"mm" wrote in message
...
On Tue, 20 Feb 2007 15:55:10 +1100, Franc Zabkar
wrote:

On Mon, 19 Feb 2007 19:55:37 -0500, mm put
finger to keyboard and composed:

I have to replace a small capacitor that had a lead ripped out when
the tv was dropped and the pcb broken.

It's a cylinder about a half inch high, a quarter inch in diameter,
with two leads at the bottom, and a narrowing near the bottom, like a
waist line, but it gets back to full diameter at the bottom.

It's black and says on it:

extra info
TL [in an elongated circle]
50v4.7uF --

CD71
40/085/10
N --

All my Googling suggests that "CD71" is a bipolar or non-polarised
aluminium electrolytic. Yours seems to be a standard temperature type,
ie -40C to +85C. The "10" may refer to the tolerance.

Thanks. I didnt' realize CD71 would be the part number.

Since I need 4.7uF, I have two polarised 50v 2.2uF caps of the same
appearance as the one I need to replace, that I was going to connect
in parallel, with the negatives connected together.

If instead I connected them in parallel with each negative connected
to the other's positive, would that give me the equivalent of a
non-polarised cap?


To "make" a non polarised electrolytic, you have to connect two
electrolytics of twice the required value - in your case that would be 10uF
each - in inverse series. Usually, you connect the two ' - ' legs together
leaving the two ' + ' legs to go to the outside world. Each cap need only be
half the working voltage of the original non-polarised in theory, but it's
not a bad idea to make each one the same as the original as, depending on
what exactly is across the cap, you can't guarantee that the voltage will
divide equally between them. However, all that said, non-polarised caps are
readily available, so unless you are really stuck for obtaining one, it's
better to fit what was originally there.

Arfa
- Franc Zabkar


If you are inclined to email me
for some reason, remove NOPSAM :-)