30 May
2007
30 May
'07
3:45 p.m.
It's neither electrolytic or 22uF (seemingly, the
European comma decimal point
is confusing the writer), and it didn't fail by 'drying out' as the writer
writes. It's 0.22 uF and (probably) mylar or polystyrene, and a replacement
should be 'line-rated' as it's somewhat obviously part of the line filter.
The
I nte UK (and m,aybe elsewhere) thera are 2 types of mains-rated
capacitors, called 'Class X' and 'Class Y'
Class X capacitors are rated to stand mains, and are intended to be
connected between live and neutral
Class Y are also rated to stand mains, but are also designed not to be
able to fail short-circuit. They're connected between either side of the
mains and protective ground (we call it 'earth'). Even if the earth wire
fails, the casing still cna't become live due to a fault in the capacitor.
Class Y are (not suprisingly) more expensive than class X, and tend to be
made in smaller values only. A typical mains filter stage might have a
0.1uF Class X between live and neutral, and a pair of 4.7nF Class Y
capacitors, one from live to earth, the other from neutrol to earth.
In this case, i would guess the 0.22uF is a Class X (I've never sene a
capacitor to earht that large i na mains filter).
Maybe it's the climate around here (mild) but
other than early tube equipment
and the occassional leaking one (and the well-known manufacturing problems in
the mid/late-90's), I don't often have problems from electrolytics; or to put
it another way, I'm of the feeling the concern over electrolytics is overstated.
To put it more concisely perhaps, I think the well-justified
concern/experience with early 'lytics has carried too far over to more modern
equipment/components.
I would agree. I've changed a few electrolytics in classic computer
equipment, but iut's certainly not a common failure problem.
-tony