On Feb 28, 11:35*am, tommi wrote:
On Sat *28Feb 15:08, att wrote



"tommi" wrote:

Can you help me ID a small capacitor. The photo shows two
identical capacitors which are marked with: * 225F *
Underneath that marking is a + sign followed by a long line.

http://i39.tinypic.com/2kn8u0.jpgshowing AA battery holder.

(1) Are they likely to be tantalum capacitors?

(2) Does that marking mean they are 220nF or are they 220pF? *Or
some other value?

2.2uf, voltage unknown. *They sure look like tantalums.

I've heard tantalum capacitors can get noisy or break down over time.

The device in my photo is used to power a microphone. So any noise
from it would be very unwelcome. *

Is it worth changing those capacitors to another type? *Would
something like a polyester capacitor have enough capacity for 2.2uF
and still be physically small enough to fit in the space on the
circuit board shown in my photo?

http://i39.tinypic.com/2kn8u0.jpg

--
nb:groups widened

I've used tantalums (SMT version, but built basically the same
internal construction as what shows in your picture) in an application
where I rely on them being very quiet. The caps I use are operated at
a fairly small fraction of their rated working voltage. The circuit
has been in production for years, and I've never heard of a problem.
Tantalums absolutely CAN have problems with noise, and I've run tests
that show it readily, but my experience is that they are quiet between
noise pulses and the noise pulses occur very seldom indeed if you
operate at no more than, say, 1/3 the rated voltage.

Cheers,
Tom