SMD code NQ in 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 and published code lists.
1 part in SOT-23 is printed NQ
Not sure which one you have?
Answer up to 4 quick questions and these 6 parts are ranked, with a meter test that settles it. It works on a dead part too.
KRC241SSOT-23Digital transistor (NPN, resistors built in), KECDigital transistor (NPN, resistors built in)KEC
- What it is
- Digital transistor (NPN, resistors built in)
- Maker
- KEC
- Package
- SOT-23
- Pins
- 3
- Details
- NPN transistor: Sw, 50V, 800mA, 200mW, 200MHz, R1/R2=1k/1k
- Source
- Published code list
Is it dead? The meter test is below: Digital transistor.
5 more parts have no package on record. Nothing rules them out, so they stay.
2SCR542F3NPN transistor, ROHMNPN transistorROHM
- What it is
- NPN transistor
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Details
- NPN 3.0A 30V Middle Power Transistor
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: NPN transistor.
TCR2EN125LDO regulator, ToshibaLDO regulatorToshiba
- What it is
- LDO regulator
- Maker
- Toshiba
- Package
- Not recorded
- Pins
- Not recorded
- Details
- TCR2EN series
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Voltage regulator.
2SC6114-QNPN transistor, ROHMNPN transistorROHM
- What it is
- NPN transistor
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Details
- NPN transistor: AF, 50V, 100mA, 150mW, B=120..270, 130MHz
- Source
- Published code list
Is it dead? The meter test is below: NPN transistor.
SiP21107DT-12-E3LDO regulator, VishayLDO regulatorVishay
- What it is
- LDO regulator
- Maker
- Vishay
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Linear voltage regulator IC: LDO, 1.2V±1%, 150mA, +CE, -Error
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
YFZVFH20BZener diode, ROHMZener diodeROHM
- What it is
- Zener diode
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Zener diode: 18.63..19.59V, Izt=10mA, Zzt=28, 500mW
- Source
- Published code list
Is it dead? The meter test is below: Zener diode.
Is it dead? One meter test per kind
Parts of the same kind are tested the same way, so each test is here once. Each part above points to its own.
Digital transistor
Ohms range, part lifted. The datasheet gives the built-in resistors: R1 in series with the base, R2 from base to emitter.
Working, it reads
Base to emitter reads about R1 plus R2 either way round, about 20 kΩ on a 10 k and 10 k part, give or take their wide tolerance. Collector to emitter reads open. A part with no R2 reads a junction behind R1 one way instead.
Dead, it reads
- Collector to emitter the same both ways, near 0 Ω with a continuous beep: shorted.
- From the base, open or far above R1 plus R2: R1 has failed. Static damage shows here most often.
- Base to emitter near 0 Ω: failed short.
- 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:
- The readings depend on the resistor values, so an identical part elsewhere on the board is the surest reference. Measure it the same way.
- Watch for:
- On the diode range a good part with 10 kΩ resistors reads open on every pair, so a good part looks dead there. Use the ohms range.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
NPN transistor
Diode range, part lifted or its base leg off the pad.
Working, it reads
Red probe on the base reads about 0.6 to 0.75 V to the emitter and to the collector, and open the other way round. Collector to emitter reads open both ways.
Dead, it reads
- Collector to emitter the same both ways, near 0 V with a continuous beep: shorted. The commonest failure.
- The base the same both ways to another pin, near 0 V or a middling value: a shorted junction.
- Only one junction reads, or none: a junction has failed open. It then looks like a diode.
- A reading the wrong way round, where it should be open: leaky.
- On the board
- this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
- Compare:
- If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
- Watch for:
- A pair of diodes with a common pin reads just like a transistor, and some transistors carry a built-in diode or resistor. The datasheet says which.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Voltage regulator
Voltage, board powered, black probe on ground. Then ohms with the power off.
Working, it reads
Input pin at the supply, output pin at its rated voltage, and the enable pin high if it has one.
Dead, it reads
- Output equal to the input: the pass element has shorted. Everything after it may have taken the full input.
- Input present, enable high, no output: failed open, or holding itself off into a shorted load. Power off and measure output to ground.
- Power off, input to output near 0 Ω: shorted.
- On the board:
- An output at 0 V is often a shorted load with the regulator in current limit. Lift the output pin: if the short stays on the board, the regulator may be fine.
- Compare:
- The same regulator on another rail or another board shows the right voltages and the right resistances.
- Watch for:
- Makers put input, output and ground on different pins in the same package, so take them from this part's datasheet. Diode or ohms readings between its pins say little; check it powered.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Zener diode
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
- 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.
Printed with a code easy to misread as NQ
One character differs, and it is one that is easy to confuse under a lamp. Each code has a page of its own.
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