SMD code 55-
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.
105 parts are printed 55-
Not sure which one you have?
Answer up to 4 quick questions and these 50 parts are ranked, with a meter test that settles it. It works on a dead part too.
BAT17-05SOT-23Schottky diode, 3 pins, InfineonSchottky diodeSOT-233 pinsInfineon
- What it is
- Schottky diode
- Maker
- Infineon
- Package
- SOT-23
- Pins
- 3
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
BZT52B3V9LSOD-882Zener diode, 2 pins, Galaxy MicroelectronicsZener diodeSOD-8822 pinsGalaxy Microelectronics
- What it is
- Zener diode
- Maker
- Galaxy Microelectronics
- Package
- SOD-882
- Pins
- 2
- Details
- 3.9V, 100mW, Surface Mount Zener Diodes
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
BZX84-A3V9SOT-23Zener diode, 3 pins, NexperiaZener diodeSOT-233 pinsNexperia
- What it is
- Zener diode
- Maker
- Nexperia
- Package
- SOT-23
- Pins
- 3
- Pinout
- 1 anode
- 2 not connected
- 3 cathode
- Details
- 3.9 V ±1% voltage regulator (Zener) diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
BZX584B3V9SOD-523Zener diode, 2 pins, Galaxy MicroelectronicsZener diodeSOD-5232 pinsGalaxy Microelectronics
- What it is
- Zener diode
- Maker
- Galaxy Microelectronics
- Package
- SOD-523
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
BZX584C3V9SOD-523Zener diode, 2 pins, Yangjie Electronic TechZener diodeSOD-5232 pinsYangjie Electronic Tech
- What it is
- Zener diode
- Maker
- Yangjie Electronic Tech
- Package
- SOD-523
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
BZX584C3V9QSOD-523Zener diode, 2 pins, Yangjie Electronic TechZener diodeSOD-5232 pinsYangjie Electronic Tech
- What it is
- Zener diode
- Maker
- Yangjie Electronic Tech
- Package
- SOD-523
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
BZX584C20SOD-523Zener diode, 2 pins, Formosa MicrosemiZener diodeSOD-5232 pinsFormosa Microsemi
- What it is
- Zener diode
- Maker
- Formosa Microsemi
- Package
- SOD-523
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
BZX584C22SOD-523Zener diode, 2 pins, Formosa MicrosemiZener diodeSOD-5232 pinsFormosa Microsemi
- What it is
- Zener diode
- Maker
- Formosa Microsemi
- Package
- SOD-523
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
DTA023EEBSOT-416Digital transistor (PNP, resistors built in), 3 pins, ROHMDigital transistor (PNP, resistors built in)SOT-4163 pinsROHM
- What it is
- Digital transistor (PNP, resistors built in)
- Maker
- ROHM
- Package
- SOT-416
- Pins
- 3
- Details
- PNP -100mA -50V Digital Transistor (Bias Resistor Built-in Transistor)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
DTA023EMSOT-723Digital transistor (PNP, resistors built in), 3 pins, ROHMDigital transistor (PNP, resistors built in)SOT-7233 pinsROHM
- What it is
- Digital transistor (PNP, resistors built in)
- Maker
- ROHM
- Package
- SOT-723
- Pins
- 3
- Details
- PNP -100mA -50V Digital Transistor (Bias Resistor Built-in Transistor)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
DTA023EUBSOT-323Digital transistor (PNP, resistors built in), 3 pins, ROHMDigital transistor (PNP, resistors built in)SOT-3233 pinsROHM
- What it is
- Digital transistor (PNP, resistors built in)
- Maker
- ROHM
- Package
- SOT-323
- Pins
- 3
- Details
- PNP -100mA -50V Digital Transistor (Bias Resistor Built-in Transistor)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
EDZV16BSOD-523Zener diode, 2 pins, ROHMZener diodeSOD-5232 pinsROHM
- What it is
- Zener diode
- Maker
- ROHM
- Package
- SOD-523
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
3 more parts have no package on record
BBY57-02LInfineonNot recordedNot recordedNot recordedInfineon
- What it is
- Not recorded
- Maker
- Infineon
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: This part.
BZX584B20Zener diode, Formosa MicrosemiZener diodeNot recordedNot recordedFormosa Microsemi
- What it is
- Zener diode
- Maker
- Formosa Microsemi
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
BZX584B22Zener diode, Formosa MicrosemiZener diodeNot recordedNot recordedFormosa Microsemi
- What it is
- Zener diode
- Maker
- Formosa Microsemi
- Package
- Not recorded
- Pins
- Not recorded
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
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.
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.
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.
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.
Digital transistor
Ohms range, part lifted. The datasheet gives the built-in resistors: R1 in series with the base, R2 from base to emitter.
Working, it reads
Base to emitter reads about R1 plus R2 either way round, about 20 kΩ on a 10 k and 10 k part, give or take their wide tolerance. Collector to emitter reads open. A part with no R2 reads a junction behind R1 one way instead.
Dead, it reads
- Collector to emitter the same both ways, near 0 Ω with a continuous beep: shorted.
- From the base, open or far above R1 plus R2: R1 has failed. Static damage shows here most often.
- Base to emitter near 0 Ω: failed short.
- 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:
- The readings depend on the resistor values, so an identical part elsewhere on the board is the surest reference. Measure it the same way.
- Watch for:
- On the diode range a good part with 10 kΩ resistors reads open on every pair, so a good part looks dead there. Use the ohms range.
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 55-
One character differs, and it is one that is easy to confuse under a lamp. Each code has a page of its own.
Codes not listed here are printed on 6 more parts.
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