How long electrolytic caps last?

Peter Daniel · 25th April 2002, 12:38 AM

I have just removed some electrolytics from my preamp with a thought that I might use them in my SOZ. After I checked them I was quite dissapointed. They measure nothing and don't get charged when I connect them to PS. They've been in a preamp for 7 years and the power was always on. Four caps in parallel, 3,000uF/40V ea. Is that normal? I've heard about caps aging but never observed it first hand. BTW I still have the same caps which I never used and they measure perfectly. The ones that are more yellow are the defective ones.
Thanks for your advice.

jam · 25th April 2002, 02:36 AM

I'd say about 10 -15 years, but with the improvements in capacitor technology you could get a whole lot more capacitance in a smaller space with lower ESR to boot, maybe it is time to replace those cans.

Jam

jam · 25th April 2002, 02:47 AM

I'd say about 10 -15 years, but with the improvements in capacitor technology you could get a whole lot more capacitance in a smaller space with lower ESR to boot, maybe it is time to replace those cans.

Jam

Petter · 25th April 2002, 09:37 AM

1. Technology: Dry electrolytics last "forever"
2. Wet ones: Depends on a) physical size (takes longer to evaporate), temperature exposed to, core temperature, construction of seals.
3. Overloading/loading -- voltage and current.

Caps that are smaller than .75" diameter should not be trusted for more than 10 years unless particularly high quality or if kept at low voltages, or better still low currents.

If they have not been used for a while, you might want to charge them up 10 120% of rating through a resistor so that current is kept low + leave with voltage on for 10-15 minutes. You could use say 100-1000 Ohms, it is not critical, but you probably need a high power unit.

Petter

alvaius · 25th April 2002, 02:53 PM

Electrolytic life is highly dependant on how you use them. The big killer is heat. Heat can come from both external sources and internal sources. If you put those in a power amp that runs hot, that could be an issue. In a low temp pre-amp, that should not be so much of an issue. Internal heating is of course from losses in the cap from in-circuit use. One thing to watch is that you are not exceeding the ripple current. That can drastically shorten the life! If you look at electrolytic data sheets, they generally have a stated life at a given temperature. Reduce the temperature, and that life increases significantly. Not too long ago, most were rated at 85 celsius. Now, some of the better ones are rated at 105 or 125 celsius. That is better in terms of life, you still need to determine how they will behave in your system, though most of the high temp ones are also very low ESR and hence may make a good power supply capacitor.

mrfeedback · 26th April 2002, 03:52 AM

I read somewhere (EW magazine I think) that electrolytes can 'wear out'.
In my servicing work experience, cans mounted on their sides or rubber bung downside last better - maybe the rubber dries and allows leakage.

Regards, Eric.

Peter Daniel · 26th April 2002, 04:34 AM

Jam,
After your advice I decided to use more modern electrolytics in my upcoming SOZ project, however, I'm not totally sure they are better.

peranders · 26th April 2002, 08:05 AM

Surf to ELNA and Philips (BC Components) for nomograms over life expectancy. They are very good but I haven't got the exact URL.

But as a conclusion: Don't use old "used" caps in new projects. Go for brand new. You don't need "Computer grade" types.

mefinnis · 26th April 2002, 11:28 AM

I've had quite a bit of luck with surplus caps, but they definitely have a life.

BTW ..... do you have stocks in aluminium ??????

2nd point ..... don't go overboard with filter caps in SoZ, because of the design it is far less susceptible to rail ripple cf SE designs .... just a hint

As always ..... have fun

cheers, mark

jam · 26th April 2002, 12:33 PM

Peter,

I am sure your new cap bank will sound better. Several audio manufacturers have replaced large electrolytics with many smaller ones. Lower ESR and better high frequency characteristics.
Your new cap bank looks good.

Jam

P.S. You must have a machine shop at home, you have got most of us jealous.

25th April 2002, 09:37 AM	#4
Petter diyAudio Member Join Date: Jan 2001 Location: Scandinavia	There are many factors 1. Technology: Dry electrolytics last "forever" 2. Wet ones: Depends on a) physical size (takes longer to evaporate), temperature exposed to, core temperature, construction of seals. 3. Overloading/loading -- voltage and current. Caps that are smaller than .75" diameter should not be trusted for more than 10 years unless particularly high quality or if kept at low voltages, or better still low currents. If they have not been used for a while, you might want to charge them up 10 120% of rating through a resistor so that current is kept low + leave with voltage on for 10-15 minutes. You could use say 100-1000 Ohms, it is not critical, but you probably need a high power unit. Petter

26th April 2002, 08:05 AM	#8
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Time of life Surf to ELNA and Philips (BC Components) for nomograms over life expectancy. They are very good but I haven't got the exact URL. But as a conclusion: Don't use old "used" caps in new projects. Go for brand new. You don't need "Computer grade" types. __________________ /Per-Anders (my first name) or P-A as my friends call me Tube Buffered Gainclone in work \|Thread

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25th April 2002, 02:36 AM	#2
jam diyAudio Member Join Date: May 2001 Location: Charlotte,NC,USA	I'd say about 10 -15 years, but with the improvements in capacitor technology you could get a whole lot more capacitance in a smaller space with lower ESR to boot, maybe it is time to replace those cans. Jam

25th April 2002, 02:47 AM	#3
jam diyAudio Member Join Date: May 2001 Location: Charlotte,NC,USA	I'd say about 10 -15 years, but with the improvements in capacitor technology you could get a whole lot more capacitance in a smaller space with lower ESR to boot, maybe it is time to replace those cans. Jam

25th April 2002, 02:53 PM	#5
alvaius diyAudio Member Join Date: Feb 2002 Location: Toronto	Electrolytic life is highly dependant on how you use them. The big killer is heat. Heat can come from both external sources and internal sources. If you put those in a power amp that runs hot, that could be an issue. In a low temp pre-amp, that should not be so much of an issue. Internal heating is of course from losses in the cap from in-circuit use. One thing to watch is that you are not exceeding the ripple current. That can drastically shorten the life! If you look at electrolytic data sheets, they generally have a stated life at a given temperature. Reduce the temperature, and that life increases significantly. Not too long ago, most were rated at 85 celsius. Now, some of the better ones are rated at 105 or 125 celsius. That is better in terms of life, you still need to determine how they will behave in your system, though most of the high temp ones are also very low ESR and hence may make a good power supply capacitor.

26th April 2002, 03:52 AM	#6
mrfeedback diyAudio Member Join Date: Feb 2002 Location: Perth, Australia.	I read somewhere (EW magazine I think) that electrolytes can 'wear out'. In my servicing work experience, cans mounted on their sides or rubber bung downside last better - maybe the rubber dries and allows leakage. Regards, Eric.

26th April 2002, 11:28 AM	#9
mefinnis diyAudio Member Join Date: Feb 2001 Location: Adelaide, Australia	I've had quite a bit of luck with surplus caps, but they definitely have a life. BTW ..... do you have stocks in aluminium ?????? 2nd point ..... don't go overboard with filter caps in SoZ, because of the design it is far less susceptible to rail ripple cf SE designs .... just a hint As always ..... have fun cheers, mark

26th April 2002, 12:33 PM	#10
jam diyAudio Member Join Date: May 2001 Location: Charlotte,NC,USA	Peter, I am sure your new cap bank will sound better. Several audio manufacturers have replaced large electrolytics with many smaller ones. Lower ESR and better high frequency characteristics. Your new cap bank looks good. Jam P.S. You must have a machine shop at home, you have got most of us jealous.