SMD marking

1Min 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.

4 parts are printed 1M

Not sure which one you have?

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

MMBTA13SOT-23Darlington transistor, 3 pins, InfineonDarlington transistor3 pinsInfineon
What it is
Darlington transistor
Maker
Infineon
Package
SOT-23
Pins
3
Details
Darlington transistor, 30 V, 300 mA
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 collector and about 1.1 to 1.4 V to the emitter, two junctions in series, and open the other way round. Collector to emitter reads open. Built-in resistors can change these readings.
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 MMBTA13, opens in a new tab
PMBTA13SOT-23NPN transistor, 3 pins, NexperiaNPN transistor3 pinsNexperia
What it is
NPN transistor
Maker
Nexperia
Package
SOT-23
Pins
3
Details
30 V, 0.5 A NPN Darlington transistor
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 collector and about 1.1 to 1.4 V to the emitter, two junctions in series, and open the other way round. Collector to emitter reads open. Built-in resistors can change these readings.
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 PMBTA13, opens in a new tab
2 more parts have no package on record. Nothing rules them out, so they stay.
- BCM846STransistor, InfineonTransistorNot recordedInfineon
  What it is
  Transistor
  Maker
  Infineon
  Package
  Not recorded
  Pins
  Not recorded
  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 BCM846S, opens in a new tab
- SMBTA13Transistor, InfineonTransistorNot recordedInfineon
  What it is
  Transistor
  Maker
  Infineon
  Package
  Not recorded
  Pins
  Not recorded
  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 SMBTA13, opens in a new tab

1 more part is printed with a code easy to misread as 1M

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.

SMBG16Aprinted LMTVS diode, VishayTVS diodeVishay
Printed LM on the part. Easy to misread as 1M. Check that character with a loupe before you order anything.
What it is
TVS diode
Maker
Vishay
Package
Not recorded
Pins
Not recorded
Details
600 W TVS diode, unidirectional
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 SMBG16A, opens in a new tab

6 more parts have codes that begin with 1M

Codes that begin with 1M

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

REF2025AISDDCprinted 1M98Voltage reference, 5 pins, Texas InstrumentsVoltage reference5 pinsTexas Instruments
Printed 1M98. 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
Not recorded
Pins
5
Details
Low-Drift, Low-Power, Dual-Output, VREF and VREF / 2 Voltage References
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 REF2025AISDDC, opens in a new tab
S1MLprinted 1MLRectifier, Taiwan SemiconductorRectifierNot recordedTaiwan Semiconductor
Printed 1ML. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Rectifier
Maker
Taiwan Semiconductor
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 S1ML, opens in a new tab
S1MLHprinted 1MLRectifier, Taiwan SemiconductorRectifierNot recordedTaiwan Semiconductor
Printed 1ML. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Rectifier
Maker
Taiwan Semiconductor
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 S1MLH, opens in a new tab
S1MLSprinted 1MLSRectifier, Taiwan SemiconductorRectifierNot recordedTaiwan Semiconductor
Printed 1MLS. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Rectifier
Maker
Taiwan Semiconductor
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 S1MLS, opens in a new tab
S1MLSHprinted 1MLSRectifier, Taiwan SemiconductorRectifierNot recordedTaiwan Semiconductor
Printed 1MLS. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Rectifier
Maker
Taiwan Semiconductor
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 S1MLSH, opens in a new tab
LMV324AIDYYprinted LM324IOperational amplifier, 14 pins, Texas InstrumentsOperational amplifier14 pinsTexas Instruments
Printed LM324I. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Operational amplifier
Maker
Texas Instruments
Package
Not recorded
Pins
14
Details
Low-Voltage Rail-to-Rail Output Operational Amplifiers
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 LMV324AIDYY, opens in a new tab

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

4 parts are printed 1M

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Printed with a code easy to misread

Is it dead?

Codes that begin with 1M

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Is it dead?