Removing Large Electrolytics

[Ralph Mowery]

In article <plpekd$ka7$1@dont-email.me>,
pcdhSpamMeSenseless@electrooptical.net says...

This might be a good use for Chip Quik--it's a bismuth-based solder that
drops the liquidus point of a joint low enough that gentle use of a heat
gun will melt it.

Just make sure you get the type that is made to help remove solder.
They make all kinds of solder type products. Some are just tin/lead and
will not help in removal.

From what little I have looked at it, the removal type is very
expensive .

 

[John Robertson]

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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[Fox's Mercantile]

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%2fV7hXwNYjanuW1qcIa3mLSA%3d>


--
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Jeff-1.0
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http:foxsmercantile.com

 

[Gunther Heiko Hagen]

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

 

[Cursitor Doom]

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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[John-Del]

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.

 

[Cursitor Doom]

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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[John Robertson]

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 pinballers never die, they just flip out."

 

On Sat, 25 Aug 2018 12:19:48 -0700, John Robertson <spam@flippers.com>
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.

 

[John-Del]

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.

 

[Cursitor Doom]

On Mon, 27 Aug 2018 06:41:30 -0700, John-Del wrote:

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.

No one is suggesting trying to reform leaky capacitors!



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[Ralph Mowery]

In article <pm10m4$dcc$1@dont-email.me>, curd@notformail.com says...

No one is suggesting trying to reform leaky capacitors!

Doesn't the capacitors show the same effect as being leaky ?

From my understanding , the you start off at low voltage so the current
will not be very high and as the capacitor forms you up the voltage some
so the capacitor does not draw too much current.

My understanding is that the plates of the capacitor form a coating (for
not having a better word for it) on the plates when put under a DC
voltage.

I still believe in just replacing the 'bad' ones. Sometimes more harm
can be done to the equipment by doing the reforming process if done
wrong.

 

[John Robertson]

On 2018/08/27 2:01 AM, oldschool@tubes.com wrote:

On Sat, 25 Aug 2018 12:19:48 -0700, John Robertson <spam@flippers.com
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.

It is an IT-28. Has a Power Factor test which is useful for testing
power supply caps.

I can make a PDF of my manual if you are desperate...however I expect it
is online somewhere.

John :-#)#

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[Cursitor Doom]

On Mon, 27 Aug 2018 12:30:26 -0400, Ralph Mowery wrote:

Doesn't the capacitors show the same effect as being leaky ?

From my understanding , the you start off at low voltage so the current
will not be very high and as the capacitor forms you up the voltage some
so the capacitor does not draw too much current.

My understanding is that the plates of the capacitor form a coating (for
not having a better word for it) on the plates when put under a DC
voltage.

I still believe in just replacing the 'bad' ones. Sometimes more harm
can be done to the equipment by doing the reforming process if done
wrong.

I don't think you've read the thread right through. These are NOS caps
out of circuit. I've now reformed them all and they pass all the
applicable tests, so I'll be installing them in place of the dead ones
later this week.





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[Ralph Mowery]

In article <pm1jgs$gmf$1@dont-email.me>, curd@notformail.com says...

I still believe in just replacing the 'bad' ones. Sometimes more harm
can be done to the equipment by doing the reforming process if done
wrong.

I don't think you've read the thread right through. These are NOS caps
out of circuit. I've now reformed them all and they pass all the
applicable tests, so I'll be installing them in place of the dead ones
later this week.

It may be worth while on the NOS caps. I may even be tempted to give
that a try.

 

[Terry Schwartz]

Why you would put 40 year old caps into ANYTHING is beyond me. Reformed or not. They may "pass the tests" now but they will not hold up long term. Spend the $25 and get new parts. Unless, that is, you like doing things twice. Feel like risking that PCB again in 2 years?

 

[jfeng@my-deja.com]

On Monday, August 27, 2018 at 12:50:00 PM UTC-7, Terry Schwartz wrote:

...Spend the $25 and get new parts...
Here in Silicon Valley, it would be a lot less. 4700uF/35V and 5600uF/42V are both available at retail for under US$1 each.

The diagnosis is probably correct, and the OP is committed to replacing the original caps, but I do not remember seeing a claim that this actually fixed the problem. At this price and given the concern over the long term reliability of the junque-box parts, I would tack-solder these caps to verify that this does indeed fix the problem, but I would use the new parts for the "permanent" repair. Using reformed parts would be OK if the faulty ones were unobtanium.

 

[Fox's Mercantile]

On 8/27/18 8:41 AM, John-Del wrote:

I won't watch that video because I KNOW Jeff is right: reforming
is a fool's game.

Like John, I do this shit for a living, and I refuse to waste my
time, or reputation, with any "crack pot" repairs.



--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com

 

[Cursitor Doom]

On Mon, 27 Aug 2018 20:56:41 -0500, Fox's Mercantile wrote:

On 8/27/18 8:41 AM, John-Del wrote:
I won't watch that video because I KNOW Jeff is right: reforming is a
fool's game.

Like John, I do this shit for a living, and I refuse to waste my time,
or reputation, with any "crack pot" repairs.

If you're a professional repair tech, I can see why you would only use
new parts. But I'm just a ham; a hobbyist. And we hams have been
successfully reforming electros for many decades without any adverse
outcomes. Loads of info on the net it you care to look for it, but I'm
guessing since you're a pro you'll turn your nose up at the very thought!





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[pfjw@aol.com]

And we hams have been
successfully reforming electros for many decades without any adverse
outcomes.

That have been reported. Hams are a parsimonious lot. And, like many of us, they will refrain from publicizing silly mistakes.

Peter Wieck
Melrose Park, PA