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.

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Old August 25th 18, 06:04 AM posted to sci.electronics.repair
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Default Removing Large Electrolytics

On 2018/08/22 2:36 PM, Ron D. wrote:
Once you remove the solder "ADD MORE". Yep, add more. Suck that out.

It has the tendency to heat other areas.

You can also add a solder removal alloy form Chip-Quik.

You can break off the tabs sometimes. You can cut the can sometimes. I'd use these methods at last resort.

Solder with a low temperature allow after removing most of the solder and suck out is my best suggestion.


I too like the idea of using a small amount of Chip-Qick after first
removing as much solder as possible. This may make the solder bond so
weak that it will break out with very little force. If not, then dig out
a heat gun and secure the board - heating the area and pull on the
capacitor at the same time, I've done that by tying a weight to the item
to remove and let gravity do the work while I fart around with the heat
gun, etc.

John

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Old August 25th 18, 06:35 AM posted to sci.electronics.repair
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Default Replacing Large Electrolytics

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 of values 35V/3300uF which when stacked 2
high and wired in parallel occupy - fortunately - the same footprint as
the ones that failed.
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 size isn't cheap, but if you buy new ones, that's the end of your
repair.

https://www.mouser.com/ProductDetail/Vishay-Sprague/TVA1229?qs=%2fha2pyFadujX3auk1NrQ%2fV7hXwNYjanuW1q cIa3mLSA%3d


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Old August 25th 18, 11:43 AM posted to sci.electronics.repair
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Default Replacing Large Electrolytics

On Sat, 25 Aug 2018 00:35:34 -0500, Fox's Mercantile wrote:

Reforming is a fool's game.


Throwing away is a fool's game.

https://www.youtube.com/watch?v=nat1YYNMW5A

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Old August 25th 18, 02:32 PM posted to sci.electronics.repair
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Default Replacing Large Electrolytics

On Fri, 24 Aug 2018 19:06:43 -0700, tabbypurr wrote:

I'd get newer ones if possible. At that age they'll be dead or near to
it. In apps where high ESR is acceptable they last better, but still 40
is 80 human years for lytics.


I've always been of the view that it's excessive heat over long periods
of operation that eventually kills 'lytics. I don't see how them being in
store, albeit for many decades, could render them useless. But we shall
see! I'm currently reforming the NOS ones I have and will report back on
the results in due course.
Fortunately I'm not doing this for any customer; I'm only a hobbyist
working on my own stuff, so can easily afford to be proven wrong in this
if such should turn out to be the case. ;-)




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Old August 25th 18, 06:39 PM posted to sci.electronics.repair
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Default Replacing Large Electrolytics

On Saturday, August 25, 2018 at 9:32:35 AM UTC-4, Cursitor Doom wrote:
On Fri, 24 Aug 2018 19:06:43 -0700, tabbypurr wrote:

I'd get newer ones if possible. At that age they'll be dead or near to
it. In apps where high ESR is acceptable they last better, but still 40
is 80 human years for lytics.


I've always been of the view that it's excessive heat over long periods
of operation that eventually kills 'lytics. I don't see how them being in
store, albeit for many decades, could render them useless. But we shall
see! I'm currently reforming the NOS ones I have and will report back on
the results in due course.
Fortunately I'm not doing this for any customer; I'm only a hobbyist
working on my own stuff, so can easily afford to be proven wrong in this
if such should turn out to be the case. ;-)


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.

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.
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Old August 25th 18, 07:23 PM posted to sci.electronics.repair
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Default Replacing Large Electrolytics

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.





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Old August 25th 18, 08:19 PM posted to sci.electronics.repair
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Default Replacing Large Electrolytics

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.

John


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Old August 27th 18, 10:01 AM posted to sci.electronics.repair
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Default Replacing Large Electrolytics

On Sat, 25 Aug 2018 12:19:48 -0700, John Robertson
wrote:

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.

John


What is the model number of that Heathkit?

I ask because I have one of their cap testers, with an eye tube. I've
had it for a few years. I plugged it in when i got it and it lights up,
eye tube works, but I never put it to use. I'd tell you the model number
of mine, but I will have to dig it out of my storage shed.

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Old August 27th 18, 02:41 PM posted to sci.electronics.repair
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Default Replacing Large Electrolytics

On Saturday, August 25, 2018 at 6:43:47 AM UTC-4, Gunther Heiko Hagen wrote:
On Sat, 25 Aug 2018 00:35:34 -0500, Fox's Mercantile wrote:

Reforming is a fool's game.


Throwing away is a fool's game.

https://www.youtube.com/watch?v=nat1YYNMW5A


I won't watch that video because I KNOW Jeff is right: reforming is a fool's game. One may get away with reforming a cap to save a couple of bucks, but I'm more concerned about the collateral damage if this reformed cap returns to its leaky state and perhaps wipes out a power transformer.


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