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SMD code LF

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.

2 parts are printed LF

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.

  • PESD36VS2UTSOT-23ESD protection diode, 3 pins, Nexperia
    What it is
    ESD protection diode
    Maker
    Nexperia
    Package
    SOT-23
    Pins
    3
    Details
    Low capacitance unidirectional double ESD protection diode
    Source
    From the manufacturer's datasheet

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

    Datasheetfor PESD36VS2UT, opens in a new tab
  • 1 more part has no package on record
    • BAL99TBSwitching diode, Panjit
      What it is
      Switching diode
      Maker
      Panjit
      Package
      Not recorded
      Pins
      Not recorded
      Source
      From the manufacturer's datasheet

      Is it dead? The meter test is below: Silicon diode.

      Datasheetfor BAL99TB, opens in a new tab

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.

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.

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.

Printed with a code easy to misread as LF

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 LF

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

Codes not listed here are printed on 21 more parts.

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