Reliability of electrolytics

[Freddybaby]

I have several devices in the field that I had to use electrolytic caps. This is an outdoor application (in Iowa), fairly high reliability in that if it fails it will cause a more expensive device to fail.

My question/comment: The MFG ratings for life are between 1000-4000 hrs. This seems unreasonable or extremely conservative given I have 20yr old equipment that has not failed with this type of cap.

There is a small transformer in the box that should keep out the bitter Iowa cold but I guess this could also lead to problems in the summer such as drying out of the electrolyte.

Am I being paranoid or do I need to buy really expensive military rated caps ?

 

[Audioguru]

American, European and Japanese electrolytic capacitors are reliable. Chinese ones and ones that are made in a country that you never heard about are not.

 

[flatulent]

The three main factors in electrolyte failures are:

1. temperature

2. ripple current

3. applied voltage. maximum reliability is an applied voltage of 80% of the rated voltage. Higher and lower makes for early failures.

 

[atferrari]

The three main factors in electrolyte failures are:

1. temperature

2. ripple current

3. applied voltage.

Not also age?

 

[Audioguru]

In the 60's electrolytic capacitors had rubber seals that dried then cracked. Now they use synthetic neoprene that lasts almost forever.

 

[flatulent]

The three main factors in electrolyte failures are:

1. temperature

2. ripple current

3. applied voltage.

Not also age?

As stated in the above response, the seals are better these days and so the electrolyte does not leak out as much with age.

I have a 25 year old AM FM tuner that I rarely use. It still works and probably contains electrolyte capacitors, especially in the power supply.

 

[Audioguru]

My Scott FM receiver is 46 years old and still works perfectly. It has many original electrolytic capacitors.

It was the first FM receiver to use ICs in its IF amplifier.

 

[vfone]

Years ago I owned a Scott 342 otherwise in beautiful shape, but where I had to replace all the electrolytic capacitors greater than 100uF. And this was not only my problem. I found a lot of people complained about this.
Only starting with '80s manufacturers starts making very reliable electrolytics.

 

[Audioguru]

Mine is a Scott 341. I replaced the FET tone control circuit with low noise, low distortion opamps.

 

[Kral]

Freddybaby
The definition of "lifetime" varies among manufacturesrs. However, a failure is not necessarily a catastrophic failure. Lifetime is usually defined as the time, under specified operating conditions, at which either the capacitance decreases by a specified percentage, or the ESR increases by a specified percentage. Either of these conditions is considered a "failure". By this definition a capacitor could "Fail" and still operate perfectly in a circuit. Most designers specify a capcaitance that is higher than required in order to allow for degradation in capacitance over time. Similarly, a capacitor with a lower than required ESR is usually specified. See the following site for a detailed explanation of what's going on.
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**broken link removed**
Regards,
Kral

Added after 3 minutes:

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