0.4 to 0.9 V, the body diode, and the other way open. The gate reads open to both other pins.
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.
- No body diode at all: failed open.
- On the board
- the gate usually has a resistor to the source, which reads as that resistor and 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.
Schottky diode
Diode range, part lifted or one leg off the pad. Red probe on the anode.
Working, it reads
About 0.15 to 0.45 V anode to cathode, roughly half a silicon diode, and open the other way.
Dead, it reads
- The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
- A reading the wrong way round as well: leaky.
- Open both ways: failed open.
- 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 large Schottky can read about 0.1 V forward and beep like a short, and leaks a little the wrong way when good, more when warm. It is shorted only if it reads the same both ways. Measure it cold, beside an identical cold one.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
RF amplifier
Voltage, board powered, on the output pin that the bias resistor or choke feeds.
Working, it reads
The output pin sits at the device voltage the datasheet gives, a few volts, below the supply.
Dead, it reads
- Output pin at 0 V, or near 0 Ω to ground with the power off: shorted inside.
- Output pin at the full supply voltage: open inside, no current flowing.
- On the board:
- Measured on the board with power on; the bias network is part of the reading.
- 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 figures depend on the part and its bias resistor. 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.
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.
Resistor
Ohms range, across it, power off.
Working, it reads
Its marked value, within tolerance. On the board it reads the same or lower, because everything around it sits in parallel.
Dead, it reads
- Open: burnt, cracked, or eaten through by sulphur. The commonest failure.
- Well above its marked value: drifted high.
- On the board, clearly higher than its marked value: it has failed, since the board can only pull a reading down.
- On the board:
- A reading lower than marked on the board proves nothing; lift one end. A reading higher than marked is a fault even on the board.
- Compare:
- The same position on another channel usually carries the same value, and so does the matching part on another board.
- Watch for:
- A burnt resistor usually means the part it feeds pulled too much. Find that before fitting a new one, or it burns too. The marking, not the reading, says what to fit.
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 42
One character differs, and it is one that is easy to confuse under a lamp. Each code has a page of its own.
Codes that begin with 42
For a marking with its end worn or burnt off. Each code has a page of its own.
Open this in the search to correct a character or try another package.