SMD code search: identify a part by its marking
1 part is printed Q4U. 9 printed with a similar-looking code.
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.
The only part printed Q4U in our tables
BRBZX84B15Q
- What it is
- Zener diode
- Maker
- Blue Rocket
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead?
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.
Was it this one?
Printed with a code easy to misread
These parts are printed with a character that is easy to misread as what you typed. The odd one out is marked on each.
AD5290YRMZ10printed D4UMSOP-1010 pins, Analog DevicesNot recordedMSOP-1010 pinsAnalog Devices
Printed D4U on the part. Easy to misread as Q4U. Check that character with a loupe before you order anything.
- What it is
- Not recorded
- Maker
- Analog Devices
- Package
- MSOP-10
- Pins
- 10
- Source
- Published code list
Is it dead?
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.
XC66DC3425Mprinted D4USOT-23-55 pins, TorexNot recordedSOT-23-55 pinsTorex
Printed D4U on the part. Easy to misread as Q4U. Check that character with a loupe before you order anything.
- What it is
- Not recorded
- Maker
- Torex
- Package
- SOT-23-5
- Pins
- 5
- Details
- Linear voltage regulator with volatge detector: LDO, 2.5V±2%, 100mA, Vdet=3.4V±2%, +Reset PPO
- Source
- Published code list
Is it dead?
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.
XC66DC3445Mprinted D4USOT-23-55 pins, TorexNot recordedSOT-23-55 pinsTorex
Printed D4U on the part. Easy to misread as Q4U. Check that character with a loupe before you order anything.
- What it is
- Not recorded
- Maker
- Torex
- Package
- SOT-23-5
- Pins
- 5
- Details
- Linear voltage regulator with volatge detector: LDO, 4.5V±2%, 100mA, Vdet=3.4V±2%, +Reset PPO
- Source
- Published code list
Is it dead?
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.
XC66DN3425Mprinted D4USOT-23-55 pins, TorexNot recordedSOT-23-55 pinsTorex
Printed D4U on the part. Easy to misread as Q4U. Check that character with a loupe before you order anything.
- What it is
- Not recorded
- Maker
- Torex
- Package
- SOT-23-5
- Pins
- 5
- Details
- Linear voltage regulator with volatge detector: LDO, 2.5V±2%, 100mA, Vdet=3.4V±2%, +Reset ODO
- Source
- Published code list
Is it dead?
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.
XC66DN3445Mprinted D4USOT-23-55 pins, TorexNot recordedSOT-23-55 pinsTorex
Printed D4U on the part. Easy to misread as Q4U. Check that character with a loupe before you order anything.
- What it is
- Not recorded
- Maker
- Torex
- Package
- SOT-23-5
- Pins
- 5
- Details
- Linear voltage regulator with volatge detector: LDO, 4.5V±2%, 100mA, Vdet=3.4V±2%, +Reset ODO
- Source
- Published code list
Is it dead?
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.
XC6101A526MRprinted 04USOT-23-5Voltage supervisor, 5 pins, TorexVoltage supervisorSOT-23-55 pinsTorex
Printed 04U on the part. Easy to misread as Q4U. Check that character with a loupe before you order anything.
- What it is
- Voltage supervisor
- Maker
- Torex
- Package
- SOT-23-5
- Pins
- 5
- Details
- CMOS-IC: VDet 2.6V, 5%, Hst, -MR, -Reset PPO, Wt=400ms, Rt=3.13ms
- Source
- Published code list
Is it dead?
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.
XC6505C261MRprinted 04USOT-23-5LDO regulator, 5 pins, TorexLDO regulatorSOT-23-55 pinsTorex
Printed 04U on the part. Easy to misread as Q4U. Check that character with a loupe before you order anything.
- What it is
- LDO regulator
- Maker
- Torex
- Package
- SOT-23-5
- Pins
- 5
- Details
- Linear voltage regulator IC: LDO, 2.6V±1%, 200mA, +CE, CL
- Source
- Published code list
Is it dead?
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.
XC6505C261PRprinted 04USOT-89-5LDO regulator, 5 pins, TorexLDO regulatorSOT-89-55 pinsTorex
Printed 04U on the part. Easy to misread as Q4U. Check that character with a loupe before you order anything.
- What it is
- LDO regulator
- Maker
- Torex
- Package
- SOT-89-5
- Pins
- 5
- Details
- Linear voltage regulator IC: LDO, 2.6V±1%, 200mA, +CE, CL
- Source
- Published code list
Is it dead?
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.
1 more part has no package on record
SGM61044AXUGJ6Gprinted 04UDC-DC converter, 6 pins, SG MicroDC-DC converterNot recorded6 pinsSG Micro
Printed 04U on the part. Easy to misread as Q4U. Check that character with a loupe before you order anything.
- What it is
- DC-DC converter
- Maker
- SG Micro
- Package
- Not recorded
- Pins
- 6
- Details
- 2.4V to 5.5V, 4A Synchronous Buck Converter
- Source
- Manufacturer datasheet
Is it dead?
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.
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One code, several parts
Marking codes are not unique. In the standard code book, 6H on a SOT-23 is an NPN transistor, a varicap, an N-channel JFET, two digital transistors, a 3.6 V voltage detector: six parts from five makers. So a search on WhatSMD (What SMD) shows the parts we hold under that code and under codes easily misread as it, with only the columns that tell them apart.
- NPN transistor
- Varicap
- N-channel JFET
- Digital transistor ×2
- 3.6 V voltage detector
When more than one is left
Tap Help me choose. Up to 4 quick answers: whether the part has failed, then what separates the parts left. Those get ranked with the reasoning and a test that settles it. That uses one identification: 2 a month are free without an account, and 3 with a free account.
When you cannot read it
Tap the camera in the field. We read the characters, keep the ones we are unsure of, and search every reading. A photo too soft to read is turned back on your phone first; if it is the only one you can get, you can still send it.
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