chizad1980

I was reading a thread a while back and someone said that capacitors have an expiration date. Is this true. I don't believe mine has one, but I really havent taken a good look at it. Mine is from 1998 and has been constantly been used on at least 2 amps sometimes 3. Do I need to get a new one?

apitat

Also, is there any way to test the cap to see if it's losing power, etc?

mattrush78

Capacitors don't have expiration dates. Most good amps have capacitors for power storage. If they had expiration dates we would have to buy new amps every couple of years.

I don't know of any way to test capacitors. I would like to know if someone knows how to test them. It would be cool to know!!

chizad1980

Wonder why someone said this? Maybe they don't know what they are talking about. By the way, I was talking about the huge caps that you have prioir to the amps, like 1 farad and stuff. But either way a cap is a cap. Regarding how to test them, I've got a fairly good Digital Multimeter, it's a Wavetek I think, like $140. It's got 2 slots that you put the terminals of the capacitors into and it will read the capacitance. I'm not sure the max it will read, but I'm pretty sure it won't read a 1 farad cap.

hinrgdj

Heat is a capacitor's worst enemy...the actual value/tolerance could be +50%, -20% of the value marked. The important factors to measure would be the ESR (equivalent series resistance), DA (dielectric absorption), and leakage. This would take a lab instrument, not a multimeter.

dajuice27

I'll check and see what equipment we have here in the engineering shop. I'll ask around on a method to check incoming and outgoing resistance levels in the cap, especially since I just bought one for my system.

Good question by the way, never thought of that.

Akim711

hook it up to an oscilloscope with a small resistance in parallel.

RhoXS

I strongly suspect that the big filter capacitor you are talking about is an "electrolytic capacitor." If you open one up (don't) you will find, among other stuff, a wet paste. This is the "electrolyte." After time, these capacitors have a tendency to leak or dry out. Leaks are obvious because of the obviously corrosive white percipitate that appears around the seals. Drying out is not so obvious but also kills it. More frequently than not, these problems are what causes your household electrinic equipment (e.g. camcorders, etc) to die or operate poorly after five to ten years.

There is no expiration date that I know of but heat will definetly shorten their life expectancy as hinrgdj previously said.

Huge capacitors like you are referring to act as a big buffers to filter out equipment damaging and noise causing voltage spikes and transients. They also act as a big energy resevoir if your audio equipment is momentarily asking for more power than your electrical system can provide. If there is no obvious damage to it and your audio equipment is performing as you expect, don't worry about it.

chizad1980

Very informative RhoXS. I believe they are electrolytic. It has been in the trunk in very hot and cold temps for 4 years, but I don't see anything coming out of it. I was just wondering if there were any bottlenecks in my system. Thanks