What happens when electrolytic capacitors 'dry out'?

D

/dev/phaeton

Guest
I hear about this a lot when it comes to old amplifier equipment. "The
caps were dried out in my 1971 Doumaflauuchi Quadraphonic HiFi Set so I
had to replace them all".

Does this mean that the dielectric has met the destructive end of a slow
chemical reaction? Does it mean the capacitor package sprung a leak and
released whatever 'moisture' it had in it, thus changing its properties?
How long does it take for electrolytics to 'dry out'?

Are there any preventative measures, such as powering up the device every
few months to re-energize the plates?

Once the caps are all dried up, what are the options?

Replace them all with new?
Remove them, bake them in an oven, reinstall them?
Power up the circuit and leave it on in an 'idle state' for an extended
period of time?


Thanks, and sorry for the wordiness!

-ph
 
On Fri, 09 Nov 2007 05:52:44 +0000, /dev/phaeton wrote:

I hear about this a lot when it comes to old amplifier equipment. "The
caps were dried out in my 1971 Doumaflauuchi Quadraphonic HiFi Set so I
had to replace them all".

Does this mean that the dielectric has met the destructive end of a slow
chemical reaction? Does it mean the capacitor package sprung a leak and
released whatever 'moisture' it had in it, thus changing its properties?
How long does it take for electrolytics to 'dry out'?

Are there any preventative measures, such as powering up the device every
few months to re-energize the plates?

Once the caps are all dried up, what are the options?

Replace them all with new?
Remove them, bake them in an oven, reinstall them?
Power up the circuit and leave it on in an 'idle state' for an extended
period of time?


Thanks, and sorry for the wordiness!

-ph
Click to expand...
The mechanism by which an electrolytic capacitor "dries out" is that the
water in the electrolyte evaporates. This is just like the dregs in a
bottle of beer drying out, only with quote marks (and without the mold).

This "drying out" happens because all common* electrolytic capacitors
aren't hermetically sealed, and the electrolyte _does_ have to stay wet.

Electrolytic capacitors that don't dry out can lose their ability to
withstand voltage, because the oxide layer on the aluminum gradually goes
away**. When powering up equipment with high voltage electrolytics that
have been unused for a long time the capacitors must be "reformed" -- do a
web search for the procedure.

* I know wet-slug Tantalums, as produced for aerospace applications, are
sealed -- I know of no aluminum electrolytics that are so constructed.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
 
On 9 Nov, 05:52, /dev/phaeton <blahbleh...@hotmail.com> wrote:
I hear about this a lot when it comes to old amplifier equipment. "The
caps were dried out in my 1971 Doumaflauuchi Quadraphonic HiFi Set so I
had to replace them all".

Does this mean that the dielectric has met the destructive end of a slow
chemical reaction? Does it mean the capacitor package sprung a leak and
released whatever 'moisture' it had in it, thus changing its properties?
How long does it take for electrolytics to 'dry out'?

Are there any preventative measures, such as powering up the device every
few months to re-energize the plates?

Once the caps are all dried up, what are the options?

Replace them all with new?
Remove them, bake them in an oven, reinstall them?
Power up the circuit and leave it on in an 'idle state' for an extended
period of time?

Thanks, and sorry for the wordiness!

-ph
Click to expand...
As the water in the electrolyte dries out the internal resistance (ESR
- equivalent series resistance) of the capacitor increases and renders
it useless.

The following is a good explanation of what's happening:
http://www.sencore.com/custsup/pdf/TT104.pdf
 
"/dev/phaeton" <blahbleh666@hotmail.com> wrote in message
news:MASYi.155$RO1.153@newsfe05.lga...
I hear about this a lot when it comes to old amplifier equipment. "The
caps were dried out in my 1971 Doumaflauuchi Quadraphonic HiFi Set so I
had to replace them all".

Does this mean that the dielectric has met the destructive end of a slow
chemical reaction? Does it mean the capacitor package sprung a leak and
released whatever 'moisture' it had in it, thus changing its properties?
How long does it take for electrolytics to 'dry out'?

Are there any preventative measures, such as powering up the device every
few months to re-energize the plates?

Once the caps are all dried up, what are the options?

Replace them all with new?
Remove them, bake them in an oven, reinstall them?
Power up the circuit and leave it on in an 'idle state' for an extended
period of time?


Thanks, and sorry for the wordiness!

-ph
Click to expand...
Replace all the electrolytic caps in old equipment before you even power up
the unit.
A bad cap can do more damage like fry coils etc.

Tom
 
Thanks for all the help and PDFs, everyone.


Quick question- Does use or lack of use have any effect on how soon
caps dry out? I.e, should I power up all my amplification devices at
least once a month or so as a preventative measure?

thx

-phaeton
 
"phaeton"

Quick question- Does use or lack of use have any effect on how soon
caps dry out?
Click to expand...

** Time and ambient temperature are the causes.

But most electros last a couple of decades, just fine.


I.e, should I power up all my amplification devices at
least once a month or so as a preventative measure?
Click to expand...


** Lack of use and storage in damp places *damages electronics*.
Condensation forms on metal parts and initiates surface corrosion and rust
spots. All connectors, pots ad switches are damaged by this.

Electro caps can "depolarise" after a long period in storage, then overheat
and fail when the item next turned on.

Occasional use is best, plus storage in a warm, dry environment.




....... Phil
 
phaeton wrote:
Thanks for all the help and PDFs, everyone.

Quick question- Does use or lack of use have any effect on how soon
caps dry out? I.e, should I power up all my amplification devices at
least once a month or so as a preventative measure?
Click to expand...

Heat causes the seals do dry out and fail.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
the elctrolyte inside between the foils that comprise the two "plates"
actually has a liquid that dries out over time. they are usually sealed well
enough to last 20-30 yrs, but beyond that it is very iffy and prone to
catastrophic failure (short) or in some cases they act like no capacitor
exists in their place. (open)

some are actually "vented" to prevent bursting the can, (they make quite a
mess of things when they do explode too!) if overvoltaged or heat makes
them fail.

my uncles old 1920's RCA radio (36 inch x 20 inch x 20 inch behemoth)
actually had brilliant chrome plated steel covers over each can capacitor
and tube.

they just have a "lifetime" and will eventually fail. this is really old
stuff u must remebr, way before xixtors and micropowered amps.
 
Michael A. Terrell wrote:

phaeton wrote:

Thanks for all the help and PDFs, everyone.

Quick question- Does use or lack of use have any effect on how soon
caps dry out? I.e, should I power up all my amplification devices at
least once a month or so as a preventative measure?



Heat causes the seals do dry out and fail.

Yup, built in obsolescence. Just install a few near a
Click to expand...
heated area so that you can buy a new MB later on because
every knows with in a short time, MS will have your MB
hogged down any ways.

What marketing tactics.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
 
Jamie wrote:
Michael A. Terrell wrote:

phaeton wrote:

Thanks for all the help and PDFs, everyone.

Quick question- Does use or lack of use have any effect on how soon
caps dry out? I.e, should I power up all my amplification devices at
least once a month or so as a preventative measure?



Heat causes the seals do dry out and fail.

Yup, built in obsolescence. Just install a few near a
heated area so that you can buy a new MB later on because
every knows with in a short time, MS will have your MB
hogged down any ways.

What marketing tactics.
Click to expand...

Where would YOU put them? On the opposite corner of the MB? They
are close to the CPU's voltage regulator and CPU, because the HAVE to
be. Trace inductance and resistance would make the CPU unstable if it
wasn't right next to the CPU.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
The biggest problem I have found with electrolytics is they go short
circuit blowing the fuse.
 
Yup, built in obsolescence. Just install a few near a heated area so
that you can buy a new MB later on because every knows with in a short
time, MS will have your MB hogged down any ways.

What marketing tactics.
Click to expand...
No Microsoft here.

-phaeton
 
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