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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Sep Wed 19, 2018 8:50 pm 
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allied333 wrote:
Rare, but I bought 4 bad new electrolytic capacitors. Leaked so bad it pulled down the voltage thru a resistor network. Another new cap fixed the problem.

There's a lesson to be learned there; always test new caps.

Awhile back I installed a new metallized polypropylene cap in a home-brew set I was building, and eventually determined that it's lack of performance was due to the cap being NG.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Sep Thu 20, 2018 12:27 pm 
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I even got a couple of bad caps with a brand new tone control kit from China, so ya, always check them.


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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Sep Thu 20, 2018 12:41 pm 
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Leigh wrote:
Some years ago, several major manufacturers produced entire runs of defective electrolytics.
This was due to a missing element in the chemistry of the electrolyte.

Hopefully all of those are in landfills, but you never know.

It's always possible for problems to exist on a smaller scale and get by Quality Control.
Of course, that assumes the manufacturer has such a department in the first place.

- Leigh

I remember this well! IBM/Lenovo used them in their motherboards and ended up replacing many defective units and causing me a bunch of grief. As I recall the caps were "Chinese Made" using stolen Japanese technology minus that key ingredient. Every one of the caps had stuff leaking out of the blown tops.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Sep Thu 20, 2018 10:00 pm 
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The company I worked for was one of the companies that did service work for IBM/Lenovo. Laptop-Desktop systems. We had so much work that we had to hire contractors who got paid by the job. They would show the manager how to spot the bubbled top and put in a service call. They made a ton of money that year. Sony got nailed also, but not to the extent that IBM did. We serviced Apple too and I never saw one mother board with bulging cap. I hated Apple because they were a bear to work on, but they put out a quality product. Our sale people would sign any contract and I've worked on some real junk. Gateway-- You carried Band-Aids and antiseptic in the van.

Freeman


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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Sep Sun 23, 2018 11:22 pm 
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Location: Detroit, Michigan
I Worked for DEC/Compac, and we had a customer who had thousands of LG pc's under service contract. One particular generation got hit with the capacitor plague. The service philosophy was sub-assembly replacement, I lost count of how many motherboards I replaced, got to be in the many hundreds. Some caps would bulge the top vents, some would leak the brown electrolyte, some would blow the cans clean off, and others would blow and unwind the insides. I have to say, good job security while it lasted.


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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Sep Mon 24, 2018 4:31 am 
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Kevin Clark wrote:
The service philosophy was sub-assembly replacement, I lost count of how many motherboards I replaced, got to be in the many hundreds.

Board swapping in consumer electronics became a cost cutting measure back in the '70's, as lesser skilled (and paid) personnel could do that, vs paying a tech to do component level troubleshooting. Not at all surprising that it carried over into PC's.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Oct Sun 28, 2018 2:16 pm 
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HERSHEY wrote:
I just want to offer the suggestion to all to check those new electrolytics before you install them. In the last 6 months, I've put into 2 radios new electrolytics that were bad.


Leigh wrote:
Some years ago, several major manufacturers produced entire runs of defective electrolytics.
This was due to a missing element in the chemistry of the electrolyte.
...
- Leigh


The best way to test (electrolytic) capacitors; measure ESR:
https://en.wikipedia.org/wiki/Equivalent_series_resistance


Capacitor Testing, Safe Discharging and Other Related Information
Version 2.42 (22-Nov-05):
http://www.repairfaq.org/sam/captest.htm
Quote: "...
Before I bought my ESR meter I too wondered--what exactly did it measure? Nevertheless, having heard so much about the meter, I went ahead and bought one. It works, and that's the real bottom line.
...
The objective of the ESR meter is to identify capacitors that have gone bad. This is more the case with electrolytics where the dielectric compound tends to dry up.
..."

An Equivalent Series Resistance Meter:
http://ludens.cl/Electron/esr/esr.html
Quote: "...With my ESR meter I quickly found five electrolytic capacitors which had degraded a lot...one had 6 Ohm, one 7 Ohm, and the other two had such high ESR that the meter wouldn't even deflect!..."

An AC-coupled ESR-tester can also test battery/accumulator cells:

Hints for techs using Bob Parker's ESR meter(kit)...:
https://web.archive.org/web/20170613142945/https://www.flippers.com/esrkthnt.html
http://www.flippers.com/esrkthnt.html
Quote: "...Bob Parker's excellent ESR meter (January 1996) will also test all types of cells and batteries..."

E.g.:

Good and simple:
Analogue ESR-meter - in the right side of the schematic there is a table with max. ESR:
https://web.archive.org/web/20161209090646/http://members.shaw.ca/swstuff/esrschematic.png
Description: Capacitor ESR Tester:
https://web.archive.org/web/20160621020936/http://members.shaw.ca:80/swstuff/esrmeter.html

-

A super de luxe component tester, including ESR and electrolytic capacitors, with AVR-microcontroller and source code in two different versions. The schematic can be found in many versions - even of manufactured versions. Warning: The tester do not survive plugging in a charged capacitor :shock: I acquired two just in case:

Transistor tester (actually much more than a transistor tester; a component tester):
Main description:
http://www.mikrocontroller.net/articles/AVR_Transistortester
Former description:
http://www.mikrocontroller.net/articles/AVR-Transistortester
Manual:
https://www.mikrocontroller.net/articles/AVR_Transistortester#Downloads_.28English.29
Source code:
http://www.mikrocontroller.net/svnbrowser/transistortester/

The Transistor tester can be bought at Ebay in many versions (LCD types; graphics, monochrome, color... Case og no case) - e.g.:

Through-hole version (Red PCB):
https://www.ebay.com/sch/i.html?&_nkw=Transistor+tester+gm328

SMD version (black PCB):
https://www.ebay.com/sch/i.html?&_nkw=Transistor+tester+gm328A

-

Capacitor plague:
https://en.wikipedia.org/wiki/Capacitor_plague
Quote: "...
The capacitor plague was a problem related to a higher-than-expected failure rate of non-solid aluminum electrolytic capacitors, between 1999 and 2007, especially those from some Taiwanese manufacturers,[1][2] due to faulty electrolyte composition that caused corrosion accompanied by gas generation, often rupturing the case of the capacitor from the build-up of pressure.
..."

Strategies to Repair or Replace Old Electrolytic Capacitors
https://web.archive.org/web/20180106070321/https://www.nmr.mgh.harvard.edu/~reese/electrolytics/
Quote: "...
Electrolytics do not suffer idleness well. They can cause big trouble when idle for long periods, needing periodic charging to stay "formed" and maintain the oxide layer that insulates the conducting plates. Sometimes they can be "reformed" by a slowly rising return to working voltage (see below). Even with regular use, electrolytics fail with age by drying out or leaking electrolyte following internal corrosion. If the electrolytic bulges, shows obvious loss of electrolyte, or simply can't be reformed you must replace it.
...
Reforming
..."

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Feb Sat 09, 2019 11:53 am 
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Posts: 669
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BikeNEPA wrote:
Leigh wrote:
Some years ago, several major manufacturers produced entire runs of defective electrolytics.
This was due to a missing element in the chemistry of the electrolyte.

Hopefully all of those are in landfills, but you never know.

It's always possible for problems to exist on a smaller scale and get by Quality Control.
Of course, that assumes the manufacturer has such a department in the first place.

- Leigh

I remember this well! IBM/Lenovo used them in their motherboards and ended up replacing many defective units and causing me a bunch of grief. As I recall the caps were "Chinese Made" using stolen Japanese technology minus that key ingredient. Every one of the caps had stuff leaking out of the blown tops.


So did Dell. I replaced a few of this type 'low ESR' cap on the
mother board of an old Dell XPS600 that I was given. They
were leaking electrolyte on top, having vented just enough
to relieve pressure.

David

P.S. Testing ESR is a good idea. I have several of the inexpensive
Chinese multi-function testers. One of them, which tests a variety
of electronic components such as diodes and transistors, also
tests resistance and capacitance, and it seems to have a pretty
good ESR testing feature. How accurate it is I have no idea- but it
does a good job, I believe, in Identifying caps with ESR problems.
It's amazing just how cheap these various tester boards are, for
what they do!

I routinely measure electrolytics for capacitance and then reform
them to make sure I get an acceptably low and steady leakage
reading. I don't that often test for ESR, but I probably should.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Apr Sat 20, 2019 3:08 pm 
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Location: dayton oh usa
i guess you never got to service the g4,g5,and early intel imacs then.
i recapped hundreds of those boards.
nothing compared to dell gx 270 and 280 but the fact is that every mfr got bit by cap plague even if they went with japanese caps.
the duds in the imac were nippon chemicon.
kzg and kzj series.
i have a video i made of me pouring a huge bin of new ones into the dumpster.
Freeman wrote:
The company I worked for was one of the companies that did service work for IBM/Lenovo. Laptop-Desktop systems. We had so much work that we had to hire contractors who got paid by the job. They would show the manager how to spot the bubbled top and put in a service call. They made a ton of money that year. Sony got nailed also, but not to the extent that IBM did. We serviced Apple too and I never saw one mother board with bulging cap. I hated Apple because they were a bear to work on, but they put out a quality product. Our sale people would sign any contract and I've worked on some real junk. Gateway-- You carried Band-Aids and antiseptic in the van.

Freeman


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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Apr Sat 20, 2019 4:45 pm 
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I check all components (resistors, capacitors, inductors,) befor installing in a rebuild. After all the trouble removing defective part, it is a minor step to test the replacement part, and even interesting. Particularly electrolytics at rated voltage for leakage. It's a lot easier befor getting them buried in a chassis and have to trouble shoot and then remove again. :evil:
EDIT: Including volume control pots.
This is the 500K volume pot before DeoxitD5 cleaning and after cleaning. Connected across a 12 VDC and turning the shaft through full rotation with scope on wiper connection.


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rsz_volume_pot_after.jpg [ 36.57 KiB | Viewed 1502 times ]

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Apr Sat 20, 2019 6:30 pm 
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Here's an electrolytic story... not to my credit!
A few weeks ago I rescued an AKAI A-05 AM/FM tuner from the kerbside... nice little unit, analog tuning with ganged tuning caps (not inductors.)
Main on/off switch was dead... Later, I replaced it; got lucky with a scrap P/B switch to hand that fitted.
I powered it up on a variac and it worked fine... so far, so good.
Then I found a leaking B+ filter electrolytic that had corroded the PCB! It was 2,200 uF, 25 VDC. I took it out and cleaned up the PCB under it (both sides.) I tested the electrolytic and it still tested good, no signs of continued leakage from case, full capacitance and <1 mA leakage at 25 volts. So, like an idiot, I put it back! Don't ask why and please don't throw things... we all have brain farts!
Then I used the tuner frequently... but that cap was nagging at me, so I finally got around to replacing it yesterday from new stock. I had three of this exact value to hand.
I reformed all three, but noticed that they all took a very long time to form and get to <1 mA leakage at 25 volts. I also tested the leaky one again... it very quickly dropped to <1 mA leakage and still measured about over 2200 uF. I threw it out!
The lessons for me... even though I already knew them:
Don't keep old electrolytics; however nicely they beg and plead to be kept. Throw them out!
Do reform all new electrolytics before use... if they don't need it, you'll see it and no harm is done. If they do need reforming, better it be done on the cap tester than on the first power-up inrush.
I'll end with one of my favorite aphorisms... becoming a cliche, I think:
"Q. How do you test an old electrolytic cap? Ans: throw it into an empty metal trash can. If it goes 'clang' then it's dead."
Cheers,
Roger

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Apr Wed 24, 2019 7:03 am 
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+1 on the reforming of electrolytics prior to installing them.

I've had really good luck with the new replacement filter caps I've bought over the years, but if I recall correctly I have had a couple that tested to have excess leakage right out of the package. Doesn't take but a few minutes to test them, you know the old adage, an ounce of prevention is worth a pound of cure.

Tom

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Jun Sun 09, 2019 8:26 pm 
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I always test for value and e.s.r. I have found batches that were too low or high value to use. I have some 22uf's that measured 25-26uf,way too high to use for a 16uf replacement. Usually the e.s.r. isn't bad. Also some 47's were too low. Usually the 1,3,5,uf caps are spot on.


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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Jun Mon 10, 2019 7:43 pm 
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Zenith Royal wrote:
I always test for value and e.s.r. I have found batches that were too low or high value to use. I have some 22uf's that measured 25-26uf,way too high to use for a 16uf replacement. Usually the e.s.r. isn't bad. Also some 47's were too low. Usually the 1,3,5,uf caps are spot on.

Why do you feel a 25uf is "too high" to replace a 16uf with?
( early electrolytic caps can vary as much as 50-100% in value)
(generally speaking) ...Depending on the application "larger" may actually be better.
If you are talking about an AC/to DC power supply filter capacitor in a "pi filter" configuration one stage away from a tube-rectifier ... the larger the capacitor the better. However if it is the 1st cap after the rectifier maybe not, depending on the rating of the tube.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Jun Mon 10, 2019 8:58 pm 
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Zenith Royal wrote:
I always test for value and e.s.r. I have found batches that were too low or high value to use. I have some 22uf's that measured 25-26uf,way too high to use for a 16uf replacement. Usually the e.s.r. isn't bad. Also some 47's were too low. Usually the 1,3,5,uf caps are spot on.

I would suggest that it depends on the circuit being worked on. If we are talking filter caps in an AC operated tube set, then perhaps. However with solid state equipment, i.e., Transistor radios, I've replaced using whatever I happen to have on hand; 47's for 10's, 10's for 30's, etc. The only cap I try to keep within a reasonable range is the one going to the wiper of the VC, which is usually a low value.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Jun Tue 11, 2019 12:20 am 
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I was talking about transistor radios. It that works for you then fine. Normally for a 16uf I'd use use a 15 that tests at least 16 or better.


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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Jun Tue 11, 2019 7:10 am 
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Zenith Royal wrote:
I was talking about transistor radios. It that works for you then fine. Normally for a 16uf I'd use use a 15 that tests at least 16 or better.

Sometime, experiment for your own edification; try a 10 in place of the 16, then try a 33, then a 47. Odds are, you won't notice any difference.

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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Sep Sat 14, 2019 7:12 pm 
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I have recently bought electrolytics from a reputable electronics store. They were “Jackcon” branded caps in sealed “NTE” packaging. I recall Jackcon was blacklisted during the capacitor plague a decade ago. Tested good, no problems so far, so maybe the company has reformed (pun intended) it’s behavior from its past bad practices.


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 Post subject: Check your new electrolytics before installing
PostPosted: Nov Tue 05, 2019 1:03 am 
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Jesus you know life sucks when the easiest “mod” goes wrong lmao

I would say just take time to triple check if everything is clean and tight. Wouldn’t worry about it too much. Also, wouldn’t listen to the tech...or take your car there again. Too much back pressure? If that’s the case, every single car with an aftermarket catback would have a check engine light lol


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 Post subject: Re: Check your new electrolytics before installing
PostPosted: Nov Sun 10, 2019 4:24 am 
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For those who might want to learn more about reforming caps:

https://youtu.be/ifWfvaIbWZY

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