SMD code 51-
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.
102 parts are printed 51-
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.
1.5SMC51SMCTVS diode, 2 pins, HottechTVS diodeSMC2 pinsHottech
- What it is
- TVS diode
- Maker
- Hottech
- Package
- SMC
- Pins
- 2
- Details
- TVS diode, VRWM 41.3 V, unidirectional
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
3.0SMC51SMCTVS diode, 2 pins, YFWTVS diodeSMC2 pinsYFW
- What it is
- TVS diode
- Maker
- YFW
- Package
- SMC
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: TVS or ESD protection diode.
BZX84-A2V7SOT-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
- 2.7 V ±1% voltage regulator (Zener) diode
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
BZX584C2V7SOD-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.
BZX584C2V7QSOD-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.
DTA015TEBSOT-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 Transistors (Bias Resistor Built-in Transistors)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
DTA015TMSOT-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 Transistors (Bias Resistor Built-in Transistors)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
DTA015TUBSOT-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 Transistors (Bias Resistor Built-in Transistors)
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Digital transistor.
GALI-51+SOT-89RF amplifier (MMIC), 3 pins, Mini-CircuitsRF amplifier (MMIC)SOT-893 pinsMini-Circuits
- What it is
- RF amplifier (MMIC)
- Maker
- Mini-Circuits
- Package
- SOT-89
- Pins
- 3
- Details
- MMIC amplifier, DC-4 GHz
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: RF amplifier.
KDZ5.1EVSOD-523Zener diode, 2 pins, KECZener diodeSOD-5232 pinsKEC
- What it is
- Zener diode
- Maker
- KEC
- Package
- SOD-523
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
KDZ5.1VSOD-323Zener diode, 2 pins, KECZener diodeSOD-3232 pinsKEC
- What it is
- Zener diode
- Maker
- KEC
- Package
- SOD-323
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
LBAV170LT1GSOT-23Switching diode, 3 pins, LRCSwitching diodeSOT-233 pinsLRC
- What it is
- Switching diode
- Maker
- LRC
- Package
- SOT-23
- Pins
- 3
- Details
- Switching diode, VR 85 V, IF 215 mA, VF Max 1 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
LBAV170WT1GSOT-323Switching diode, 3 pins, LRCSwitching diodeSOT-3233 pinsLRC
- What it is
- Switching diode
- Maker
- LRC
- Package
- SOT-323
- Pins
- 3
- Details
- Switching diode, VR 85 V, IF 215 mA, VF Max 1 V
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Silicon diode.
MM3Z51VCWSOD-323Zener diode, 2 pins, Yangjie Electronic TechZener diodeSOD-3232 pinsYangjie Electronic Tech
- What it is
- Zener diode
- Maker
- Yangjie Electronic Tech
- Package
- SOD-323
- Pins
- 2
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Zener diode.
1 more part has no package on record
ERA-51SM+RF amplifier (MMIC), Mini-CircuitsRF amplifier (MMIC)Not recordedNot recordedMini-Circuits
- What it is
- RF amplifier (MMIC)
- Maker
- Mini-Circuits
- Package
- Not recorded
- Pins
- Not recorded
- Details
- MMIC amplifier, DC-4 GHz
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: RF amplifier.
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.
TVS or ESD protection diode
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
- , 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.
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.
RF amplifier
Voltage, board powered, on the output pin that the bias resistor or choke feeds.
Working, it reads
The output pin sits at the device voltage the datasheet gives, a few volts, below the supply.
Dead, it reads
- Output pin at 0 V, or near 0 Ω to ground with the power off: shorted inside.
- Output pin at the full supply voltage: open inside, no current flowing.
- On the board:
- Measured on the board with power on; the bias network is part of the reading.
- 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 figures depend on the part and its bias resistor. The datasheet gives both.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
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.
Printed with a code easy to misread as 51-
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 40 more parts.
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