SMD code S55 in SOT-323
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.
1 part in SOT-323 is printed S55
Not sure which one you have?
Answer up to 4 quick questions and these 3 parts are ranked, with a meter test that settles it. It works on a dead part too.
FJX4005RSOT-323Digital transistor (PNP, resistors built in), 3 pins, Fairchild SemiconductorDigital transistor (PNP, resistors built in)3 pinsFairchild Semiconductor
- What it is
- Digital transistor (PNP, resistors built in)
- Maker
- Fairchild Semiconductor
- Package
- SOT-323
- Pins
- 3
- Details
- PNP transistor: Sw, 50V, 100mA, 200mW, R1/R2=4.7k/10k
- Source
- Published code list
Is it dead? The meter test is below: Digital transistor.
2 more parts have no package on record. Nothing rules them out, so they stay.
SS55Schottky diode, Taitron ComponentsSchottky diodeNot recordedTaitron Components
- What it is
- Schottky diode
- Maker
- Taitron Components
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Surface Mount Schottky Rectifiers
- Source
- Manufacturer datasheet
Is it dead? The meter test is below: Schottky diode.
SS5P5Schottky diode, VishaySchottky diodeNot recordedVishay
- What it is
- Schottky diode
- Maker
- Vishay
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Diode: SBR, 50V, 5A, Vf<0.69V(5A)
- Source
- Published code list
Is it dead? The meter test is below: Schottky 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.
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.
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.
Printed with a code easy to misread as S55
One character differs, and it is one that is easy to confuse under a lamp. Each code has a page of its own.
Codes that begin with S55
For a marking with its end worn or burnt off. Each code has a page of its own.
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