SMD code B-
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.
152 parts are printed B-
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.
WL2817DA30-8DFNLDO regulator, WillsemiLDO regulatorDFNNot recordedWillsemi
- What it is
- LDO regulator
- Maker
- Willsemi
- Package
- DFN
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Voltage regulator.
WNMD2090-6DFNN-channel MOSFET, WillsemiN-channel MOSFETDFNNot recordedWillsemi
- What it is
- N-channel MOSFET
- Maker
- Willsemi
- Package
- DFN
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: N-channel MOSFET.
1SS388PTSOD-5232 pins, Chenmko EnterpriseNot recordedSOD-5232 pinsChenmko Enterprise
- What it is
- Not recorded
- Maker
- Chenmko Enterprise
- Package
- SOD-523
- Pins
- 2
- Details
- Diode: SBD, 40V, 100mA, Vf<0.6V(50mA)
- Source
- Published code list
Is it dead? The meter test is below: Silicon diode.
3SK302SOT-1434 pins, PanNot recordedSOT-1434 pinsPan
- What it is
- Not recorded
- Maker
- Pan
- Package
- SOT-143
- Pins
- 4
- Details
- n-MOS-d: Dual-Gate, UHF, 15V, 30mA, Idss=0..10mA, Up<1,2V
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
AX6901BASOT-323Voltage supervisor, 3 pins, AXElite TechnologyVoltage supervisorSOT-3233 pinsAXElite Technology
- What it is
- Voltage supervisor
- Maker
- AXElite Technology
- Package
- SOT-323
- Pins
- 3
- Details
- Voltage detector IC: 4.38V±1.5%, -Reset PPO
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
AX6903JASOT-323Voltage supervisor, 3 pins, AXElite TechnologyVoltage supervisorSOT-3233 pinsAXElite Technology
- What it is
- Voltage supervisor
- Maker
- AXElite Technology
- Package
- SOT-323
- Pins
- 3
- Details
- Voltage detector IC: 2.80V±1.5%, -Reset PPO
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
BAT15-098SOD-1232 pins, InfineonNot recordedSOD-1232 pinsInfineon
- What it is
- Not recorded
- Maker
- Infineon
- Package
- SOD-123
- Pins
- 2
- Details
- Si-diode: Schottky, 4V, 110mA, Vf<0.32V, <0.35pF; code printed in white
- Source
- Published code list
Is it dead? The meter test is below: Schottky diode.
CH520S-30PTSOD-5232 pins, Chenmko EnterpriseNot recordedSOD-5232 pinsChenmko Enterprise
- What it is
- Not recorded
- Maker
- Chenmko Enterprise
- Package
- SOD-523
- Pins
- 2
- Details
- Diode: SBD, 30V, 200mA, Vf<0.6V(200mA)
- Source
- Published code list
Is it dead? The meter test is below: Silicon diode.
CH3904TPTSOT-416NPN transistor, 3 pins, Chenmko EnterpriseNPN transistorSOT-4163 pinsChenmko Enterprise
- What it is
- NPN transistor
- Maker
- Chenmko Enterprise
- Package
- SOT-416
- Pins
- 3
- Details
- NPN transistor: AF, Sw, 40V, 200mA, B=100..300, 300MHz
- Source
- Published code list
Is it dead? The meter test is below: NPN transistor.
6 more parts have no package on record
VCUT0714A-HD1ESD protection diode, VishayESD protection diodeNot recordedNot recordedVishay
- What it is
- ESD protection diode
- Maker
- Vishay
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Bidirectional Asymmetrical (BiAs) Single Line ESD Protection Diode in LLP1006-2L
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
3SK306N-channel MOSFET, PanasonicN-channel MOSFETNot recordedNot recordedPanasonic
- What it is
- N-channel MOSFET
- Maker
- Panasonic
- Package
- Not recorded
- Pins
- Not recorded
- Details
- MOSFET n-type: Dual gate, UHF-amp, 15V, +30mA, 150mW, Idss=0..10mA
- Source
- Published code list
Is it dead? The meter test is below: N-channel MOSFET.
BB5552 pins, InfineonNot recordedNot recorded2 pinsInfineon
- What it is
- Not recorded
- Maker
- Infineon
- Package
- Not recorded
- Pins
- 2
- Source
- An older or alternative marking, from a published code list
Is it dead? The meter test is below: This part.
BGA123L44 pins, InfineonNot recordedNot recorded4 pinsInfineon
- What it is
- Not recorded
- Maker
- Infineon
- Package
- Not recorded
- Pins
- 4
- Source
- Published code list
Is it dead? The meter test is below: This part.
CH3904T1PTNPN transistor, Chenmko EnterpriseNPN transistorNot recordedNot recordedChenmko Enterprise
- What it is
- NPN transistor
- Maker
- Chenmko Enterprise
- Package
- Not recorded
- Pins
- Not recorded
- Details
- NPN transistor: AF, Sw, 40V, 200mA, B=100..300, 300MHz
- Source
- Published code list
Is it dead? The meter test is below: NPN transistor.
CMBT3904ENPN transistor, Central SemiconductorNPN transistorNot recordedNot recordedCentral Semiconductor
- What it is
- NPN transistor
- Maker
- Central Semiconductor
- Package
- Not recorded
- Pins
- Not recorded
- Details
- NPN transistor: GP, 60V, 200mA, 100mW, B=100..100, 300MHz
- Source
- Published code list
Is it dead? The meter test is below: NPN transistor.
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.
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.
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.
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.
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.
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.
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