SMD code K0391
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.
K0391 on a chip resistor
39.1 Ω
39.1 Ω resistor
The K is both the decimal point and the multiplier: 39.1 Ω.
Check it with a meter
Lift one end and measure across it. A good one reads 39.1 Ω. Measuring it in circuit reads the parallel combination of everything around it, which is almost always lower, never higher: well above 39.1 Ω on the board is a fault. Open, or well above 39.1 Ω, means it has failed: burnt, cracked or corroded. That does not change what to fit: the marking still says 39.1 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, K0391 is a part code instead. Those parts are listed below.
The only part printed K0391 in our tables
RJK0391DPA
- What it is
- Not recorded
- Maker
- Renesas
- Package
- Not recorded
- Pins
- Not recorded
- Details
- N Channel Power MOSFET
- Source
- Published code list
Is it dead?
Diode range, part lifted. Test drain to source first, then short gate to source and test again.
Working, it reads
One way between drain and source reads about 0.4 to 0.9 V, the body diode, and the other way open. The gate reads open to both other pins.
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.
- No body diode at all: failed open.
- On the board
- the gate usually has a resistor to the source, which reads as that resistor and is not a fault. 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.
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