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Electrolytic Capacitor failure

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Electrolytic Capacitor failure

As Harlan pointed out - I was an engineer for the FAA until retirement -
We changed electrolytics as part of normal PM's on critical systems
usually every 5 years or so. CDE (Cornell Dubilier) indicates expected
life (MTBF) of devices operated within rated voltage & temp specs to be
about 80-100 thousand hours. Most failures occur quickly around the end
of that period. For 24/7 operated systems, that translates to around
8-10 years before rapid EOL failures begin to occur. Electrolytics can
be thought of like incandescent lamps - they have a finite useful life
and the fail quickly around the end of that time. ESR (Equivalent Series
(AC) resistance) increases which reflects in higher ripple currents in
power supplies are a main culprit. Check out:
https://www.cde.com/resources/technical-papers/reliability.pdf
73 Gill W4RYW

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Elecraft mailing list

Re: Electrolytic Capacitor failure

Hello Gill
Doing reliability calculations to MIL 217 was very instructive many years ago and it taught me that operating well under the limits extended MTBF a lot. Some military customers instructed that specs were 60% or more degraded to achieve longer service life. What was your experience of that? It amazes me that amateur psus last so long! Then, again, they are rarely continuously operated 24/7.
73
David G3UNA/G6CP

> On 16 April 2020 at 15:19 Gill via Elecraft <[hidden email]> wrote:
>
>
> As Harlan pointed out - I was an engineer for the FAA until retirement -
> We changed electrolytics as part of normal PM's on critical systems
> usually every 5 years or so. CDE (Cornell Dubilier) indicates expected
> life (MTBF) of devices operated within rated voltage & temp specs to be
> about 80-100 thousand hours. Most failures occur quickly around the end
> of that period. For 24/7 operated systems, that translates to around
> 8-10 years before rapid EOL failures begin to occur. Electrolytics can
> be thought of like incandescent lamps - they have a finite useful life
> and the fail quickly around the end of that time. ESR (Equivalent Series
> (AC) resistance) increases which reflects in higher ripple currents in
> power supplies are a main culprit. Check out:
> https://www.cde.com/resources/technical-papers/reliability.pdf
> 73 Gill W4RYW
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

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Leroy

Re: Electrolytic Capacitor failure

In reply to this post by Elecraft mailing list

I also retired from FAA. Maybe the Air Defense Long Range ARSR 4 RADARs ,
BI-6, MODE-S and dozens of other 24/7 sytems, are not "critical systems".
Power supply issues were rare. Some of the most robust supplies I have ever
experienced.
Every ham shack I have ever seen has at least one bad one under the bench.

What destroyed the FAA is fanatical political correctness.

73 Leroy AB7CE

-----Original Message-----
From: Gill via Elecraft
Sent: Thursday, April 16, 2020 8:19 AM
To: [hidden email]
Subject: [Elecraft] Electrolytic Capacitor failure

As Harlan pointed out - I was an engineer for the FAA until retirement -
We changed electrolytics as part of normal PM's on critical systems
usually every 5 years or so. CDE (Cornell Dubilier) indicates expected
life (MTBF) of devices operated within rated voltage & temp specs to be
about 80-100 thousand hours. Most failures occur quickly around the end
of that period. For 24/7 operated systems, that translates to around
8-10 years before rapid EOL failures begin to occur. Electrolytics can
be thought of like incandescent lamps - they have a finite useful life
and the fail quickly around the end of that time. ESR (Equivalent Series
(AC) resistance) increases which reflects in higher ripple currents in
power supplies are a main culprit. Check out:
https://www.cde.com/resources/technical-papers/reliability.pdf
73 Gill W4RYW

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EricJ-2

Re: Electrolytic Capacitor failure

In reply to this post by Elecraft mailing list

They are rarely operated 24/7, and they aren't usually supervised by
career engineers. Most hams are relatively inexperienced hobbyists who
may not recognize a problem until it is catastrophic. Someone in this
thread already mentioned that nearly all ham shacks have a bad
electrolytic lurking under the bench.

Eric KE6US

On 4/16/2020 7:38 AM, CUTTER DAVID via Elecraft wrote:

> Hello Gill
> Doing reliability calculations to MIL 217 was very instructive many years ago and it taught me that operating well under the limits extended MTBF a lot. Some military customers instructed that specs were 60% or more degraded to achieve longer service life. What was your experience of that? It amazes me that amateur psus last so long! Then, again, they are rarely continuously operated 24/7.
> 73
> David G3UNA/G6CP
>
>> On 16 April 2020 at 15:19 Gill via Elecraft <[hidden email]> wrote:
>>
>>
>> As Harlan pointed out - I was an engineer for the FAA until retirement -
>> We changed electrolytics as part of normal PM's on critical systems
>> usually every 5 years or so. CDE (Cornell Dubilier) indicates expected
>> life (MTBF) of devices operated within rated voltage & temp specs to be
>> about 80-100 thousand hours. Most failures occur quickly around the end
>> of that period. For 24/7 operated systems, that translates to around
>> 8-10 years before rapid EOL failures begin to occur. Electrolytics can
>> be thought of like incandescent lamps - they have a finite useful life
>> and the fail quickly around the end of that time. ESR (Equivalent Series
>> (AC) resistance) increases which reflects in higher ripple currents in
>> power supplies are a main culprit. Check out:
>> https://www.cde.com/resources/technical-papers/reliability.pdf
>> 73 Gill W4RYW
>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
> .

Elecraft mailing list

Re: Electrolytic Capacitor failure

In reply to this post by Elecraft mailing list

Hi David,
I was a civilian Electrical Engineer with the US Army before the FAA
stint. We absolutely required the components used in critical systems to
be operated well below the "rated" thresholds. I did HV substation
design for places such as Marshall Space Flight Center and Redstone
Arsenal - the Army missle development center where the original Redstone
rocket was developed to launch the USA's 1st satellite in 1958. I was
bombarded by manufacturers wanting us to use the 'latest' electronic
versions of the substation protective relaying systems in the 1990's
which until then had been totally analog. I refused to allow that then,
primarily because they relied on electrolytic capacitors in their 'power
supply' & 'transient bypass' systems (internally to the relay). The
electrolytic caps were the weak link. A 161Kv substation is no place for
components sensitive to transients & guaranteed to fail after 10 yrs or
so. Those same caps have destroyed more PC motherboards, HD TV sets,
etc. than any other cause. I have a ESR meter which allows one to check
PC board caps in circuit - It uses an AC low level voltage which will
not cause semiconductors to activate, & which gives ESR values for the
caps. We used to try to repair expensive PC boards in the FAA systems
rather that "board changing". That way we could keep one good spare &
fix the failed one when replaced, keeping it as the spare. Electrolytic
Cap's were the main culprits in the failures.
Thanks for the reply!
73 Gill

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