SMD code JJ- 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.
10 parts in SOT-23 are printed JJ-
Not sure which one you have?
Answer up to 4 quick questions and these 30 parts are ranked, with a meter test that settles it. It works on a dead part too.
15 parts have no package on record. Nothing rules them out, so they stay.
RQ5C035BCP-channel MOSFET, ROHMP-channel MOSFETROHM
- What it is
- P-channel MOSFET
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Pch -20V -3.5A Middle Power MOSFET
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: P-channel MOSFET.
RW4C045BCP-channel MOSFET, ROHMP-channel MOSFETROHM
- What it is
- P-channel MOSFET
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Pch -20V -4.5A Power MOSFET
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: P-channel MOSFET.
SCS70DSTL-CSwitching diode, SeCoSSwitching diodeSeCoS
- What it is
- Switching diode
- Maker
- SeCoS
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
2SJ416Sanyo ElectricNot recordedSanyo Electric
- What it is
- Not recorded
- Maker
- Sanyo Electric
- Package
- Not recorded
- Pins
- Not recorded
- Details
- p-MOS*-e: Sw, U-Speed, LogL, 30V, 2A, 1.5W, 10/110nS
- Source
- Published code list
Is it dead? The meter test is below: This part.
2SK1839N-channel MOSFET, Sanyo ElectricN-channel MOSFETSanyo Electric
- What it is
- N-channel MOSFET
- Maker
- Sanyo Electric
- Package
- Not recorded
- Pins
- Not recorded
- Details
- MOSFET n-type: Sw, 30V, 100mA, 150mW, <15(10mA), 12pF
- Source
- Published code list
Is it dead? The meter test is below: N-channel MOSFET.
2SK1840N-channel MOSFET, Sanyo ElectricN-channel MOSFETSanyo Electric
- What it is
- N-channel MOSFET
- Maker
- Sanyo Electric
- Package
- Not recorded
- Pins
- Not recorded
- Details
- MOSFET n-type: Sw, 30V, 100mA, 200mW, <15(10mA), 12pF
- Source
- Published code list
Is it dead? The meter test is below: N-channel MOSFET.
BU4841FVoltage supervisor, ROHMVoltage supervisorROHM
- What it is
- Voltage supervisor
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Details
- CMOS-IC: Voltage Detector 4,1V, -Reset Open drain output
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
BU4841FWEVoltage supervisor, ROHMVoltage supervisorROHM
- What it is
- Voltage supervisor
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Details
- CMOS-IC: Voltage Detector 4,1V, -Reset Open drain output
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
BU4841GVoltage supervisor, ROHMVoltage supervisorROHM
- What it is
- Voltage supervisor
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Details
- CMOS-IC: Voltage Detector 4,1V, -Reset Open drain output
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
DRC9A14YDigital transistor (NPN, resistors built in), PanasonicDigital transistor (NPN, resistors built in)Panasonic
- What it is
- Digital transistor (NPN, resistors built in)
- Maker
- Panasonic
- Package
- Not recorded
- Pins
- Not recorded
- Details
- NPN transistor: Sw, 50V, 80mA, 125mW, R1/R2=10k/47k
- Source
- Published code list
Is it dead? The meter test is below: Digital transistor.
KRA729EKECNot recordedKEC
- What it is
- Not recorded
- Maker
- KEC
- Package
- Not recorded
- Pins
- Not recorded
- Details
- PNP transistor: Dual, Sw, 50V, 100mA, 200mW, R1/R2=47k/22k
- Source
- Published code list
Is it dead? The meter test is below: Bipolar transistor.
KRA729UKECNot recordedKEC
- What it is
- Not recorded
- Maker
- KEC
- Package
- Not recorded
- Pins
- Not recorded
- Details
- PNP transistor: Dual, Sw, 50V, 100mA, 200mW, R1/R2=47k/22k
- Source
- Published code list
Is it dead? The meter test is below: Bipolar transistor.
KRC659FKECNot recordedKEC
- What it is
- Not recorded
- Maker
- KEC
- Package
- Not recorded
- Pins
- Not recorded
- Details
- NPN transistor: Dual, Sw, 20V, 50mA, 50mW, R1/R2=47k/22k
- Source
- Published code list
Is it dead? The meter test is below: Bipolar transistor.
NC7SZ02LFairchild SemiconductorNot recordedFairchild Semiconductor
- What it is
- Not recorded
- Maker
- Fairchild Semiconductor
- Package
- Not recorded
- Pins
- Not recorded
- Details
- CMOS logic IC: 2-input NOR gate
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
RT9526GQWBattery charger, RichtekBattery chargerRichtek
- What it is
- Battery charger
- Maker
- Richtek
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
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.
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.
Silicon diode
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
- 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.
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.
N-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 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
- 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.
Integrated circuit
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.
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.
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.
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