SMD code R4 in SOD-123
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.
R4 on a chip resistor
0.4 Ω
0.4 Ω resistor
The R stands in for the decimal point, which is how sub-ohm and fractional values are printed.
Check it with a meter
Lift one end and measure across it. A good one reads 0.4 Ω. Measuring it in circuit reads the parallel combination of everything around it, which is almost always lower, never higher: well above 0.4 Ω on the board is a fault. Open, or well above 0.4 Ω, means it has failed: burnt, cracked or corroded. That does not change what to fit: the marking still says 0.4 Ω. A burnt resistor usually means the part it feeds drew too much, so find that before fitting a new one.
On a transistor or diode body (SOT-23-5, SOT-23, SOT-89), R4 is a part code instead. Those parts are listed below.
7 parts in SOD-123 are printed R4
Not sure which one you have?
Answer up to 4 quick questions and these 29 parts are ranked, with a meter test that settles it. It works on a dead part too.
BZT52B6V2SOD-123Zener diode, 2 pins, YFWZener diodeSOD-1232 pinsYFW
- What it is
- Zener diode
- Maker
- YFW
- Package
- SOD-123
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
GSMBR0540SOD-123Schottky diode, 2 pins, Good-ArkSchottky diodeSOD-1232 pinsGood-Ark
- What it is
- Schottky diode
- Maker
- Good-Ark
- Package
- SOD-123
- Pins
- 2
- Details
- Schottky diode, 40 V, 500 mA
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
MM1Z6V2BWSOD-123Zener diode, 2 pins, YFWZener diodeSOD-1232 pinsYFW
- What it is
- Zener diode
- Maker
- YFW
- Package
- SOD-123
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
WSR4005D1SOD-123Schottky diode, 2 pins, WayonSchottky diodeSOD-1232 pinsWayon
- What it is
- Schottky diode
- Maker
- Wayon
- Package
- SOD-123
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
ZT52B6V2SOD-123Zener diode, 2 pins, YFWZener diodeSOD-1232 pinsYFW
- What it is
- Zener diode
- Maker
- YFW
- Package
- SOD-123
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
MM1Z5236BHSOD-123Zener diode, 2 pins, Zowie TechnologyZener diodeSOD-1232 pinsZowie Technology
- What it is
- Zener diode
- Maker
- Zowie Technology
- Package
- SOD-123
- Pins
- 2
- Details
- Zener diode: 7.13..7.88V, Izt=20mA, Zzt=6, 500mW
- Source
- Published code list
Is it dead? The meter test is below: Zener diode.
MMSZ5236BSOD-123FZener diode, 2 pins, DiotecZener diodeSOD-123F2 pinsDiotec
- What it is
- Zener diode
- Maker
- Diotec
- Package
- SOD-123F
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
8 more parts have no package on record. Nothing rules them out, so they stay.
GSBA1040LPSchottky diode, Good-ArkSchottky diodeNot recordedNot recordedGood-Ark
- What it is
- Schottky diode
- Maker
- Good-Ark
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Schottky diode, 40 V, 1 A
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
LM3404N-channel MOSFET, LeiditechN-channel MOSFETNot recordedNot recordedLeiditech
- What it is
- N-channel MOSFET
- Maker
- Leiditech
- Package
- Not recorded
- Pins
- Not recorded
- Details
- N-channel MOSFET, 30 V, 5.6 A
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: N-channel MOSFET.
2SC4092RD4 pins, RenesasNot recordedNot recorded4 pinsRenesas
- What it is
- Not recorded
- Maker
- Renesas
- Package
- Not recorded
- Pins
- 4
- Source
- Published code list
Is it dead? The meter test is below: This part.
74AXP2T3407DCNXPNot recordedNot recordedNot recordedNXP
- What it is
- Not recorded
- Maker
- NXP
- Package
- Not recorded
- Pins
- Not recorded
- Details
- CMOS logic IC: Single buffer and buffer with open-drain output
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
74AXP2T3407GNNXPNot recordedNot recordedNot recordedNXP
- What it is
- Not recorded
- Maker
- NXP
- Package
- Not recorded
- Pins
- Not recorded
- Details
- CMOS logic IC: Single buffer and buffer with open-drain output
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
74AXP2T3407GSNXPNot recordedNot recordedNot recordedNXP
- What it is
- Not recorded
- Maker
- NXP
- Package
- Not recorded
- Pins
- Not recorded
- Details
- CMOS logic IC: Single buffer and buffer with open-drain output
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
74AXP2T3407GTNXPNot recordedNot recordedNot recordedNXP
- What it is
- Not recorded
- Maker
- NXP
- Package
- Not recorded
- Pins
- Not recorded
- Details
- CMOS logic IC: Single buffer and buffer with open-drain output
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
BD46E282G-MVoltage supervisor, ROHMVoltage supervisorNot recordedNot recordedROHM
- What it is
- Voltage supervisor
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Voltage detector IC: 2.8V±1%, -MR, -Reset PPO, Rdt=200ms
- 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.
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.
Schottky diode
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
- 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.
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.
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.
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.
Codes that begin with R4
For a marking with its end worn or burnt off. Each code has a page of its own.
Codes not listed here are printed on 20 more parts.
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