Re: [PSES] Capacitor Friday question

2020-01-18 Thread John Allen 
Yup

 

Old electrolytics need “time” and, IIRC, a gradually increasing voltage to 
reform before one applies the “full voltage”!  

 

I’ve probably told this story before, but, when at school “some  decades” ago I 
built a valve/tube oscillator from stuff in a “junk pile” that I had bought 
from a local old guy, but I didn’t have a suitable HV (it needed around 
160-200V dc) supply to power it. So I took it to school and connected it to a 
working supply, and then left the room (luckily!) – 5-10 mins later there was a 
“big bang” from the room, went back there to find the whole place covered in Al 
foil from the capacitor which had “ejected” its contents “explosively” J.

 

That was a 1950’s era component, but I suspect that even somewhat later 
capacitors would probably have similar “issues” if not rejuvenated “carefully”!!

 

John E Allen

W. London, UK

 

From: Doug Powell [mailto:doug...@gmail.com] 
Sent: 18 January 2020 04:45
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Capacitor Friday question

 

Thanks Ken,

 

I had not realized anyone else on this forum had ever worked around vacuum 
tubes. Good to know.

 

Yes, I've always understood capacitor formation is a gradual thing. And 
especially not with high ripple current as is likely in the method described in 
the video. 

 

Doug

 

--

Douglas E Powell

doug...@gmail.com

https://www.linkedin.com/in/dougp01 


From: ibm...@gmail.com

Sent: January 17, 2020 8:32 PM

To: doug...@gmail.com

Cc: EMC-PSTC@listserv.ieee.org

Subject: Re: [PSES] Capacitor Friday question

 

Hi Doug!

Reforming capacitors is definitely a thing but it sounds like your skepticism 
comes from the allegation that capacitors can reform themselves in-circuit.  I 
think this is also 'a thing', though probably not recommended in the way shown 
in the video (dumping full line voltage across the equipment and waiting).  I 
recall hearing a common suggestion for working on older (vacuum tube) radios 
and such; that it was a good idea to bring them up slowly on a variac to allow 
for precisely this (capacitors to reform themselves).  

 

Another thing that rubs me the wrong way about the approach shown in the video: 
 If there's a question about a piece of equipment (whether old or new) it would 
be wise to open it up and check some things out first, even if only a visual 
inspection to look for bulged, vented, or leaky caps.  This is doubly a concern 
due to the industry-wide problem of 'capacitor plague' from the 90's to the 
early 2000's.  The general public may only have tangentially been aware of this 
due to significant fallout in Dell computers, but many manufacturers were 
affected.  The story behind it is actually quite fascinating:  
https://www.theguardian.com/technology/blog/2010/jun/29/dell-problems-capacitors

 

-Ken

 

On Fri, Jan 17, 2020 at 8:22 PM Doug Powell  wrote:

This is somewhat off topic but still I feel it can be relevant to equipment 
reliability.

 

My daughter found this article on Facebook and successfully got her sewing 
machine running again, after a fairly long period of storage. The link  has an 
interesting theory about old electrolytic capacitors restoring themselves and 
I'm not sure I buy it. I've never heard of this before sort of thing before. 
What do you think? 

 

https://m.facebook.com/DrDavesSewingMachines/posts/1273259472698687

Have a great weekend. ~Doug

--

Douglas E Powell

doug...@gmail.com

https://www.linkedin.com/in/dougp01

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Re: [PSES] Capacitor Friday question

2020-01-17 Thread Doug Powell 
  Thanks Ken,I had not realized anyone else on this forum had ever worked around vacuum tubes. Good to know.Yes, I've always understood capacitor formation is a gradual thing. And especially not with high ripple current as is likely in the method described in the video.   Doug--Douglas E Powelldoug...@gmail.comhttps://www.linkedin.com/in/dougp01   From: ibm...@gmail.comSent: January 17, 2020 8:32 PMTo: doug...@gmail.comCc: EMC-PSTC@listserv.ieee.orgSubject: Re: [PSES] Capacitor Friday question  Hi Doug!Reforming capacitors is definitely a thing but it sounds like your skepticism comes from the allegation that capacitors can reform themselves in-circuit.  I think this is also 'a thing', though probably not recommended in the way shown in the video (dumping full line voltage across the equipment and waiting).  I recall hearing a common suggestion for working on older (vacuum tube) radios and such; that it was a good idea to bring them up slowly on a variac to allow for precisely this (capacitors to reform themselves).  Another thing that rubs me the wrong way about the approach shown in the video:  If there's a question about a piece of equipment (whether old or new) it would be wise to open it up and check some things out first, even if only a visual inspection to look for bulged, vented, or leaky caps.  This is doubly a concern due to the industry-wide problem of 'capacitor plague' from the 90's to the early 2000's.  The general public may only have tangentially been aware of this due to significant fallout in Dell computers, but many manufacturers were affected.  The story behind it is actually quite fascinating:  https://www.theguardian.com/technology/blog/2010/jun/29/dell-problems-capacitors-KenOn Fri, Jan 17, 2020 at 8:22 PM Doug Powell <doug...@gmail.com> wrote:This is somewhat off topic but still I feel it can be relevant to equipment reliability.My daughter found this article on Facebook and successfully got her sewing machine running again, after a fairly long period of storage. The link  has an interesting theory about old electrolytic capacitors restoring themselves and I'm not sure I buy it. I've never heard of this before sort of thing before. What do you think? https://m.facebook.com/DrDavesSewingMachines/posts/1273259472698687Have a great weekend. ~Doug  --Douglas E Powelldoug...@gmail.comhttps://www.linkedin.com/in/dougp01 
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Re: [PSES] Capacitor Friday question

2020-01-17 Thread IBM Ken 
Hi Doug!
Reforming capacitors is definitely a thing but it sounds like your
skepticism comes from the allegation that capacitors can reform themselves
in-circuit.  I think this is also 'a thing', though probably not
recommended in the way shown in the video (dumping full line voltage across
the equipment and waiting).  I recall hearing a common suggestion for
working on older (vacuum tube) radios and such; that it was a good idea to
bring them up slowly on a variac to allow for precisely this (capacitors to
reform themselves).

Another thing that rubs me the wrong way about the approach shown in the
video:  If there's a question about a piece of equipment (whether old or
new) it would be wise to open it up and check some things out first, even
if only a visual inspection to look for bulged, vented, or leaky caps.
This is doubly a concern due to the industry-wide problem of 'capacitor
plague' from the 90's to the early 2000's.  The general public may only
have tangentially been aware of this due to significant fallout in Dell
computers, but many manufacturers were affected.  The story behind it is
actually quite fascinating:
https://www.theguardian.com/technology/blog/2010/jun/29/dell-problems-capacitors

-Ken

On Fri, Jan 17, 2020 at 8:22 PM Doug Powell  wrote:

> This is somewhat off topic but still I feel it can be relevant to
> equipment reliability.
>
> My daughter found this article on Facebook and successfully got her sewing
> machine running again, after a fairly long period of storage. The link  has
> an interesting theory about old electrolytic capacitors restoring
> themselves and I'm not sure I buy it. I've never heard of this before sort
> of thing before. What do you think?
>
> https://m.facebook.com/DrDavesSewingMachines/posts/1273259472698687
>
> Have a great weekend. ~Doug
>
> --
>
> Douglas E Powell
>
> doug...@gmail.com
>
> https://www.linkedin.com/in/dougp01
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to 
> emc-p...@ieee.org
>
> All emc-pstc postings are archived and searchable on the web at:
> http://www.ieee-pses.org/emc-pstc.html
>
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
>
> Website: http://www.ieee-pses.org/
> Instructions: http://www.ieee-pses.org/list.html (including how to
> unsubscribe) 
> List rules: http://www.ieee-pses.org/listrules.html
>
> For help, send mail to the list administrators:
> Scott Douglas sdoug...@ieee.org
> Mike Cantwell mcantw...@ieee.org
>
> For policy questions, send mail to:
> Jim Bacher j.bac...@ieee.org
> David Heald dhe...@gmail.com
>

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[PSES] Capacitor Friday question

2020-01-17 Thread Doug Powell 
This is somewhat off topic but still I feel it can be relevant to equipment reliability.My daughter found this article on Facebook and successfully got her sewing machine running again, after a fairly long period of storage. The link  has an interesting theory about old electrolytic capacitors restoring themselves and I'm not sure I buy it. I've never heard of this before sort of thing before. What do you think? https://m.facebook.com/DrDavesSewingMachines/posts/1273259472698687Have a great weekend. ~Doug  --Douglas E Powelldoug...@gmail.comhttps://www.linkedin.com/in/dougp01 
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