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SMD code 4UF

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.

4UF is a capacitor marking

4 µF

4 µF capacitor

The value is printed in full: 4 µF. A value this large is usually an electrolytic, which is polarised: on an aluminium can the stripe marks the negative lead, and one fitted backwards can vent.

Check it with a meter

Lift one end and measure it on a capacitance range. A good one reads close to 4 µF. In circuit the meter also sees everything connected across it, so the reading means little until it is out. An electrolytic that has dried out can still read close to its value while its ESR has risen, which only an ESR meter shows. A domed or leaking top means it has failed. A failed reading does not change what to fit: the marking still says 4 µF.

On a transistor or diode body (SOT-23-5), 4UF is a part code instead. Those parts are listed below.

3 parts are printed 4UF

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.

  • XC6105F616MRSOT-23-5Voltage supervisor, TorexVoltage supervisorTorex
    What it is
    Voltage supervisor
    Maker
    Torex
    Package
    SOT-23-5
    Pins
    5
    Details
    CMOS-IC: VDet 1.6V, 5%, Hst, +Rst PPO, -Rst ODO, Wt=1.6s, Rt=400ms
    Source
    Published code list

    Is it dead? The meter test is below: Integrated circuit.

  • XC6105F646MRSOT-23-5Voltage supervisor, TorexVoltage supervisorTorex
    What it is
    Voltage supervisor
    Maker
    Torex
    Package
    SOT-23-5
    Pins
    5
    Details
    CMOS-IC: VDet 4.6V, 5%, Hst, +Rst PPO, -Rst ODO, Wt=1.6s, Rt=400ms
    Source
    Published code list

    Is it dead? The meter test is below: Integrated circuit.

  • 1 more part has no package on record
    • SMM4F12ATVS diode, SGS-Thomson MicroelectronicsTVS diodeSGS-Thomson Microelectronics
      What it is
      TVS diode
      Maker
      SGS-Thomson Microelectronics
      Package
      Not recorded
      Pins
      Not recorded
      Details
      Transient voltage supressor: Vrwm=12V, Vbr=13.3..14.7V, Ipp=91A, 400W(1ms)
      Source
      Published code list

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

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.

Integrated circuit

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.

Did you find your part?

Open this in the search to correct a character or try another package.