WhatSMD: identify an unknown SMD component

4 parts are printed KA

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.

BAS16DWSOT-363Switching diode, 6 pins, DiotecSwitching diodeSOT-3636 pinsDiotec
What it is
Switching diode
Maker
Diotec
Package
SOT-363
Pins
6
Details
SMD Small Signal Diode Arrays
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 BAS16DW, opens in a new tab
BSS87SOT-89N-channel MOSFET, 3 pins, NexperiaN-channel MOSFETSOT-893 pinsNexperia
What it is
N-channel MOSFET
Maker
Nexperia
Package
SOT-89
Pins
3
Details
N-Channel Small Signal MOSFET 240 V in SOT-89 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 BSS87, opens in a new tab
PMEG3010EBSOD-523Schottky diode, 2 pins, NexperiaSchottky diodeSOD-5232 pinsNexperia
What it is
Schottky diode
Maker
Nexperia
Package
SOD-523
Pins
2
Details
30 V, 1 A very low VF 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 PMEG3010EB, opens in a new tab
1 more part has no package on record
- BG3130RF amplifier (MMIC), InfineonRF amplifier (MMIC)Not recordedNot recordedInfineon
  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 BG3130, opens in a new tab

20 more parts have codes that begin with KA

Codes that begin with KA

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

BAS16printed KA2SOT-23Switching diode, 3 pins, Diodes IncorporatedSwitching diodeSOT-233 pinsDiodes Incorporated
Printed KA2. 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
Diodes Incorporated
Package
SOT-23
Pins
3
Details
Surface-mount fast switching 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 BAS16, opens in a new tab
BAS16Vprinted KAMSOT-563Switching diode, 6 pins, JSCJSwitching diodeSOT-5636 pinsJSCJ
Printed KAM. 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-563
Pins
6
Details
Switching diode, 75 V, 200 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 BAS16V, opens in a new tab
BAS19printed KA8SOT-23Switching diode, 3 pins, Diodes IncorporatedSwitching diodeSOT-233 pinsDiodes Incorporated
Printed KA8. 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
Diodes Incorporated
Package
SOT-23
Pins
3
Details
Surface-mount fast switching diode (BAS19/BAS20/BAS21 high-voltage family)
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 BAS19, opens in a new tab
BAS19Wprinted KA8SOT-323Switching diode, 3 pins, Taiwan SemiconductorSwitching diodeSOT-3233 pinsTaiwan Semiconductor
Printed KA8. 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
Taiwan Semiconductor
Package
SOT-323
Pins
3
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 BAS19W, opens in a new tab
BAS40Vprinted KANSOT-563Schottky diode, 6 pins, JSCJSchottky diodeSOT-5636 pinsJSCJ
Printed KAN. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Schottky diode
Maker
JSCJ
Package
SOT-563
Pins
6
Details
Schottky diode, 40 V, 0.2 A
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 BAS40V, opens in a new tab
BAT54Vprinted KAVSOT-563Schottky diode, 6 pins, JSCJSchottky diodeSOT-5636 pinsJSCJ
Printed KAV. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Schottky diode
Maker
JSCJ
Package
SOT-563
Pins
6
Details
Schottky diode, 30 V, 0.2 A
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 BAT54V, opens in a new tab
BAT54VLprinted KAVLSOT-563Schottky diode, 6 pins, JSCJSchottky diodeSOT-5636 pinsJSCJ
Printed KAVL. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.
What it is
Schottky diode
Maker
JSCJ
Package
SOT-563
Pins
6
Details
Schottky diode, 30 V, 0.2 A
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 BAT54VL, opens in a new tab
LM2936MP-3.0printed KACASOT-223LDO regulator, 4 pins, Texas InstrumentsLDO regulatorSOT-2234 pinsTexas Instruments
Printed KACA. 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-223
Pins
4
Details
Ultra-Low Quiescent Current LDO Voltage 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 LM2936MP-3.0, opens in a new tab
LM2936MP-3.3printed KABASOT-223LDO regulator, 4 pins, Texas InstrumentsLDO regulatorSOT-2234 pinsTexas Instruments
Printed KABA. 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-223
Pins
4
Details
Ultra-Low Quiescent Current LDO Voltage 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 LM2936MP-3.3, opens in a new tab
LM2936MP-5.0printed KAAASOT-223LDO regulator, 4 pins, Texas InstrumentsLDO regulatorSOT-2234 pinsTexas Instruments
Printed KAAA. 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-223
Pins
4
Details
Ultra-Low Quiescent Current LDO Voltage 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 LM2936MP-5.0, opens in a new tab
LM2936MPX-3.0printed KACASOT-223LDO regulator, 4 pins, Texas InstrumentsLDO regulatorSOT-2234 pinsTexas Instruments
Printed KACA. 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-223
Pins
4
Details
Ultra-Low Quiescent Current LDO Voltage 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 LM2936MPX-3.0, opens in a new tab
LM2936MPX-3.3printed KABASOT-223LDO regulator, 4 pins, Texas InstrumentsLDO regulatorSOT-2234 pinsTexas Instruments
Printed KABA. 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-223
Pins
4
Details
Ultra-Low Quiescent Current LDO Voltage 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 LM2936MPX-3.3, opens in a new tab
LM2936MPX-5.0printed KAAASOT-223LDO regulator, 4 pins, Texas InstrumentsLDO regulatorSOT-2234 pinsTexas Instruments
Printed KAAA. 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-223
Pins
4
Details
Ultra-Low Quiescent Current LDO Voltage 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 LM2936MPX-5.0, opens in a new tab
MMBD914printed KA2SOT-23Switching diode, 3 pins, Diodes IncorporatedSwitching diodeSOT-233 pinsDiodes Incorporated
Printed KA2. 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
Diodes Incorporated
Package
SOT-23
Pins
3
Details
Surface-mount fast switching 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 MMBD914, opens in a new tab
MMBD4148printed KA2SOT-23Switching diode, 3 pins, Diodes IncorporatedSwitching diodeSOT-233 pinsDiodes Incorporated
Printed KA2. 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
Diodes Incorporated
Package
SOT-23
Pins
3
Details
Surface-mount fast switching 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 MMBD4148, opens in a new tab
MMBD4448printed KA3SOT-23Switching diode, 3 pins, JSCJSwitching diodeSOT-233 pinsJSCJ
Printed KA3. 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, 75 V, 250 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 MMBD4448, opens in a new tab
MMBD4448DWprinted KA3SOT-363Switching diode, 6 pins, JSCJSwitching diodeSOT-3636 pinsJSCJ
Printed KA3. 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-363
Pins
6
Details
Switching diode, 75 V, 250 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 MMBD4448DW, opens in a new tab
MMBD4448Vprinted KALSOT-563Switching diode, 6 pins, JSCJSwitching diodeSOT-5636 pinsJSCJ
Printed KAL. 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-563
Pins
6
Details
Switching diode, 80 V, 250 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 MMBD4448V, opens in a new tab
MMBD4448Wprinted KA3SOT-323Switching diode, 3 pins, JSCJSwitching diodeSOT-3233 pinsJSCJ
Printed KA3. 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-323
Pins
3
Details
Switching diode, 75 V, 250 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 MMBD4448W, opens in a new tab
1 more part has no package on record
- MMBD4148CTprinted KA4Switching diode, JSCJSwitching diodeNot recordedNot recordedJSCJ
  Printed KA4. 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
  Not recorded
  Pins
  Not recorded
  Details
  Switching diode, 75 V, 150 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 MMBD4148CT, 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: 2 a month are free without an account, and 3 with a free account.

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?

4 parts are printed KA

Is it dead?

Is it dead?

Is it dead?

Is it dead?

Codes that begin with KA

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?

One code, several parts

When more than one is left

When you cannot read it