Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #51   Report Post  
Old September 1st 18, 08:48 PM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Sep 2006
Posts: 612
Default Removing Large Electrolytics

On 08/28/2018 01:47 PM, Cursitor Doom wrote:
On Wed, 22 Aug 2018 04:03:23 -0700, tabbypurr wrote:

Sounds about par for the course. Go back further to paper caps and it'd
be a surprise to find any still working properly. And yes, micamold were
paper caps.


I've got a box full of the oil & paper caps that come in cubiod cans and
they all tested fine (I have an awful lot of vintage spares here). Not so
sure about the tubular paper caps which I assume you're talking about,
though.


Moisture + acid paper + foil = mess. That'll take a lot longer if the
cap has metal on five sides.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com


  #52   Report Post  
Old September 1st 18, 11:56 PM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jan 2015
Posts: 10,203
Default Removing Large Electrolytics

On Saturday, 1 September 2018 20:48:34 UTC+1, Phil Hobbs wrote:
On 08/28/2018 01:47 PM, Cursitor Doom wrote:
On Wed, 22 Aug 2018 04:03:23 -0700, tabbypurr wrote:

Sounds about par for the course. Go back further to paper caps and it'd
be a surprise to find any still working properly. And yes, micamold were
paper caps.


I've got a box full of the oil & paper caps that come in cubiod cans and
they all tested fine (I have an awful lot of vintage spares here). Not so
sure about the tubular paper caps which I assume you're talking about,
though.


Moisture + acid paper + foil = mess. That'll take a lot longer if the
cap has metal on five sides.

Cheers

Phil Hobbs


My prewar metal can paper caps are all wax sealed, and every last one tested dead as a very dead thing. The non-metal seal is where it can go wrong. Not sure why they didn't use bitumen.


NT
  #53   Report Post  
Old September 2nd 18, 09:15 AM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jan 2007
Posts: 1,887
Default Replacing Large Electrolytics

On Friday, August 24, 2018 at 10:35:43 PM UTC-7, Fox's Mercantile wrote:
On 8/24/18 6:42 PM, Cursitor Doom wrote:
I had 3 faulty electrolytics; all 30V/5500uF. In my spares bin I found 6
NOS (new old stock) electros ...
These spares, though unused, are probably 40 years old. Will they need re-
forming gradually over 24hrs before installing?


Reforming is a fool's game.
They either work to being with or they're bad.


That's not ny experience; yes, I might toss the 40--year-olds, but only
because new ones are cheap and probably better performing.
Even one-year-old capacitors can benefit from reforming, though,
and for some uses (timing capacitors) it's beneficial.

It doesn't take 24 hours, though: with a current-limited supply, just
give 'em 150% of the rated voltage and warm 'em with a hair
dryer for a few minutes, while watching the leakage current.
You can see it drop from milliamps to microamps.
  #54   Report Post  
Old September 2nd 18, 12:03 PM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Dec 2017
Posts: 377
Default Replacing Large Electrolytics

On 9/2/18 3:15 AM, whit3rd wrote:
It doesn't take 24 hours, though: with a current-limited supply, just
give 'em 150% of the rated voltage and warm 'em with a hair
dryer for a few minutes, while watching the leakage current.
You can see it drop from milliamps to microamps.


That's not how manufacturing does it.
Their installed and at the end of assembly line, full power is applied.
They either work or they don't.



--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com
  #55   Report Post  
Old September 2nd 18, 12:45 PM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Oct 2016
Posts: 40
Default Replacing Large Electrolytics

On Sun, 2 Sep 2018 06:03:04 -0500, Fox's Mercantile
wrote:

On 9/2/18 3:15 AM, whit3rd wrote:
It doesn't take 24 hours, though: with a current-limited supply, just
give 'em 150% of the rated voltage and warm 'em with a hair
dryer for a few minutes, while watching the leakage current.
You can see it drop from milliamps to microamps.


That's not how manufacturing does it.
Their installed and at the end of assembly line, full power is applied.
They either work or they don't.


I remember when part of my job was fixing power supplies. Some that
failed the automatic part of the test last thing on one day would work
the day after.

I never found out why that happened but I assumed it was an
electrolytic so I changed the lot.

Steve

--
http://www.npsnn.com



  #56   Report Post  
Old September 2nd 18, 07:50 PM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Mar 2015
Posts: 2,476
Default Replacing Large Electrolytics

On Sun, 02 Sep 2018 06:03:04 -0500, Fox's Mercantile wrote:

That's not how manufacturing does it.
Their installed and at the end of assembly line, full power is applied.
They either work or they don't.


That's all very well for *brand new* capacitors!





--
This message may be freely reproduced without limit or charge only via
the Usenet protocol. Reproduction in whole or part through other
protocols, whether for profit or not, is conditional upon a charge of
GBP10.00 per reproduction. Publication in this manner via non-Usenet
protocols constitutes acceptance of this condition.
  #57   Report Post  
Old September 2nd 18, 08:38 PM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Apr 2018
Posts: 9
Default Removing Large Electrolytics

On 2018-08-28 10:47, Cursitor Doom wrote:
On Wed, 22 Aug 2018 04:03:23 -0700, tabbypurr wrote:

I've got a box full of the oil & paper caps that come in cubiod cans and
they all tested fine (I have an awful lot of vintage spares here).


Enjoy your PCBs.

  #58   Report Post  
Old September 2nd 18, 09:06 PM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jan 2015
Posts: 10,203
Default Removing Large Electrolytics

On Sunday, 2 September 2018 20:38:38 UTC+1, +++ATH0 wrote:
On 2018-08-28 10:47, Cursitor Doom wrote:


I've got a box full of the oil & paper caps that come in cubiod cans and
they all tested fine (I have an awful lot of vintage spares here).


Enjoy your PCBs.


and not the good type


NT
  #59   Report Post  
Old September 3rd 18, 03:36 AM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Jan 2007
Posts: 1,887
Default Replacing Large Electrolytics

On Sunday, September 2, 2018 at 4:45:44 AM UTC-7, Stephen Wolstenholme wrote:
On Sun, 2 Sep 2018 06:03:04 -0500, Fox's Mercantile
wrote:


[about electrolytic capacitors]

Their installed and at the end of assembly line, full power is applied.
They either work or they don't.


I remember when part of my job was fixing power supplies. Some that
failed the automatic part of the test last thing on one day would work
the day after.

I never found out why that happened but I assumed it was an
electrolytic so I changed the lot.


Electrolytics have to be formed (kept under bias for a period) before they
develop the dielectric (oxide) layer, AND that layer is continuously
renewed when they're under bias. On the shelf, however, it degrades.
Some switchmode power supplies (the old Apple II types) rely on
timing capacitors for startup sequencing, and the power filter electrolytics are
NOT the prime suspects when such a power supply doesn't work.

You can often fix those power supplies by leaving 'em turned on overnight.
The most plausible reason for this is that the timing capacitors (not the big
filter caps) have to be re-formed. This syndrome can't be improved with
new filter capacitors (I've tried). Once they work, they're reliable again.


  #60   Report Post  
Old October 1st 18, 09:50 AM posted to sci.electronics.repair
external usenet poster
 
First recorded activity by DIYBanter: Apr 2015
Posts: 78
Default Replacing Large Electrolytics

Once upon a time on usenet John Robertson wrote:
On 2018/08/25 11:23 AM, Cursitor Doom wrote:
On Sat, 25 Aug 2018 10:39:13 -0700, John-Del wrote:

Heat and charge cycles do affect a capacitor's life, but they're
not the only factors. Humans who smoke, drink, and do drugs have a
shorter life than those who don't, but we all will die eventually.


Hmmm. Not really a valid analogy!

I've had plenty of electros in stock go off value, become leaky,
and go up in ESR just from sitting in a nice quiet bin. I don't
install any cap without running through my Z meter, and I will toss
an entire lot of caps if one is bad.


I managed to find 8 electros in my bin that could used in parallel
to get the equivalent of the failed ones I've removed. I've checked
them all for ESR, leakage and Capacitance and the readings I've got
have come out indistinguishable from new caps of the same value &
voltage rating. I've picked the best 6 (with the lowest ESR) and am
re-forming them over the course of this weekend.
I'll report back in due course on the success (or failure) of this
method. I certainly wouldn't want to hit them with their rated
voltage straight away after so long in limbo as that *would* be
inviting disaster.


The final test is leakage, set the cap up with an ammeter in series
and put it on a power supply running around 75% of the rated maximum
voltage. Leakage should be very low after the cap has stabilized.

Here is a nice write-up:

https://www.nmr.mgh.harvard.edu/~reese/electrolytics/

Heathkit made a great cap checker that we use to check older off the
shelf NOS caps. Has the Magic-Eye tube and everything - except ESR.


Thanks for that link.
--
Shaun.

"Humans will have advanced a long, long way when religious belief has a cozy
little classification in the DSM*."
David Melville (in r.a.s.f1)
(*Diagnostic and Statistical Manual of Mental Disorders)




Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Longevity of electrolytics David Nebenzahl Electronics Repair 25 August 24th 09 05:54 AM
5 large electrolytics to give away hr(bob) [email protected] Electronics Repair 0 December 22nd 08 05:17 AM
Need large electrolytics Gareth Magennis Electronics Repair 7 August 6th 08 07:08 PM
Strange HV electrolytics from Electronics Goldmine boardjunkie Electronics Repair 2 January 23rd 07 12:59 AM
Replacing electrolytics Jerry G. Electronics Repair 4 June 16th 04 07:19 AM


All times are GMT +1. The time now is 02:48 AM.

Powered by vBulletin® Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright 2004-2019 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"

 

Copyright © 2017