SMD code U23 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.
3 parts in SOT-23 are printed U23
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.
2SC2759-23SOT-23RF transistor, 3 pins, NEC ElectronicsRF transistor3 pinsNEC Electronics
- What it is
- RF transistor
- Maker
- NEC Electronics
- Package
- SOT-23
- Pins
- 3
- Details
- NPN transistor: RF-amp, 14V, 50mA, 150mW, B=90..180, 1.5GHz
- Source
- Published code list
Is it dead? The meter test is below: Bipolar transistor.
2SC2759U23SOT-233 pinsNot recorded3 pinsNot recorded
- What it is
- Not recorded
- Maker
- Not recorded
- Package
- SOT-23
- Pins
- 3
- Source
- Published code list
Is it dead? The meter test is below: This part.
UM36523SSOT-23LDO regulator, 3 pins, Union SemiconductorLDO regulator3 pinsUnion Semiconductor
- What it is
- LDO regulator
- Maker
- Union Semiconductor
- Package
- SOT-23
- Pins
- 3
- Details
- Linear voltage regulator IC: LDO, 2.3V±2%, 300mA
- Source
- Published code list
Is it dead? The meter test is below: Voltage regulator.
3 more parts have no package on record. Nothing rules them out, so they stay.
2SC4185RenesasNot recordedNot recordedRenesas
- What it is
- Not recorded
- Maker
- Renesas
- Package
- Not recorded
- Pins
- Not recorded
- Details
- npn RF 10V fT2.4GHz hFE 40-80
- Source
- Published code list
Is it dead? The meter test is below: This part.
QS5U23P-channel MOSFET, ROHMP-channel MOSFETNot recordedROHM
- What it is
- P-channel MOSFET
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Details
- P-Channel MOSFET + Schottky Barrier Diode
- Source
- Published code list
Is it dead? The meter test is below: P-channel MOSFET.
S-8333CAIC-I8T18 pins, ABLICNot recorded8 pinsABLIC
- What it is
- Not recorded
- Maker
- ABLIC
- Package
- Not recorded
- Pins
- 8
- Source
- Published code list
Is it dead? The meter test is below: This part.
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.
Bipolar transistor
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
- 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.
This part
Diode range and ohms range, part lifted.
Working, it reads
Depends on what it is. The datasheet, or an identical part, says.
Dead, it reads
- Between two pins, the same reading both ways, near 0 V with a continuous beep: shorted.
- Open between every pair of pins: failed open, or a part that reads open when working.
- On the board
- this is a first look only: the meter reads every path between those pins, and a short can be a neighbour. Lift one leg before you condemn it.
- Compare:
- If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
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.
P-channel MOSFET
Diode range, part lifted. Test drain to source first, then short gate to source and test again.
Working, it reads
Red probe on the drain, black on the source: about 0.4 to 0.9 V, the body diode. Open the other way. The gate reads open to both other pins, both ways.
Dead, it reads
- Drain to source the same both ways, near 0 V with a continuous beep, and still so after shorting gate to source: shorted. The classic failure.
- The gate reads low to source or drain: gate shorted. Often all three pins end up shorted together.
- No body diode at all: failed open.
- On the board
- the gate usually has a resistor to the source, so gate to source reads that resistor, which is not a fault. Lift a leg to be sure.
- Compare:
- If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
- Watch for:
- The diode range can charge the gate enough to turn the part on, and then drain to source reads near 0 both ways on a good part. Short gate to source and test again before you condemn it.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Codes that begin with U23
For a marking with its end worn or burnt off. Each code has a page of its own.
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