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SMD code 72S

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.

72S on a chip resistor

54.9 Ω

54.9 Ω resistor, 1%

EIA-96 precision code: 72 selects 5.49 from the E96 series and S multiplies by 10. These are 1% parts. The trailing S is also used as a decimal point, so this could instead be 72 Ω. Measure it before fitting a replacement. If it has failed and reads open or high, that settles nothing: measure the same position on a working board.

Check it with a meter

Lift one end and measure across it. A good one reads 54.9 Ω within 1%. Measuring it in circuit reads the parallel combination of everything around it, which is almost always lower, never higher: well above 54.9 Ω on the board is a fault. Open, or well above 54.9 Ω, means it has failed: burnt, cracked or corroded. That does not change what to fit: the marking still says 54.9 Ω. A burnt resistor usually means the part it feeds drew too much, so find that before fitting a new one.

On a transistor or diode body (SOT-23, TO-220), 72S is a part code instead. Those parts are listed below.

2 parts are printed 72S

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.

  • BAT721SSOT-23Schottky diode, Panjit
    What it is
    Schottky diode
    Maker
    Panjit
    Package
    SOT-23
    Pins
    3
    Source
    From the manufacturer's datasheet

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

    Datasheetfor BAT721S, opens in a new tab
  • 1 more part has no package on record
    • 2N7002N-channel MOSFET, Infineon
      What it is
      N-channel MOSFET
      Maker
      Infineon
      Package
      Not recorded
      Pins
      Not recorded
      Details
      N-channel enhancement mode Field-Effect Transistor (FET), 60V, SOT-23
      Source
      From the manufacturer's datasheet

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

      Datasheetfor 2N7002, 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.

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.

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.

Codes that begin with 72S

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

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