SMD code K121
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.
K121 on a chip resistor
121 Ω
121 Ω resistor
The K is both the decimal point and the multiplier: 121 Ω.
Check it with a meter
Lift one end and measure across it. A good one reads 121 Ω. Measuring it in circuit reads the parallel combination of everything around it, which is almost always lower, never higher: well above 121 Ω on the board is a fault. Open, or well above 121 Ω, means it has failed: burnt, cracked or corroded. That does not change what to fit: the marking still says 121 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-23-5), K121 is a part code instead. Those parts are listed below.
The only part printed K121 in our tables
TS971IYLT
- What it is
- Not recorded
- Maker
- STMicroelectronics
- Package
- SOT-23-5
- Pins
- 5
- Source
- Published code list
Is it dead?
Diode range and ohms range, part lifted.
Working, it reads
Depends on what it is. The datasheet, or an identical part, says.
Dead, it reads
- Between two pins, the same reading both ways, near 0 V with a continuous beep: shorted.
- Open between every pair of pins: failed open, or a part that reads open when working.
- 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.
A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.
Was it this one?
Did you find your part?
Open this in the search to correct a character or try another package.