demotest installation
Skip to content
WhatSMDSign in

2 parts are printed DD. 4 printed with a similar-looking code.

2 parts are printed DD

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.

  • BFN16RF transistor, Infineon
    What it is
    RF transistor
    Maker
    Infineon
    Package
    Not recorded
    Pins
    Not recorded
    Source
    From the manufacturer's datasheet

    Is it dead?

    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:
    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 BFN16, opens in a new tab
  • ESD321DPYESD protection diode, 2 pins, Texas Instruments
    What it is
    ESD protection diode
    Maker
    Texas Instruments
    Package
    Not recorded
    Pins
    2
    Details
    1-Channel 30kV ESD Protection Diode with Low Capacitance (< 1pF) in 0402 and SOD-523 Packages
    Source
    From the manufacturer's datasheet

    Is it dead?

    Diode range, from the protected line to ground, part lifted if you can.

    Working, it reads

    A one-way part reads about 0.6 to 0.8 V forward and open in reverse. A two-way part reads open both ways. Arrays with several lines read as the datasheet's diagram draws them.

    Dead, it reads

    • From the line to ground, the same reading both ways, near 0 V with a continuous beep: shorted.
    • A reading both ways on a one-way part: leaky.
    • A one-way part open both ways: failed open.
    On the board:
    On the board, a line reading shorted to ground can be this part or anything else on that line. Lift it: if the short goes with it, it has failed.
    Compare:
    The same part on the next line or connector pin is the healthy reading to compare with.
    Watch for:
    A two-way part reads open both ways when it is good, exactly like one that has failed open. The meter cannot tell them apart; an identical part on the next line can.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

    Datasheetfor ESD321DPY, opens in a new tab
4 more parts are printed with a code easy to misread as DD

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.

  • AO6400printed D0SOT-23-6MOSFET, 6 pins, Alpha & Omega Semiconductor

    Printed D0 on the part. Easy to misread as DD. Check that character with a loupe before you order anything.

    What it is
    MOSFET
    Maker
    Alpha & Omega Semiconductor
    Package
    SOT-23-6
    Pins
    6
    Details
    Low-voltage (12-30 V) MOSFET
    Source
    From the manufacturer's datasheet

    Is it dead?

    Diode range, part lifted. Test drain to source first, then short gate to source and test again.

    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:
    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.

    Datasheetfor AO6400, opens in a new tab
  • AO6400Lprinted D0SOT-23-6MOSFET, 6 pins, Alpha & Omega Semiconductor

    Printed D0 on the part. Easy to misread as DD. Check that character with a loupe before you order anything.

    What it is
    MOSFET
    Maker
    Alpha & Omega Semiconductor
    Package
    SOT-23-6
    Pins
    6
    Details
    Low-voltage (12-30 V) MOSFET
    Source
    From the manufacturer's datasheet

    Is it dead?

    Diode range, part lifted. Test drain to source first, then short gate to source and test again.

    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:
    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.

    Datasheetfor AO6400L, opens in a new tab
  • 2 more parts have no package on record. Nothing rules them out, so they stay.
    • BB857printed OOInfineon

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

      What it is
      Not recorded
      Maker
      Infineon
      Package
      Not recorded
      Pins
      Not recorded
      Source
      From the manufacturer's datasheet

      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:
      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.

      Datasheetfor BB857, opens in a new tab
    • TPS7A2033DQNprinted QOLDO regulator, 4 pins, Texas Instruments

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

      What it is
      LDO regulator
      Maker
      Texas Instruments
      Package
      Not recorded
      Pins
      4
      Details
      300mA, Ultra-Low-Noise, Low-IQ, High PSRR LDO
      Source
      From the manufacturer's datasheet

      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.

      Datasheetfor TPS7A2033DQN, opens in a new tab
9 more parts have codes that begin with DD

Codes that begin with DD

For a marking with its end worn or burnt off. Each one shows its full printed code.

all Texas Instruments. What differs:

  • LMR16006XDDCprinted D02XDC DC converter, 6 pins

    Printed D02X. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    DC DC converter
    Maker
    Texas Instruments
    Package
    Not recorded
    Pins
    6
    Details
    SIMPLE SWITCHER® 60 V 0.6 A Buck Regulators With High Efficiency ECO Mode
    Source
    From the manufacturer's 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.

    Datasheetfor LMR16006XDDC, opens in a new tab
  • LMR16006YDDCprinted D02YDC DC converter, 6 pins

    Printed D02Y. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    DC DC converter
    Maker
    Texas Instruments
    Package
    Not recorded
    Pins
    6
    Details
    SIMPLE SWITCHER® 60 V 0.6 A Buck Regulators With High Efficiency ECO Mode
    Source
    From the manufacturer's 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.

    Datasheetfor LMR16006YDDC, opens in a new tab
  • TLV70012DDCprinted ODOLDO regulator, 5 pins

    Printed ODO. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    LDO regulator
    Maker
    Texas Instruments
    Package
    Not recorded
    Pins
    5
    Details
    200-mA, Low-IQ, Low-Dropout Regulator for Portable Devices
    Source
    From the manufacturer's datasheet

    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.

    Datasheetfor TLV70012DDC, opens in a new tab
  • TLV70015DDCprinted ODPLDO regulator, 5 pins

    Printed ODP. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    LDO regulator
    Maker
    Texas Instruments
    Package
    Not recorded
    Pins
    5
    Details
    200-mA, Low-IQ, Low-Dropout Regulator for Portable Devices
    Source
    From the manufacturer's datasheet

    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.

    Datasheetfor TLV70015DDC, opens in a new tab
  • TLV70018DDCprinted ODKLDO regulator, 5 pins

    Printed ODK. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    LDO regulator
    Maker
    Texas Instruments
    Package
    Not recorded
    Pins
    5
    Details
    200-mA, Low-IQ, Low-Dropout Regulator for Portable Devices
    Source
    From the manufacturer's datasheet

    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.

    Datasheetfor TLV70018DDC, opens in a new tab
  • TLV70028DDCprinted ODLLDO regulator, 5 pins

    Printed ODL. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    LDO regulator
    Maker
    Texas Instruments
    Package
    Not recorded
    Pins
    5
    Details
    200-mA, Low-IQ, Low-Dropout Regulator for Portable Devices
    Source
    From the manufacturer's datasheet

    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.

    Datasheetfor TLV70028DDC, opens in a new tab
  • TLV70030DDCprinted ODMLDO regulator, 5 pins

    Printed ODM. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    LDO regulator
    Maker
    Texas Instruments
    Package
    Not recorded
    Pins
    5
    Details
    200-mA, Low-IQ, Low-Dropout Regulator for Portable Devices
    Source
    From the manufacturer's datasheet

    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.

    Datasheetfor TLV70030DDC, opens in a new tab
  • TLV70033DDCprinted ODNLDO regulator, 5 pins

    Printed ODN. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    LDO regulator
    Maker
    Texas Instruments
    Package
    Not recorded
    Pins
    5
    Details
    200-mA, Low-IQ, Low-Dropout Regulator for Portable Devices
    Source
    From the manufacturer's datasheet

    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.

    Datasheetfor TLV70033DDC, opens in a new tab
  • TMP20AIDRLprinted ODATemperature sensor, 6 pins

    Printed ODA. Only the start matches what you typed, so this fits only if the rest of the marking is worn off.

    What it is
    Temperature sensor
    Maker
    Texas Instruments
    Package
    Not recorded
    Pins
    6
    Details
    ±2.5°C Low-Power, Analog Out Temperature Sensor
    Source
    From the manufacturer's 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.

    Datasheetfor TMP20AIDRL, opens in a new tab

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 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; 3 a month are free.

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.