steamer said:
--Silly question time: do capacitors tend to drift in the same
direction? And if so, which way? Just got stereo out of the shop and the
repair guy said the problem was with the caps..
Capacitors can fail. They lose their capacitance over time and electrolytic
can drop significantly. This is probably what you are asking for as it makes
the most sense. Capacitance can obvious locally change due to temperature
fulgurations and other things but generally it will not cause a circuit to
fail or generally even operate erratically(unless it is very poorly
designed). But if it is old or uses cheap capacitors, specifically if
electrolytics, then the device can fail in any number of ways.
For audio stuff caps tend to be used for two primary purposes. One is power
regulation and the other is audio filtering. The filtering caps generally
rarely go bad and if they do it is results in a gradual decay of sound
quality except when a catastrophic event occurs. The power regulation caps
are generally what fail the most and can be due to over voltages and such.
They are the large capacitors in the device. Generally they cost up to a few
bucks each so if he charged you an arm and a leg then he's probably ripping
you off. For example, it could simply have been a fuse and he said it was
the caps.
If they were replaced it should be someone easy to tell and generally there
are just two to four of these(they will be the largest ones there). It is
possible the power stage uses SMPS which reduces cap size and may make it
harder to find the.
BTW, a capacitor is basically a battery that works in a similar way but has
opposite properties. A capacitor can be charged up or discharged very
quickly(battery = slowly) and cannot old a charge as long(a battery can last
quite some time). In fact, in some cases capacitors can be used to replace
batteries(so called supercaps that can hold a ton of charge). Actually a
battery is a type of capacitor that was designed to last longer but at the
price of not being able to dump it's electrons as quick.
Example, if you short out a capacitor it will "release" a large number of
electrons in almost an instant. Say maybe something like 1 million amps in
1ps(10^-9 seconds). 5ps later it maybe down to 10,000A. 1000ps later it's
basically at 0.
A batter OTH might be able to put out a few amps for several minutes which
will slowly drop off.
Of course I'm just trying to give you some idea as the specific numbers
depend on the actual devices used.
