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SMD marking

R1in SOT-363

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.

R1 on a chip resistor

0.1 Ω

0.1 Ω resistor

The R stands in for the decimal point, which is how sub-ohm and fractional values are printed.

Check it with a meter

Lift one end and measure across it. A good one reads 0.1 Ω. Measuring it in circuit reads the parallel combination of everything around it, which is almost always lower, never higher: well above 0.1 Ω on the board is a fault. Open, or well above 0.1 Ω, means it has failed: burnt, cracked or corroded. That does not change what to fit: the marking still says 0.1 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, SOT-353, SMA), R1 is a part code instead. Those parts are listed below.

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.

The only part printed R1 in this package in our tables

PUMF11

What it is
Digital transistor (NPN, resistors built in)
Maker
Nexperia
Package
SOT-363
Pins
6
Details
NPN resistor-equipped transistor;
Source
From the manufacturer's datasheet

Is it dead?

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:
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.

Datasheetfor PUMF11, opens in a new tab

Printed with a code easy to misread

This part is printed with a character that is easy to misread as what you typed. The odd one out is marked on each.

  • BFP196printed RIRF transistor, Infineon

    Printed RI on the part. Easy to misread as R1. Check that character with a loupe before you order anything.

    What it is
    RF transistor
    Maker
    Infineon
    Package
    Not recorded
    Pins
    Not recorded
    Source
    From the manufacturer's datasheet

    Is it dead?

    Diode range, part lifted or its base leg off the pad.

    Working, it reads

    From the base, one probe colour reads about 0.6 to 0.75 V to the emitter and to the collector, and open the other way round. Collector to emitter reads open both ways.

    Dead, it reads

    • Collector to emitter the same both ways, near 0 V with a continuous beep: shorted. The commonest failure.
    • The base the same both ways to another pin, near 0 V or a middling value: a shorted junction.
    • Only one junction reads, or none: a junction has failed open. It then looks like a diode.
    • A reading the wrong way round, where it should be open: leaky.
    On the board:
    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 pair of diodes with a common pin reads just like a transistor, and some transistors carry a built-in diode or resistor. The datasheet says which.

    A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

    Datasheetfor BFP196, opens in a new tab

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