Reading capacitance on SM capacitor

They probalby exist, but I've never seen a 220pF cap with a polarity marking. For their size, I'd bet on 220uF. I wouldn't count on your resistance measurement meaning bad caps.

mike

Those are 220 uF, probably tantalum. The ordinary failure mode is a short circuit in which case you would read much less than 50 Ohms. Some other part of the circuit is responsible for the 50 Ohm reading.

I tend to think that's 220uF as well, but all the references I've read so far on-line indicate that the number refer to pico Fara, with the last digit indicate the number of zero's to follow... That would make this 22 pF, which is against any other indicators (polarity sign is not popular for small cap, physical size of the cap...) Unless I'm still missing other way to read capacitor from a specific manufaturer.

I know measuring resistance in circuit is not conclusive; but before taking the cap out, I need the replacement ready just in case, therefore I need to read the capacitance value ...

Any other hint ? Thanks for the opinion so far.

First, the largest problems with leaking capacitors were with electrolytics, these are usually large capacitors and are usually not surface mounted.

Testing a capacitor with a voltmeter (ohm-meter) the way that you did won't tell you much and can destroy the item (the laptop). What you measured was mostly the resistance not of the capacitor, but of the REST of the circuit, and in measuring it you applied voltage to it, possibly in the wrong polarity. That can destroy the circuit. If you are going to test a capacitor, you need some specialized equipment and/or you need to test it "out of circuit".

From your size descriptions, I'd guess that they are tantalum rather than electrolytic, thus could not leak (no electrolyte). But they could still be bad, of course. "220", if it's the capacitance at all, most likely means 22 x 10**0 or 22; 220pf is a tiny, very small capacitor, do you perhaps mean 22 MF (there is only a difference there of

nospam_needed wrote:

When you see a 3-digit number on a part (resistor or capacitor), IF the number is the "value" of the part at all (and often it's not), the usual format is that the first two digits are the two significant digit and the 3rd is the power of tens exponent. For example, to take a resistor:

etc.

Both resistors and caps come with only a few "first two significant digits", most commonly:

Frank346 wrote: