SMD code 304H
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.
304H on a chip capacitor
300 nF, 50 V
300 nF, 50 V tantalum capacitor
A moulded tantalum capacitor: 304 is the capacitance in picofarads (300 nF) and H is the rated-voltage code (50 V). Makers disagree on the letter for 50 V: T at Kyocera AVX and Vishay, H at ROHM.
Check it with a meter
Lift one end and measure it on a capacitance range. A good one reads close to 300 nF. In circuit the meter also sees everything connected across it, so the reading means little until it is out. It is polarised: the band on the body marks the positive end, and a tantalum fitted backwards fails short, sometimes with a flame. A failed tantalum usually reads near 0 Ω both ways, often with a burnt or cracked body. A failed reading does not change what to fit: the marking still says 300 nF, 50 V. Fit the same capacitance at the same or a higher voltage.
On a transistor or diode body (SMA), 304H is a part code instead. Those parts are listed below.
The only part printed 304H in our tables
SZ304H
- What it is
- Zener diode
- Maker
- EIC Semiconductor
- Package
- SMA
- Pins
- 2
- Details
- Zener diode: 4.7V±10%, Izt=79.8mA, Zzt=5.0, 1.5W
- Source
- Published code list
Is it dead?
Diode range for the forward check, part lifted, red probe on the anode. A bench supply for the Zener voltage.
Working, it reads
About 0.6 to 0.8 V forward and open in reverse on the diode range. Its Zener voltage shows only on a supply: feed it through a resistor that sets about 5 mA, cathode to positive, read quickly, and it should hold near its rated voltage.
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, forward too: failed open.
- Holds well off its rated voltage on the supply test: drifted.
- A soft knee, or a voltage that creeps on the supply test: 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 meter's diode range stops at about 2 to 3 V, so almost every Zener reads open in reverse on it, good or bad; a 3 V meter may just show a 2.4 or 2.7 V part. Above about 3 V the meter cannot tell a Zener from a plain diode.
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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