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SMD code U01

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.

U01 on a chip capacitor

10 nF

10 nF capacitor

The u is both the decimal point and the unit: 10 nF.

Check it with a meter

Lift one end and measure it on a capacitance range. A good one reads close to 10 nF. In circuit the meter also sees everything connected across it, so the reading means little until it is out. A failed one usually reads near 0 Ω, or a steady low resistance, on the ohms range, often from a crack. On the board a shorted capacitor shorts its whole rail. A failed reading does not change what to fit: the marking still says 10 nF.

On a transistor or diode body (SOT-23-5, DFN, SMC), U01 is a part code instead. Those parts are listed below.

2 parts are printed U01

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.

  • SMTPA62SMB2 pins, SGS-Thomson MicroelectronicsNot recordedSMB2 pinsSGS-Thomson Microelectronics
    What it is
    Not recorded
    Maker
    SGS-Thomson Microelectronics
    Package
    SMB
    Pins
    2
    Details
    TVS: 62V, 50A(1ms), 5W, Bidirectional
    Source
    Published code list

    Is it dead? The meter test is below: TVS or ESD protection diode.

  • 1 more part has no package on record
    • US5U1N-channel MOSFET, ROHMN-channel MOSFETNot recordedNot recordedROHM
      What it is
      N-channel MOSFET
      Maker
      ROHM
      Package
      Not recorded
      Pins
      Not recorded
      Details
      N-Channel MOSFET + Schottky Barrier Diode
      Source
      Published code list

      Is it dead? The meter test is below: N-channel MOSFET.

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.

N-channel MOSFET

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

Working, it reads

Red probe on the source, black on the drain: about 0.4 to 0.9 V, the body diode. Open the other way. The gate reads open to both other pins, both ways.

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. Often all three pins end up shorted together.
  • No body diode at all: failed open.
On the board
the gate usually has a resistor to the source, so gate to source reads that resistor, which is not a fault. A drain short can be the load. 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.

Printed with a code easy to misread as U01

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 U01

For a marking with its end worn or burnt off. Each code has a page of its own.

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