SMD code P521
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.
P521 on a chip capacitor
0.52 pF
0.52 pF capacitor
The p is both the decimal point and the unit: 0.52 pF.
Check it with a meter
Lift one end and measure it on a capacitance range. A good one reads close to 0.52 pF. In circuit the meter also sees everything connected across it, so the reading means little until it is out. A failed one usually reads near 0 Ω, or a steady low resistance, on the ohms range, often from a crack. On the board a shorted capacitor shorts its whole rail. A failed reading does not change what to fit: the marking still says 0.52 pF.
On a transistor or diode body, P521 is a part code instead. Those parts are listed below.
The only part printed P521 in our tables
TLP521-1
- What it is
- Not recorded
- Maker
- Toshiba
- Package
- Not recorded
- Pins
- Not recorded
- Details
- Photocoupler GaAs IRED & Photo-Transistor
- Source
- Published code list
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
- 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.
Was it this one?
Codes that begin with P521
For a marking with its end worn or burnt off. Each code has a page of its own.
Did you find your part?
Open this in the search to correct a character or try another package.