SMD code 4Fx
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.
The last letter, x, is lower case, which on NXP and Philips parts is a date or factory code, so it was set aside and 4F was searched.
77 parts are printed 4Fx
Not sure which one you have?
Answer up to 4 quick questions and these 50 parts are ranked, with a meter test that settles it. It works on a dead part too.
SBC847BPDXV6SOT-563Complementary transistor pair (NPN and PNP), 6 pins, onsemiComplementary transistor pair (NPN and PNP)SOT-5636 pinsonsemi
- What it is
- Complementary transistor pair (NPN and PNP)
- Maker
- onsemi
- Package
- SOT-563
- Pins
- 6
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Bipolar transistor pair.
2SC4444SOT-233 pins, PanNot recordedSOT-233 pinsPan
- What it is
- Not recorded
- Maker
- Pan
- Package
- SOT-23
- Pins
- 3
- Details
- Si-npn: VHF/IF, 45V, 50mA, 500MHz
- Source
- Published code list
Is it dead? The meter test is below: This part.
APX803L05-17C3SOT-323Voltage supervisor, 3 pins, Diodes IncorporatedVoltage supervisorSOT-3233 pinsDiodes Incorporated
- What it is
- Voltage supervisor
- Maker
- Diodes Incorporated
- Package
- SOT-323
- Pins
- 3
- Details
- Voltage detector IC: 1.7V±1.5%, -Reset ODO, Rdt=55ms
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
ATF-54143SOT-3434 pins, BroadcomNot recordedSOT-3434 pinsBroadcom
- What it is
- Not recorded
- Maker
- Broadcom
- Package
- SOT-343
- Pins
- 4
- Details
- PHEMT .45-6GHz
- Source
- Published code list
Is it dead? The meter test is below: This part.
BC850BWSOT-323Transistor, 3 pins, InfineonTransistorSOT-3233 pinsInfineon
- What it is
- Transistor
- Maker
- Infineon
- Package
- SOT-323
- Pins
- 3
- Details
- Bipolar transistor
- Source
- Published code list
Is it dead? The meter test is below: Bipolar transistor.
10 more parts have no package on record
P4FL43A-AUTVS diode, PanjitTVS diodeNot recordedNot recordedPanjit
- What it is
- TVS diode
- Maker
- Panjit
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
P4HE43ATVS diode, PanjitTVS diodeNot recordedNot recordedPanjit
- What it is
- TVS diode
- Maker
- Panjit
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
P4HE43A-AUTVS diode, PanjitTVS diodeNot recordedNot recordedPanjit
- What it is
- TVS diode
- Maker
- Panjit
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
PESD12VV1BSFESD protection diode, 2 pins, NexperiaESD protection diodeNot recorded2 pinsNexperia
- What it is
- ESD protection diode
- Maker
- Nexperia
- Package
- Not recorded
- Pins
- 2
- Details
- Very low capacitance high voltage bidirectional ESD protection diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
TSCD014WTSchottky diode, Taitron ComponentsSchottky diodeNot recordedNot recordedTaitron Components
- What it is
- Schottky diode
- Maker
- Taitron Components
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Low Profile Chip Type Schottky Rectifier
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
TVD24RWSESD protection diode, Taitron ComponentsESD protection diodeNot recordedNot recordedTaitron Components
- What it is
- ESD protection diode
- Maker
- Taitron Components
- Package
- Not recorded
- Pins
- Not recorded
- Details
- SMD TVS Arrays (Two Terminals)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
TVG24RVAWESD protection diode, Taitron ComponentsESD protection diodeNot recordedNot recordedTaitron Components
- What it is
- ESD protection diode
- Maker
- Taitron Components
- Package
- Not recorded
- Pins
- Not recorded
- Details
- SMD TVS Arrays (Multiple Terminals)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
2SC4971NPN transistor, PanasonicNPN transistorNot recordedNot recordedPanasonic
- What it is
- NPN transistor
- Maker
- Panasonic
- Package
- Not recorded
- Pins
- Not recorded
- Details
- NPN transistor: Sw, 35V, 50mA, 500MHz, B=20..100
- Source
- Published code list
Is it dead? The meter test is below: NPN transistor.
ADP124ARHZ-3.3-R78 pins, Analog DevicesNot recordedNot recorded8 pinsAnalog Devices
- What it is
- Not recorded
- Maker
- Analog Devices
- Package
- Not recorded
- Pins
- 8
- Details
- equivalent [3.3V LDO]
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
AP7341-22FS4-7RLDO regulator, Diodes IncorporatedLDO regulatorNot recordedNot recordedDiodes Incorporated
- What it is
- LDO regulator
- Maker
- Diodes Incorporated
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Linear voltage regulator IC: LDO, 2.2V±1%, 300mA, +CE
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
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.
TVS or ESD protection diode
Diode range, from the protected line to ground, part lifted if you can.
Working, it reads
A one-way part reads about 0.6 to 0.8 V forward and open in reverse. A two-way part reads open both ways. Arrays with several lines read as the datasheet's diagram draws them.
Dead, it reads
- From the line to ground, the same reading both ways, near 0 V with a continuous beep: shorted.
- A reading both ways on a one-way part: leaky.
- A one-way part open both ways: failed open.
- On the board
- , a line reading shorted to ground can be this part or anything else on that line. Lift it: if the short goes with it, it has failed.
- Compare:
- The same part on the next line or connector pin is the healthy reading to compare with.
- Watch for:
- A two-way part reads open both ways when it is good, exactly like one that has failed open. The meter cannot tell them apart; an identical part on the next line can.
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 pair
Diode range, part lifted. Test each transistor on its own pins, as the datasheet's pinout gives them.
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.
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.
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.
NPN transistor
Diode range, part lifted or its base leg off the pad.
Working, it reads
Red 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.
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.
Integrated circuit
Voltage with the board powered; ohms from each pin to ground with it off.
Working, it reads
Supply pin at its voltage and the output doing what the datasheet says. Readings between pins depend on the part.
Dead, it reads
- A pin near 0 Ω to ground or to the supply pin where an identical part does not read that: failed short.
- Supply present, output stuck: failed, or its load has.
- On the board:
- A pin shorted to ground on the board can be anything on that net. Lift the pin to be sure.
- Compare:
- The surest reference is the same IC on a working board, measured pin by pin.
- Watch for:
- Its protection diodes can read like junctions between pins, even like a transistor. That proves nothing either way.
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.
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