SMD code M04
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.
M04 on a chip resistor
40 kΩ
40 kΩ resistor
The M is both the decimal point and the multiplier: 40 kΩ.
Check it with a meter
Lift one end and measure across it. A good one reads 40 kΩ. Measuring it in circuit reads the parallel combination of everything around it, which is almost always lower, never higher: well above 40 kΩ on the board is a fault. Open, or well above 40 kΩ, means it has failed: burnt, cracked or corroded. That does not change what to fit: the marking still says 40 kΩ. 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 (USP-6C, SOT-23-5, SOT-89-5), M04 is a part code instead. Those parts are listed below.
10 parts are printed M04
Not sure which one you have?
Answer up to 4 quick questions and these 10 parts are ranked, with a meter test that settles it. It works on a dead part too.
FM404SMARectifier, 2 pins, LRCRectifierSMA2 pinsLRC
- What it is
- Rectifier
- Maker
- LRC
- Package
- SMA
- Pins
- 2
- Details
- Rectifier, VPK 400 V, IO @ TL 1 A, TL@°C 75
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
FMAF404SMAFRectifier, 2 pins, LRCRectifierSMAF2 pinsLRC
- What it is
- Rectifier
- Maker
- LRC
- Package
- SMAF
- Pins
- 2
- Details
- Rectifier, VPK 400 V, IO @ TL 1 A, TL@°C 75
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
S-FM404SMARectifier, 2 pins, LRCRectifierSMA2 pinsLRC
- What it is
- Rectifier
- Maker
- LRC
- Package
- SMA
- Pins
- 2
- Details
- Rectifier, VPK 400 V, IO @ TL 1 A, TL@°C 75
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
S-FMAF404SMAFRectifier, 2 pins, LRCRectifierSMAF2 pinsLRC
- What it is
- Rectifier
- Maker
- LRC
- Package
- SMAF
- Pins
- 2
- Details
- Rectifier, VPK 400 V, IO @ TL 1 A, TL@°C 75
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
BF904SOT-1434 pins, PhiNot recordedSOT-1434 pinsPhi
- What it is
- Not recorded
- Maker
- Phi
- Package
- SOT-143
- Pins
- 4
- Details
- n-ch uhf dg mosfet
- Source
- Published code list
Is it dead? The meter test is below: N-channel MOSFET.
R3121N034ASOT-23-6Voltage supervisor, 6 pins, RicohVoltage supervisorSOT-23-66 pinsRicoh
- What it is
- Voltage supervisor
- Maker
- Ricoh
- Package
- SOT-23-6
- Pins
- 6
- Details
- Voltage detector IC: 3.4V±1.5%, -Reset ODO
- Source
- Published code list
Is it dead? The meter test is below: Integrated circuit.
4 more parts have no package on record
CFM404Rectifier, LRCRectifierNot recordedNot recordedLRC
- What it is
- Rectifier
- Maker
- LRC
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Rectifier, VPK 400 V, IO @ TL 1 A, TL@°C 75
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
S-CFM404Rectifier, LRCRectifierNot recordedNot recordedLRC
- What it is
- Rectifier
- Maker
- LRC
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Rectifier, VPK 400 V, IO @ TL 1 A, TL@°C 75
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
S-CFM404-SRectifier, LRCRectifierNot recordedNot recordedLRC
- What it is
- Rectifier
- Maker
- LRC
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Rectifier, VPK 400 V, IO @ TL 1 A, TL@°C 75
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
QS6M4Complementary MOSFET pair (N-channel and P-channel), ROHMComplementary MOSFET pair (N-channel and P-channel)Not recordedNot recordedROHM
- What it is
- Complementary MOSFET pair (N-channel and P-channel)
- Maker
- ROHM
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Published code list
Is it dead? The meter test is below: MOSFET pair.
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.
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.
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.
MOSFET pair
Diode range, part lifted. Test drain to source first, then short gate to source and test again. Test each MOSFET on its own pins, as the datasheet's pinout gives them.
Working, it reads
One way between drain and source reads about 0.4 to 0.9 V, the body diode, and the other way open. The gate reads open to both other pins.
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.
- No body diode at all: failed open.
- On the board
- the gate usually has a resistor to the source, which reads as that resistor and 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.
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.
Printed with a code easy to misread as M04
One character differs, and it is one that is easy to confuse under a lamp. Each code has a page of its own.
Codes that begin with M04
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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