I have just spent about 40m trying to unsolder an electro on the board of
the Tek 466 I'm currently working on. It showed a ESR of 45 ohms so I
needed to hook it out of circuit just to be doubly sure it was really
that bad.
The electros in question are all fairly large ones in the (linear) PSU
section. For some reason they've not used separate boards for the various
sub-circuits, so the PSU is just one area of a v.large board which also
has components for all sorts of other functions. Anyway, The cap in
question has 5 connections to the board: 3 equi-spaced ground tabs around
the outside that come straight from the case of the cap and the 2 + and -
wires close to the centre. Given 5 in total through-hole connections,
it's proving very difficult to remove the cap using suction pump and
solder braid cos I cannot wiggle it at all. The best solution IMO would
be to heat all 5 tabs at the same time whilst pulling the cap's case from
the other side until it breaks free. Is there any tool that enables you
to do this? I fear the amount of ****ing around I'm having to do
otherwise will lead to delamination of the PCB traces and an ugly mess.
I cannot even slip a junior hacksaw blade between the bottom of the cap
and the PCB and cut it free cos it's obscured by other components.



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Some people use a butane torch to heat the solder joints gently while pulling on the component. Practice this technique before you do it on something you want to save. I have done this for DIP ICs.

Since you are pretty sure it is bad, I would clip the leads, destroying the can beforehand if necessary.

On Wednesday, 22 August 2018 01:18:33 UTC+1, wrote:

Some people use a butane torch to heat the solder joints gently while pulling on the component. Practice this technique before you do it on something you want to save. I have done this for DIP ICs.

Since you are pretty sure it is bad, I would clip the leads, destroying the can beforehand if necessary.

A torch is a recipe for a badly burnt board. I've always been able to move a multi-legged component at least a tiny amount while melting one or more legs, and rock it back & forth, letting the board cool well if paper. The pcb is slightly flexible after all. Paper boards are weak, vulnerable to heat & the copper comes unglued when hot.

Maybe you could cut the 3 outer tabs off flush.


NT

On 08/21/2018 07:46 PM, Cursitor Doom wrote:
I have just spent about 40m trying to unsolder an electro on the board of
the Tek 466 I'm currently working on. It showed a ESR of 45 ohms so I
needed to hook it out of circuit just to be doubly sure it was really
that bad.
The electros in question are all fairly large ones in the (linear) PSU
section. For some reason they've not used separate boards for the various
sub-circuits, so the PSU is just one area of a v.large board which also
has components for all sorts of other functions. Anyway, The cap in
question has 5 connections to the board: 3 equi-spaced ground tabs around
the outside that come straight from the case of the cap and the 2 + and -
wires close to the centre. Given 5 in total through-hole connections,
it's proving very difficult to remove the cap using suction pump and
solder braid cos I cannot wiggle it at all. The best solution IMO would
be to heat all 5 tabs at the same time whilst pulling the cap's case from
the other side until it breaks free. Is there any tool that enables you
to do this? I fear the amount of ****ing around I'm having to do
otherwise will lead to delamination of the PCB traces and an ugly mess.
I cannot even slip a junior hacksaw blade between the bottom of the cap
and the PCB and cut it free cos it's obscured by other components.




+1 for can-opening it to save wear and tear on the board. If you
measure 45 ohms ESR in-circuit, it won't be better by itself.

Cheers

Phil Hobbs

On Tuesday, August 21, 2018 at 6:46:24 PM UTC-5, Cursitor Doom wrote:
I have just spent about 40m trying to unsolder an electro on the board of
the Tek 466 I'm currently working on. It showed a ESR of 45 ohms so I
needed to hook it out of circuit just to be doubly sure it was really
that bad.
The electros in question are all fairly large ones in the (linear) PSU
section. For some reason they've not used separate boards for the various
sub-circuits, so the PSU is just one area of a v.large board which also
has components for all sorts of other functions. Anyway, The cap in
question has 5 connections to the board: 3 equi-spaced ground tabs around
the outside that come straight from the case of the cap and the 2 + and -
wires close to the centre. Given 5 in total through-hole connections,
it's proving very difficult to remove the cap using suction pump and
solder braid cos I cannot wiggle it at all. The best solution IMO would
be to heat all 5 tabs at the same time whilst pulling the cap's case from
the other side until it breaks free. Is there any tool that enables you
to do this? I fear the amount of ****ing around I'm having to do
otherwise will lead to delamination of the PCB traces and an ugly mess.
I cannot even slip a junior hacksaw blade between the bottom of the cap
and the PCB and cut it free cos it's obscured by other components.



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Depending on what else is nearby, a heat gun can be effective.

I use a Metcal which is a 40 Watt iron very well controlled but when removing caps from computer motherboards where there are no thermal reliefs to the ground plane, NO soldering iron can unsolder it alone. The pin can't conduct the heat fast enough. I also have a cheap Chinese hot air tool. Set the temp on the air tool slightly below the melt temp so it won't 'blow' any SMD parts (none on the 466) off the board. This becomes a 2 handed operation.. While heating with the Metcal, I 'auxiliary' heat the board with the hot air tool for about 20 seconds. This WILL get hot enough to use your Edsyn Soldapullt to clear the hole and not lift any pads or damage the board.

Cutting up the cap and then removing the separate pins is OK IF you can destroy it without damaging the board. I've had excellent results with the aux heating technique which is faster than dismembering the part.

Torches are WAY too brutal especially in a Tek.

G²

On Tue, 21 Aug 2018 21:28:10 -0400, Phil Hobbs wrote:

+1 for can-opening it to save wear and tear on the board. If you
measure 45 ohms ESR in-circuit, it won't be better by itself.

Well, it's hardly surprising for an electro of this age. Clearly the
original component from a scope with a s/n indicating it was manufactured
44 years ago! What was more surprising was that only 2 out of 6 electros
in the PSU section showed abnormal readings (the remaining faulty one has
gone leaky).




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On Wednesday, 22 August 2018 11:12:10 UTC+1, Cursitor Doom wrote:
On Tue, 21 Aug 2018 21:28:10 -0400, Phil Hobbs wrote:

+1 for can-opening it to save wear and tear on the board. If you
measure 45 ohms ESR in-circuit, it won't be better by itself.

Well, it's hardly surprising for an electro of this age. Clearly the
original component from a scope with a s/n indicating it was manufactured
44 years ago! What was more surprising was that only 2 out of 6 electros
in the PSU section showed abnormal readings (the remaining faulty one has
gone leaky).

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.


NT

On Tuesday, August 21, 2018 at 9:28:19 PM UTC-4, Phil Hobbs wrote:
On 08/21/2018 07:46 PM, Cursitor Doom wrote:
I have just spent about 40m trying to unsolder an electro on the board of
the Tek 466 I'm currently working on. It showed a ESR of 45 ohms so I
needed to hook it out of circuit just to be doubly sure it was really
that bad.
The electros in question are all fairly large ones in the (linear) PSU
section. For some reason they've not used separate boards for the various
sub-circuits, so the PSU is just one area of a v.large board which also
has components for all sorts of other functions. Anyway, The cap in
question has 5 connections to the board: 3 equi-spaced ground tabs around
the outside that come straight from the case of the cap and the 2 + and -
wires close to the centre. Given 5 in total through-hole connections,
it's proving very difficult to remove the cap using suction pump and
solder braid cos I cannot wiggle it at all. The best solution IMO would
be to heat all 5 tabs at the same time whilst pulling the cap's case from
the other side until it breaks free. Is there any tool that enables you
to do this? I fear the amount of ****ing around I'm having to do
otherwise will lead to delamination of the PCB traces and an ugly mess.
I cannot even slip a junior hacksaw blade between the bottom of the cap
and the PCB and cut it free cos it's obscured by other components.




+1 for can-opening it to save wear and tear on the board. If you
measure 45 ohms ESR in-circuit, it won't be better by itself.

Cheers

Phil Hobbs

Right I'd hack up the component and pull pin by pin.
I do use a hot air rework station on some rotary switches...
it's faster than all that hacking.

George H.

On Tue, 21 Aug 2018 21:54:12 -0700, stratus46 wrote:

I use a Metcal which is a 40 Watt iron very well controlled but when
removing caps from computer motherboards where there are no thermal
reliefs to the ground plane, NO soldering iron can unsolder it alone.

You're not kidding. My largest iron is 40W/80W switchable. 40W won't
touch it and I'm not risking 80W! The biggest problem seems to be the cap
case - a long 1" dia aluminium tube with 3 tags at the bottom going
straight to PCB grounds. It's acting like a very effective heat sink.
Going to have to trash the caps from above.





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On Tuesday, August 21, 2018 at 7:46:24 PM UTC-4, Cursitor Doom wrote:
I have just spent about 40m trying to unsolder an electro on the board of
the Tek 466 I'm currently working on. It showed a ESR of 45 ohms so I
needed to hook it out of circuit just to be doubly sure it was really
that bad.
The electros in question are all fairly large ones in the (linear) PSU
section. For some reason they've not used separate boards for the various
sub-circuits, so the PSU is just one area of a v.large board which also
has components for all sorts of other functions. Anyway, The cap in
question has 5 connections to the board: 3 equi-spaced ground tabs around
the outside that come straight from the case of the cap and the 2 + and -
wires close to the centre. Given 5 in total through-hole connections,
it's proving very difficult to remove the cap using suction pump and
solder braid cos I cannot wiggle it at all. The best solution IMO would
be to heat all 5 tabs at the same time whilst pulling the cap's case from
the other side until it breaks free. Is there any tool that enables you
to do this? I fear the amount of ****ing around I'm having to do
otherwise will lead to delamination of the PCB traces and an ugly mess.
I cannot even slip a junior hacksaw blade between the bottom of the cap
and the PCB and cut it free cos it's obscured by other components.



You need to preheat the board. BTW, rocking a component while desoldering is a recipe for disaster if the board in question is a multi-layer. An internal foil can be separated from the plated-through hole if physical assertion is used.

If you can't remove the board to put it in a pre-heater, aim a hair dryer at it for about 10-15 minutes (a real heat gun can blister it). When the board is good and hot, it will have far less propensity to sink off heat from your soldering iron tip.

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.

On 08/22/2018 06:12 AM, Cursitor Doom wrote:
On Tue, 21 Aug 2018 21:28:10 -0400, Phil Hobbs wrote:

+1 for can-opening it to save wear and tear on the board. If you
measure 45 ohms ESR in-circuit, it won't be better by itself.

Well, it's hardly surprising for an electro of this age. Clearly the
original component from a scope with a s/n indicating it was manufactured
44 years ago! What was more surprising was that only 2 out of 6 electros
in the PSU section showed abnormal readings (the remaining faulty one has
gone leaky).

I have a Keithley 410 Micro-Microammeter from about 1960 that has all
its original electros and still works fine. Of course it uses an
electrometer tube, so it takes a good couple of hours' warm-up to settle
down on the 100-fA FS range, but it eventually does.

It has way more soul than my 610C(*), but really isn't nearly as good a
meter. (Don't anybody tell it, though--it has an honoured place on my
bench shelf.)

Cheers

Phil Hobbs

(*) "Now Nortons and Indians and Greeveses won't do...They don't have a
soul like a Vincent '52." -- Richard Thompson

--
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

Cursitor Doom prodded the keyboard with:

On Tue, 21 Aug 2018 21:54:12 -0700, stratus46 wrote:

I use a Metcal which is a 40 Watt iron very well controlled but
when removing caps from computer motherboards where there are no
thermal reliefs to the ground plane, NO soldering iron can unsolder
it alone.

You're not kidding. My largest iron is 40W/80W switchable. 40W won't
touch it and I'm not risking 80W! The biggest problem seems to be
the cap case - a long 1" dia aluminium tube with 3 tags at the
bottom going straight to PCB grounds. It's acting like a very
effective heat sink. Going to have to trash the caps from above.

Have you tried making a soldering bit with a piece of split copper
tube and a cooks torch to heat it. Apply to all the pins up at once.

--
Best Regards:
Baron.

Some styles of electrolytics may be particularly difficult to remove gracefully. The ground tabs of the FP style were often twisted for mechanical stability before soldering. And sometimes, the pins were folded over before soldering.

On Friday, 24 August 2018 02:24:43 UTC+1, wrote:

Some styles of electrolytics may be particularly difficult to remove gracefully. The ground tabs of the FP style were often twisted for mechanical stability before soldering. And sometimes, the pins were folded over before soldering.

If enough solder is removed, twisted tabs can then be twisted back. A bit of remaining solder can be ignored, it lacks enough strength to get in the way. Folded over legs can be pushed up with a soldering iron before attempting removal.


NT

On 08/24/2018 04:27 AM, wrote:
On Friday, 24 August 2018 02:24:43 UTC+1, wrote:

Some styles of electrolytics may be particularly difficult to remove gracefully. The ground tabs of the FP style were often twisted for mechanical stability before soldering. And sometimes, the pins were folded over before soldering.

If enough solder is removed, twisted tabs can then be twisted back. A bit of remaining solder can be ignored, it lacks enough strength to get in the way. Folded over legs can be pushed up with a soldering iron before attempting removal.


NT


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.

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

On Fri, 24 Aug 2018 13:18:02 -0400, Phil Hobbs wrote:

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.

I had to use one of these so-called multi-tools to slice through the
pins. There was about 2mm of clearance between the bottom of the caps and
the PCB. This is one of those cutters that vibrates from side to side at
high speed and the blade had *just* enough reach to cut through the most
inaccessible pins. Double checking after removal confirmed they had all
definitely failed (3 out of 6 altogether).





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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?




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On Saturday, 25 August 2018 00:42:23 UTC+1, 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?

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.


NT

In article ,
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 .

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

--
(Please post followups or tech inquiries to the USENET newsgroup)
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MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
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www.flippers.com
"Old pinballers never die, they just flip out."

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


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

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

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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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.

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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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


--
(Please post followups or tech inquiries to the USENET newsgroup)
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MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
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www.flippers.com
"Old pinballers never die, they just flip out."

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.

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.

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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In article , 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.

On 2018/08/27 2:01 AM, wrote:
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.


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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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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In article , 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.

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?

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.

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 **** for a living, and I refuse to waste my
time, or reputation, with any "crack pot" repairs.



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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 **** 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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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