WhatSMD: identify an unknown SMD component

3 parts are printed 8N

Not sure which one you have?

Answer up to 4 quick questions and these 3 parts are ranked, with a meter test that settles it. It works on a dead part too.

BZD27B7V5P-MSOD-123FZener diode, 2 pins, VishayZener diodeSOD-123F2 pinsVishay
What it is
Zener diode
Maker
Vishay
Package
SOD-123F
Pins
2
Details
7.5 V Zener diode
Source
From the manufacturer's datasheet
Is it dead?
Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.
Working, it reads
About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.
Dead, it reads
The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
Open both ways, forward too: failed open.
Holds well off its rated voltage on the supply test: drifted.
A soft knee, or a voltage that creeps on the supply test: leaky.
On the board:
On the board this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
Compare:
If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
Watch for:
A meter's diode range stops at about 2 to 3 V, so almost every Zener reads open in reverse on it, good or bad; a 3 V meter may just show a 2.4 or 2.7 V part. Above about 3 V the meter cannot tell a Zener from a plain diode.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Datasheetfor BZD27B7V5P-M, opens in a new tab
MM3Z24BSOD-323Zener diode, 2 pins, DiotecZener diodeSOD-3232 pinsDiotec
What it is
Zener diode
Maker
Diotec
Package
SOD-323
Pins
2
Details
SMD Planar Zener Diodes
Source
From the manufacturer's datasheet
Is it dead?
Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.
Working, it reads
About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.
Dead, it reads
The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
Open both ways, forward too: failed open.
Holds well off its rated voltage on the supply test: drifted.
A soft knee, or a voltage that creeps on the supply test: leaky.
On the board:
On the board this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
Compare:
If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
Watch for:
A meter's diode range stops at about 2 to 3 V, so almost every Zener reads open in reverse on it, good or bad; a 3 V meter may just show a 2.4 or 2.7 V part. Above about 3 V the meter cannot tell a Zener from a plain diode.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Datasheetfor MM3Z24B, opens in a new tab
1 more part has no package on record
- TLV74125PDQNLDO regulator, 4 pins, Texas InstrumentsLDO regulatorNot recorded4 pinsTexas Instruments
  What it is
  LDO regulator
  Maker
  Texas Instruments
  Package
  Not recorded
  Pins
  4
  Details
  150-mA, Low-Dropout Regulator With Foldback Current Limit
  Source
  From the manufacturer's datasheet
  Is it dead?
  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.
  Datasheetfor TLV74125PDQN, opens in a new tab

7 more parts are printed with a code easy to misread as 8N

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.

BAT54FN2-AUprinted BNSOD-882Schottky diode, 2 pins, PanjitSchottky diodeSOD-8822 pinsPanjit
Printed BN on the part. Easy to misread as 8N. Check that character with a loupe before you order anything.
What it is
Schottky diode
Maker
Panjit
Package
SOD-882
Pins
2
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 BAT54FN2-AU, opens in a new tab
BZT52H-C15printed BNSOD-123FZener diode, 2 pins, NexperiaZener diodeSOD-123F2 pinsNexperia
Printed BN on the part. Easy to misread as 8N. Check that character with a loupe before you order anything.
What it is
Zener diode
Maker
Nexperia
Package
SOD-123F
Pins
2
Source
From the manufacturer's datasheet
Is it dead?
Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.
Working, it reads
About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.
Dead, it reads
The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
Open both ways, forward too: failed open.
Holds well off its rated voltage on the supply test: drifted.
A soft knee, or a voltage that creeps on the supply test: leaky.
On the board:
On the board this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
Compare:
If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
Watch for:
A meter's diode range stops at about 2 to 3 V, so almost every Zener reads open in reverse on it, good or bad; a 3 V meter may just show a 2.4 or 2.7 V part. Above about 3 V the meter cannot tell a Zener from a plain diode.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Datasheetfor BZT52H-C15, opens in a new tab
5 more parts have no package on record
- AOZ1282CI-1printed BNDC DC converter, Alpha & Omega SemiconductorDC DC converterNot recordedNot recordedAlpha & Omega Semiconductor
  Printed BN on the part. Easy to misread as 8N. Check that character with a loupe before you order anything.
  What it is
  DC DC converter
  Maker
  Alpha & Omega Semiconductor
  Package
  Not recorded
  Pins
  Not recorded
  Details
  Synchronous buck regulator
  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 AOZ1282CI-1, opens in a new tab
- AOZ1282CI-2printed BNDC DC converter, Alpha & Omega SemiconductorDC DC converterNot recordedNot recordedAlpha & Omega Semiconductor
  Printed BN on the part. Easy to misread as 8N. Check that character with a loupe before you order anything.
  What it is
  DC DC converter
  Maker
  Alpha & Omega Semiconductor
  Package
  Not recorded
  Pins
  Not recorded
  Details
  Synchronous buck regulator
  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 AOZ1282CI-2, opens in a new tab
- BGA612printed BNRF amplifier (MMIC), InfineonRF amplifier (MMIC)Not recordedNot recordedInfineon
  Printed BN on the part. Easy to misread as 8N. Check that character with a loupe before you order anything.
  What it is
  RF amplifier (MMIC)
  Maker
  Infineon
  Package
  Not recorded
  Pins
  Not recorded
  Source
  From the manufacturer's datasheet
  Is it dead?
  Voltage, board powered, on the output pin that the bias resistor or choke feeds.
  Working, it reads
  The output pin sits at the device voltage the datasheet gives, a few volts, below the supply.
  Dead, it reads
  Output pin at 0 V, or near 0 Ω to ground with the power off: shorted inside.
  Output pin at the full supply voltage: open inside, no current flowing.
  On the board:
  Measured on the board with power on; the bias network is part of the reading.
  Compare:
  If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
  Watch for:
  The figures depend on the part and its bias resistor. The datasheet gives both.
  A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
  Datasheetfor BGA612, opens in a new tab
- BZX884B47Lprinted BNZener diode, VishayZener diodeNot recordedNot recordedVishay
  Printed BN on the part. Easy to misread as 8N. Check that character with a loupe before you order anything.
  What it is
  Zener diode
  Maker
  Vishay
  Package
  Not recorded
  Pins
  Not recorded
  Details
  47 V Zener diode
  Source
  From the manufacturer's datasheet
  Is it dead?
  Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.
  Working, it reads
  About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.
  Dead, it reads
  The same reading both ways round, near 0 V with a continuous beep or the same middling value: shorted.
  Open both ways, forward too: failed open.
  Holds well off its rated voltage on the supply test: drifted.
  A soft knee, or a voltage that creeps on the supply test: leaky.
  On the board:
  On the board this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
  Compare:
  If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
  Watch for:
  A meter's diode range stops at about 2 to 3 V, so almost every Zener reads open in reverse on it, good or bad; a 3 V meter may just show a 2.4 or 2.7 V part. Above about 3 V the meter cannot tell a Zener from a plain diode.
  A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
  Datasheetfor BZX884B47L, opens in a new tab
- TLV70733DQNprinted BNLDO regulator, 4 pins, Texas InstrumentsLDO regulatorNot recorded4 pinsTexas Instruments
  Printed BN on the part. Easy to misread as 8N. Check that character with a loupe before you order anything.
  What it is
  LDO regulator
  Maker
  Texas Instruments
  Package
  Not recorded
  Pins
  4
  Details
  200-mA, Low-IQ, Low-Noise, Low-Dropout Regulator for Portable Devices
  Source
  From the manufacturer's datasheet
  Is it dead?
  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.
  Datasheetfor TLV70733DQN, opens in a new tab

13 more parts have codes that begin with 8N

Codes that begin with 8N

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

TL4050C50IDCKprinted 8NUSOT-353Voltage reference, 5 pins, Texas InstrumentsVoltage referenceSOT-3535 pinsTexas Instruments
Printed 8NU. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Voltage reference
Maker
Texas Instruments
Package
SOT-353
Pins
5
Details
Precision Micropower Shunt Voltage Reference
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 TL4050C50IDCK, opens in a new tab
74AHCT1G126DCKprinted BN3SOT-353Logic gate, 5 pins, Texas InstrumentsLogic gateSOT-3535 pinsTexas Instruments
Printed BN3. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Logic gate
Maker
Texas Instruments
Package
SOT-353
Pins
5
Details
Single Bus Buffer Gate With 3-State Output
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 74AHCT1G126DCK, opens in a new tab
ESDBNJ12VS2printed BNJ12SOT-23ESD protection diode, 3 pins, JSCJESD protection diodeSOT-233 pinsJSCJ
Printed BNJ12. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
ESD protection diode
Maker
JSCJ
Package
SOT-23
Pins
3
Details
ESD protection diode, VRWM 12 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 ESDBNJ12VS2, opens in a new tab
LMT84DCKprinted BNASOT-353Temperature sensor, 5 pins, Texas InstrumentsTemperature sensorSOT-3535 pinsTexas Instruments
Printed BNA. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Temperature sensor
Maker
Texas Instruments
Package
SOT-353
Pins
5
Details
1.5-V, SC70/TO-92/TO-92S, Analog Temperature Sensors
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 LMT84DCK, opens in a new tab
P4SMA27printed BNJSMATVS diode, 2 pins, Taiwan SemiconductorTVS diodeSMA2 pinsTaiwan Semiconductor
Printed BNJ. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
TVS diode
Maker
Taiwan Semiconductor
Package
SMA
Pins
2
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 P4SMA27, opens in a new tab
P4SMA27Hprinted BNJSMATVS diode, 2 pins, Taiwan SemiconductorTVS diodeSMA2 pinsTaiwan Semiconductor
Printed BNJ. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
TVS diode
Maker
Taiwan Semiconductor
Package
SMA
Pins
2
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 P4SMA27H, opens in a new tab
SN74AHCT1G126DCKprinted BNLSOT-353Logic gate, 5 pins, Texas InstrumentsLogic gateSOT-3535 pinsTexas Instruments
Printed BNL. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Logic gate
Maker
Texas Instruments
Package
SOT-353
Pins
5
Details
Single Bus Buffer Gate With 3-State Output
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 SN74AHCT1G126DCK, opens in a new tab
TPS71523DCKprinted BNXSOT-353LDO regulator, 5 pins, Texas InstrumentsLDO regulatorSOT-3535 pinsTexas Instruments
Printed BNX. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
LDO regulator
Maker
Texas Instruments
Package
SOT-353
Pins
5
Details
50-mA, 24-V, 3.2-μA Quiescent Current, Low-Dropout Linear Regulator
Source
From the manufacturer's datasheet
Is it dead?
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.
Datasheetfor TPS71523DCK, opens in a new tab
TPS71730DCKprinted BNASOT-353LDO regulator, 5 pins, Texas InstrumentsLDO regulatorSOT-3535 pinsTexas Instruments
Printed BNA. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
LDO regulator
Maker
Texas Instruments
Package
SOT-353
Pins
5
Details
Low-Noise, High-Bandwidth PSRR, Low-Dropout, 150-mA Linear Regulator
Source
From the manufacturer's datasheet
Is it dead?
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.
Datasheetfor TPS71730DCK, opens in a new tab
TPS71733DCKprinted BNBSOT-353LDO regulator, 5 pins, Texas InstrumentsLDO regulatorSOT-3535 pinsTexas Instruments
Printed BNB. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
LDO regulator
Maker
Texas Instruments
Package
SOT-353
Pins
5
Details
Low-Noise, High-Bandwidth PSRR, Low-Dropout, 150-mA Linear Regulator
Source
From the manufacturer's datasheet
Is it dead?
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.
Datasheetfor TPS71733DCK, opens in a new tab
TPS71733DRVprinted BNBWSONLDO regulator, 6 pins, Texas InstrumentsLDO regulatorWSON6 pinsTexas Instruments
Printed BNB. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
LDO regulator
Maker
Texas Instruments
Package
WSON
Pins
6
Details
Low-Noise, High-Bandwidth PSRR, Low-Dropout, 150-mA Linear Regulator
Source
From the manufacturer's datasheet
Is it dead?
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.
Datasheetfor TPS71733DRV, opens in a new tab
TPS715345DCKprinted BNYSOT-353LDO regulator, 5 pins, Texas InstrumentsLDO regulatorSOT-3535 pinsTexas Instruments
Printed BNY. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
LDO regulator
Maker
Texas Instruments
Package
SOT-353
Pins
5
Details
50-mA, 24-V, 3.2-μA Quiescent Current, Low-Dropout Linear Regulator
Source
From the manufacturer's datasheet
Is it dead?
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.
Datasheetfor TPS715345DCK, opens in a new tab
1 more part has no package on record
- ESDBNB5V0B1printed BNB5ESD protection diode, JSCJESD protection diodeNot recordedNot recordedJSCJ
  Printed BNB5. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
  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 ESDBNB5V0B1, opens in a new tab

One code, several parts

Marking codes are not unique. In the standard code book, 6H on a SOT-23 is an NPN transistor, a varicap, an N-channel JFET, two digital transistors, a 3.6 V voltage detector: six parts from five makers. So a search shows the parts we hold under that code and under codes easily misread as it, with only the columns that tell them apart.

6Hon a SOT-23, in the code book

NPN transistor
Varicap
N-channel JFET
Digital transistor ×2
3.6 V voltage detector

When more than one is left

Tap Help me choose. Up to 4 quick answers: whether the part has failed, then what separates the parts left. Those get ranked with the reasoning and a test that settles it. That uses one identification; 3 a month are free.

When you cannot read it

Tap the camera in the field. We read the characters, keep the ones we are unsure of, and search every reading. A photo too soft to read is turned back on your phone first; if it is the only one you can get, you can still send it.

What’s printed on it?

3 parts are printed 8N

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 8N

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?

One code, several parts

When more than one is left

When you cannot read it