SMD marking

Bin SOT-23

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.

21 parts are printed B

Not sure which one you have?

Answer up to 4 quick questions and these 21 parts are ranked, with a meter test that settles it. It works on a dead part too.

IRLMS1503SOT-23N-channel MOSFET, 3 pins, InfineonN-channel MOSFET3 pinsInfineon
What it is
N-channel MOSFET
Maker
Infineon
Package
SOT-23
Pins
3
Details
30V Single N-Channel Power MOSFET in a TSOP-6 (Micro 6) package
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor IRLMS1503, opens in a new tab
20 more parts have no package on record. Nothing rules them out, so they stay.
- AON1606MOSFET, Alpha & Omega SemiconductorMOSFETNot recordedAlpha & Omega Semiconductor
  What it is
  MOSFET
  Maker
  Alpha & Omega Semiconductor
  Package
  Not recorded
  Pins
  Not recorded
  Details
  Low-voltage (12-30 V) MOSFET
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor AON1606, opens in a new tab
- AON1606LMOSFET, Alpha & Omega SemiconductorMOSFETNot recordedAlpha & Omega Semiconductor
  What it is
  MOSFET
  Maker
  Alpha & Omega Semiconductor
  Package
  Not recorded
  Pins
  Not recorded
  Details
  Low-voltage (12-30 V) MOSFET
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor AON1606L, opens in a new tab
- AOZ8S204BLS-03ESD protection diode, Alpha & Omega SemiconductorESD protection diodeNot recordedAlpha & Omega Semiconductor
  What it is
  ESD protection diode
  Maker
  Alpha & Omega Semiconductor
  Package
  Not recorded
  Pins
  Not recorded
  Details
  ESD protection for high-speed interfaces
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor AOZ8S204BLS-03, opens in a new tab
- AOZ8S204BLS-05ESD protection diode, Alpha & Omega SemiconductorESD protection diodeNot recordedAlpha & Omega Semiconductor
  What it is
  ESD protection diode
  Maker
  Alpha & Omega Semiconductor
  Package
  Not recorded
  Pins
  Not recorded
  Details
  ESD protection for high-speed interfaces
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor AOZ8S204BLS-05, opens in a new tab
- AOZ8S322UD2-03ESD protection diode, Alpha & Omega SemiconductorESD protection diodeNot recordedAlpha & Omega Semiconductor
  What it is
  ESD protection diode
  Maker
  Alpha & Omega Semiconductor
  Package
  Not recorded
  Pins
  Not recorded
  Details
  ESD protection for high-speed interfaces
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor AOZ8S322UD2-03, opens in a new tab
- AOZ8829ADI-05ESD protection diode, Alpha & Omega SemiconductorESD protection diodeNot recordedAlpha & Omega Semiconductor
  What it is
  ESD protection diode
  Maker
  Alpha & Omega Semiconductor
  Package
  Not recorded
  Pins
  Not recorded
  Details
  ESD protection for high-speed interfaces
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor AOZ8829ADI-05, opens in a new tab
- BAS16-03WSwitching diode, InfineonSwitching diodeNot recordedInfineon
  What it is
  Switching diode
  Maker
  Infineon
  Package
  Not recorded
  Pins
  Not recorded
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor BAS16-03W, opens in a new tab
- BAT15-098LRHSchottky diode, InfineonSchottky diodeNot recordedInfineon
  What it is
  Schottky diode
  Maker
  Infineon
  Package
  Not recorded
  Pins
  Not recorded
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor BAT15-098LRH, opens in a new tab
- BB555-02VInfineonNot recordedNot recordedInfineon
  What it is
  Not recorded
  Maker
  Infineon
  Package
  Not recorded
  Pins
  Not recorded
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor BB555-02V, opens in a new tab
- ESD5V0AE1ESD protection diode, JSCJESD protection diodeNot recordedJSCJ
  What it is
  ESD protection diode
  Maker
  JSCJ
  Package
  Not recorded
  Pins
  Not recorded
  Details
  ESD protection diode, VRWM 5 V
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor ESD5V0AE1, opens in a new tab
- ESD217-B1-02ELESD protection diode, InfineonESD protection diodeNot recordedInfineon
  What it is
  ESD protection diode
  Maker
  Infineon
  Package
  Not recorded
  Pins
  Not recorded
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor ESD217-B1-02EL, opens in a new tab
- ESDM5V0AE1ESD protection diode, JSCJESD protection diodeNot recordedJSCJ
  What it is
  ESD protection diode
  Maker
  JSCJ
  Package
  Not recorded
  Pins
  Not recorded
  Details
  ESD protection diode, VRWM 5 V
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor ESDM5V0AE1, opens in a new tab
- IRLML2803N-channel MOSFET, InfineonN-channel MOSFETNot recordedInfineon
  What it is
  N-channel MOSFET
  Maker
  Infineon
  Package
  Not recorded
  Pins
  Not recorded
  Details
  30V Single N-Channel Power MOSFET in a Micro 3 package
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor IRLML2803, opens in a new tab
- PJSD05TMESD protection diode, PanjitESD protection diodeNot recordedPanjit
  What it is
  ESD protection diode
  Maker
  Panjit
  Package
  Not recorded
  Pins
  Not recorded
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor PJSD05TM, opens in a new tab
- PS140M-D32ESD protection diode, PanjitESD protection diodeNot recordedPanjit
  What it is
  ESD protection diode
  Maker
  Panjit
  Package
  Not recorded
  Pins
  Not recorded
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor PS140M-D32, opens in a new tab
- SS14MSchottky diode, Taiwan SemiconductorSchottky diodeNot recordedTaiwan Semiconductor
  What it is
  Schottky diode
  Maker
  Taiwan Semiconductor
  Package
  Not recorded
  Pins
  Not recorded
  Details
  Rectifier schottky
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor SS14M, opens in a new tab
- SS14MHSchottky diode, Taiwan SemiconductorSchottky diodeNot recordedTaiwan Semiconductor
  What it is
  Schottky diode
  Maker
  Taiwan Semiconductor
  Package
  Not recorded
  Pins
  Not recorded
  Details
  Rectifier schottky
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor SS14MH, opens in a new tab
- TLV809EA24DPWVoltage supervisor, 5 pins, Texas InstrumentsVoltage supervisor5 pinsTexas Instruments
  What it is
  Voltage supervisor
  Maker
  Texas Instruments
  Package
  Not recorded
  Pins
  5
  Details
  Low Power 250-nA IQ and Small Size Supply Voltage Supervisors
  Source
  From the manufacturer's datasheet
  Is it dead?
  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.
  Datasheetfor TLV809EA24DPW, opens in a new tab
- VCAN33A2-HT5ESD protection diode, VishayESD protection diodeNot recordedVishay
  What it is
  ESD protection diode
  Maker
  Vishay
  Package
  Not recorded
  Pins
  Not recorded
  Details
  Bidirectional Symmetrical (BiSy) Low Capacitance, Dual-Line ESD Protection Diode in DFN1110-3A
  Source
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor VCAN33A2-HT5, opens in a new tab
- VCUT0714A-HD1ESD protection diode, VishayESD protection diodeNot 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
  From the manufacturer's datasheet
  Is it dead?
  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:
  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.
  Datasheetfor VCUT0714A-HD1, opens in a new tab

7 more parts are printed with a code easy to misread as B

Printed with a code easy to misread

One character differs, and it is one that is easy to confuse under a lamp. The odd one out is marked on each.

AOZ8S503BDS-05printed 8ESD protection diode, Alpha & Omega SemiconductorESD protection diodeNot recordedAlpha & Omega Semiconductor
Printed 8 on the part. Easy to misread as B. Check that character with a loupe before you order anything.
What it is
ESD protection diode
Maker
Alpha & Omega Semiconductor
Package
Not recorded
Pins
Not recorded
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor AOZ8S503BDS-05, opens in a new tab
AOZ8S513BDS-05printed 8ESD protection diode, Alpha & Omega SemiconductorESD protection diodeNot recordedAlpha & Omega Semiconductor
Printed 8 on the part. Easy to misread as B. Check that character with a loupe before you order anything.
What it is
ESD protection diode
Maker
Alpha & Omega Semiconductor
Package
Not recorded
Pins
Not recorded
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor AOZ8S513BDS-05, opens in a new tab
AOZ8839DI-05printed 8ESD protection diode, Alpha & Omega SemiconductorESD protection diodeNot recordedAlpha & Omega Semiconductor
Printed 8 on the part. Easy to misread as B. Check that character with a loupe before you order anything.
What it is
ESD protection diode
Maker
Alpha & Omega Semiconductor
Package
Not recorded
Pins
Not recorded
Details
ESD protection for high-speed interfaces
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor AOZ8839DI-05, opens in a new tab
BBY58-02Vprinted 8InfineonNot recordedNot recordedInfineon
Printed 8 on the part. Easy to misread as B. Check that character with a loupe before you order anything.
What it is
Not recorded
Maker
Infineon
Package
Not recorded
Pins
Not recorded
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor BBY58-02V, opens in a new tab
BBY58-03Wprinted 8InfineonNot recordedNot recordedInfineon
Printed 8 on the part. Easy to misread as B. Check that character with a loupe before you order anything.
What it is
Not recorded
Maker
Infineon
Package
Not recorded
Pins
Not recorded
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor BBY58-03W, opens in a new tab
PMEG3005AESFprinted 8Schottky diode, 2 pins, NexperiaSchottky diode2 pinsNexperia
Printed 8 on the part. Easy to misread as B. Check that character with a loupe before you order anything.
What it is
Schottky diode
Maker
Nexperia
Package
Not recorded
Pins
2
Details
30 V, 0.5 A low VF MEGA Schottky barrier rectifier
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor PMEG3005AESF, opens in a new tab
TLV803EA38DPWprinted 8Voltage supervisor, 5 pins, Texas InstrumentsVoltage supervisor5 pinsTexas Instruments
Printed 8 on the part. Easy to misread as B. Check that character with a loupe before you order anything.
What it is
Voltage supervisor
Maker
Texas Instruments
Package
Not recorded
Pins
5
Details
Low Power 250-nA IQ and Small Size Supply Voltage Supervisors
Source
From the manufacturer's datasheet
Is it dead?
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.
Datasheetfor TLV803EA38DPW, opens in a new tab

22 more parts have codes that begin with B

Codes that begin with B

For a marking with its end worn or burnt off. Each one shows its full printed code.

all SOT-23, 3 pins. What differs:

1PS184printed B3TSOT-23Switching diode, NexperiaSwitching diodeNexperia
Printed B3T. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Switching diode
Maker
Nexperia
Package
SOT-23
Pins
3
Details
High-speed double diode
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor 1PS184, opens in a new tab
1SS184printed B3SOT-23Switching diode, JSCJSwitching diodeJSCJ
Printed B3. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Switching diode
Maker
JSCJ
Package
SOT-23
Pins
3
Details
Switching diode, 80 V, 100 mA
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor 1SS184, opens in a new tab
2SB1197Aprinted B97SOT-23Transistor, PanjitTransistorPanjit
Printed B97. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Transistor
Maker
Panjit
Package
SOT-23
Pins
3
Details
Bipolar transistor
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor 2SB1197A, opens in a new tab
2SB1429printed B29SOT-23Transistor, PanjitTransistorPanjit
Printed B29. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Transistor
Maker
Panjit
Package
SOT-23
Pins
3
Details
Bipolar transistor
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor 2SB1429, opens in a new tab
2SC2412Kprinted BQSOT-23NPN transistor, JSCJNPN transistorJSCJ
Printed BQ. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
NPN transistor
Maker
JSCJ
Package
SOT-23
Pins
3
Details
Bipolar transistor, NPN, 50 V, 0.15 A
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor 2SC2412K, opens in a new tab
A1015printed BASOT-23PNP transistor, JSCJPNP transistorJSCJ
Printed BA. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
PNP transistor
Maker
JSCJ
Package
SOT-23
Pins
3
Details
Bipolar transistor, PNP
Source
From the manufacturer's datasheet
Is it dead?
Diode range, part lifted or its base leg off the pad.
Working, it reads
Black 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:
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.
Datasheetfor A1015, opens in a new tab
AO3435printed B5SOT-23P-channel MOSFET, Alpha & Omega SemiconductorP-channel MOSFETAlpha & Omega Semiconductor
Printed B5. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
P-channel MOSFET
Maker
Alpha & Omega Semiconductor
Package
SOT-23
Pins
3
Details
P-channel MOSFET (8-60 V)
Source
From the manufacturer's datasheet
Is it dead?
Diode range, part lifted. Test drain to source first, then short gate to source and test again.
Working, it reads
Red probe on the drain, black on the source: 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:
On the board the gate usually has a resistor to the source, so gate to source reads that resistor, which 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.
Datasheetfor AO3435, opens in a new tab
AO3435Lprinted B5SOT-23P-channel MOSFET, Alpha & Omega SemiconductorP-channel MOSFETAlpha & Omega Semiconductor
Printed B5. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
P-channel MOSFET
Maker
Alpha & Omega Semiconductor
Package
SOT-23
Pins
3
Details
P-channel MOSFET (8-60 V)
Source
From the manufacturer's datasheet
Is it dead?
Diode range, part lifted. Test drain to source first, then short gate to source and test again.
Working, it reads
Red probe on the drain, black on the source: 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:
On the board the gate usually has a resistor to the source, so gate to source reads that resistor, which 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.
Datasheetfor AO3435L, opens in a new tab
AO3442printed BCSOT-23MOSFET, Alpha & Omega SemiconductorMOSFETAlpha & Omega Semiconductor
Printed BC. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
MOSFET
Maker
Alpha & Omega Semiconductor
Package
SOT-23
Pins
3
Details
Medium-voltage (40-400 V) MOSFET
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor AO3442, opens in a new tab
AO3442Lprinted BCSOT-23MOSFET, Alpha & Omega SemiconductorMOSFETAlpha & Omega Semiconductor
Printed BC. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
MOSFET
Maker
Alpha & Omega Semiconductor
Package
SOT-23
Pins
3
Details
Medium-voltage (40-400 V) MOSFET
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor AO3442L, opens in a new tab
AO3451printed BPSOT-23P-channel MOSFET, Alpha & Omega SemiconductorP-channel MOSFETAlpha & Omega Semiconductor
Printed BP. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
P-channel MOSFET
Maker
Alpha & Omega Semiconductor
Package
SOT-23
Pins
3
Details
P-channel MOSFET (8-60 V)
Source
From the manufacturer's datasheet
Is it dead?
Diode range, part lifted. Test drain to source first, then short gate to source and test again.
Working, it reads
Red probe on the drain, black on the source: 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:
On the board the gate usually has a resistor to the source, so gate to source reads that resistor, which 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.
Datasheetfor AO3451, opens in a new tab
AO3452printed BRSOT-23MOSFET, Alpha & Omega SemiconductorMOSFETAlpha & Omega Semiconductor
Printed BR. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
MOSFET
Maker
Alpha & Omega Semiconductor
Package
SOT-23
Pins
3
Details
Low-voltage (12-30 V) MOSFET
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor AO3452, opens in a new tab
AO3453printed BSSOT-23P-channel MOSFET, Alpha & Omega SemiconductorP-channel MOSFETAlpha & Omega Semiconductor
Printed BS. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
P-channel MOSFET
Maker
Alpha & Omega Semiconductor
Package
SOT-23
Pins
3
Details
P-channel MOSFET (8-60 V)
Source
From the manufacturer's datasheet
Is it dead?
Diode range, part lifted. Test drain to source first, then short gate to source and test again.
Working, it reads
Red probe on the drain, black on the source: 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:
On the board the gate usually has a resistor to the source, so gate to source reads that resistor, which 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.
Datasheetfor AO3453, opens in a new tab
AO3454printed BTSOT-23MOSFET, Alpha & Omega SemiconductorMOSFETAlpha & Omega Semiconductor
Printed BT. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
MOSFET
Maker
Alpha & Omega Semiconductor
Package
SOT-23
Pins
3
Details
Low-voltage (12-30 V) MOSFET
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor AO3454, opens in a new tab
AO3456printed BVSOT-23MOSFET, Alpha & Omega SemiconductorMOSFETAlpha & Omega Semiconductor
Printed BV. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
MOSFET
Maker
Alpha & Omega Semiconductor
Package
SOT-23
Pins
3
Details
Low-voltage (12-30 V) MOSFET
Source
From the manufacturer's datasheet
Is it dead?
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:
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.
Datasheetfor AO3456, opens in a new tab
AO3457printed BXSOT-23P-channel MOSFET, Alpha & Omega SemiconductorP-channel MOSFETAlpha & Omega Semiconductor
Printed BX. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
P-channel MOSFET
Maker
Alpha & Omega Semiconductor
Package
SOT-23
Pins
3
Details
P-channel MOSFET (8-60 V)
Source
From the manufacturer's datasheet
Is it dead?
Diode range, part lifted. Test drain to source first, then short gate to source and test again.
Working, it reads
Red probe on the drain, black on the source: 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:
On the board the gate usually has a resistor to the source, so gate to source reads that resistor, which 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.
Datasheetfor AO3457, opens in a new tab
AO3459printed BZSOT-23P-channel MOSFET, Alpha & Omega SemiconductorP-channel MOSFETAlpha & Omega Semiconductor
Printed BZ. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
P-channel MOSFET
Maker
Alpha & Omega Semiconductor
Package
SOT-23
Pins
3
Details
P-channel MOSFET (8-60 V)
Source
From the manufacturer's datasheet
Is it dead?
Diode range, part lifted. Test drain to source first, then short gate to source and test again.
Working, it reads
Red probe on the drain, black on the source: 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:
On the board the gate usually has a resistor to the source, so gate to source reads that resistor, which 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.
Datasheetfor AO3459, opens in a new tab
BCW61Cprinted BCSOT-23PNP transistor, InfineonPNP transistorInfineon
Printed BC. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
PNP transistor
Maker
Infineon
Package
SOT-23
Pins
3
Source
From the manufacturer's datasheet
Is it dead?
Diode range, part lifted or its base leg off the pad.
Working, it reads
Black 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:
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.
Datasheetfor BCW61C, opens in a new tab
BCW61Dprinted BDSOT-23PNP transistor, InfineonPNP transistorInfineon
Printed BD. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
PNP transistor
Maker
Infineon
Package
SOT-23
Pins
3
Source
From the manufacturer's datasheet
Is it dead?
Diode range, part lifted or its base leg off the pad.
Working, it reads
Black 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:
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.
Datasheetfor BCW61D, opens in a new tab
BCX71Hprinted BHSOT-23PNP transistor, InfineonPNP transistorInfineon
Printed BH. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
PNP transistor
Maker
Infineon
Package
SOT-23
Pins
3
Source
From the manufacturer's datasheet
Is it dead?
Diode range, part lifted or its base leg off the pad.
Working, it reads
Black 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:
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.
Datasheetfor BCX71H, opens in a new tab
BCX71Jprinted BJSOT-23PNP transistor, NexperiaPNP transistorNexperia
Printed BJ. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
PNP transistor
Maker
Nexperia
Package
SOT-23
Pins
3
Source
From the manufacturer's datasheet
Is it dead?
Diode range, part lifted or its base leg off the pad.
Working, it reads
Black 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:
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.
Datasheetfor BCX71J, opens in a new tab
BCX71Kprinted BKSOT-23PNP transistor, InfineonPNP transistorInfineon
Printed BK. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
PNP transistor
Maker
Infineon
Package
SOT-23
Pins
3
Source
From the manufacturer's datasheet
Is it dead?
Diode range, part lifted or its base leg off the pad.
Working, it reads
Black 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:
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.
Datasheetfor BCX71K, opens in a new tab

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

21 parts are printed B

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Printed with a code easy to misread

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Codes that begin with B

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?