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SMD code search: identify a part by its marking

2 parts are printed IJP. 3 printed with a similar-looking code.

2 parts are printed IJP

Not sure which one you have?

Answer up to 4 quick questions and these 2 parts are ranked, with a meter test that settles it. It works on a dead part too.

LDO regulator, all WSON, all Leadtrend.

  • LD6918GDAW-JPWSON
    What it is
    LDO regulator
    Maker
    Leadtrend
    Package
    WSON
    Pins
    Not recorded
    Details
    Linear voltage regulator IC: LDO, Dual out, Vout1/Vout2=1.7V/2.3V±1%, 300mA, +CE
    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.

  • LD6918GDDW-JPWSON
    What it is
    LDO regulator
    Maker
    Leadtrend
    Package
    WSON
    Pins
    Not recorded
    Details
    Linear voltage regulator IC: LDO, Dual out, Vout1/Vout2=1.7V/2.3V±1%, 300mA, +CE
    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.

3 more parts are printed with a code easy to misread as IJP

Printed with a code easy to misread

One character differs, and it is one that is easy to confuse under a lamp. The odd one out is marked on each.

  • BC848Aprinted 1JpSOT-23NPN transistor, 3 pins, PhilipsNPN transistorSOT-233 pinsPhilips

    Printed 1Jp on the part. Easy to misread as IJP. Check that character with a loupe before you order anything.

    What it is
    NPN transistor
    Maker
    Philips
    Package
    SOT-23
    Pins
    3
    Details
    30 V NPN small-signal transistor, gain group A
    Source
    Published code list

    Is it dead?

    Diode range, part lifted or its base leg off the pad.

    Working, it reads

    Red probe on the base 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.

    Datasheetfor BC848A, opens in a new tab
  • BF579printed LJpSOT-233 pins, PhiNot recordedSOT-233 pinsPhi

    Printed LJp on the part. Easy to misread as IJP. Check that character with a loupe before you order anything.

    What it is
    Not recorded
    Maker
    Phi
    Package
    SOT-23
    Pins
    3
    Details
    Si-pnp: VHF/UHF, 20V, 25mA, 200mW, B=20..90, 1.75GHz
    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.

  • LD6991AGU-1723printed LJPSOT-3636 pins, LeadtrendNot recordedSOT-3636 pinsLeadtrend

    Printed LJP on the part. Easy to misread as IJP. Check that character with a loupe before you order anything.

    What it is
    Not recorded
    Maker
    Leadtrend
    Package
    SOT-363
    Pins
    6
    Details
    Linear voltage regulator with volatge detector: LDO, 1.7V±2%, 90mA, Vdet=2.3V±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.

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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.

6Hon a SOT-23, in the code book
  • 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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