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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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?

Extron has been doing this for years and of course it is the first
part to fail in their units. Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year or so
for the same reason. Technicians and electronic engineers at my work
place can't think of a rational reason why these manufacturers do
this. This is pro gear where reliability is a great concern so it
doesn't seem to be planned failure mode. Thanks. Chuck
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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?

Chuck wrote in
:

Extron has been doing this for years and of course it is the first
part to fail in their units. Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year or so
for the same reason. Technicians and electronic engineers at my work
place can't think of a rational reason why these manufacturers do
this. This is pro gear where reliability is a great concern so it
doesn't seem to be planned failure mode. Thanks. Chuck


IMO,in a proper design,the caps should not be getting hot.
Caps should be sized and rated properly,with a fair amount of excess
capacity,not sized/rated right at the margins.
We have inexpensive thermal imaging available that can identify hot spots
so that they can be corrected before the design is finalized.


--
Jim Yanik
jyanik
at
localnet
dot com
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Default Why do some manufacturers wrap the electrolytic capacitor that getsthe hottest in a switching power supply in shrink wrap?


Chuck wrote:

Extron has been doing this for years and of course it is the first
part to fail in their units. Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year or so
for the same reason. Technicians and electronic engineers at my work
place can't think of a rational reason why these manufacturers do
this. This is pro gear where reliability is a great concern so it
doesn't seem to be planned failure mode. Thanks. Chuck



Then you need all new technicians and engineers. They have to
minimize lead inductance of the capacitors, at high frequncies. Unless
you don't really want to remove the ripple.


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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?

In article ,
Chuck wrote:

Extron has been doing this for years and of course it is the first
part to fail in their units. Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year or so
for the same reason. Technicians and electronic engineers at my work
place can't think of a rational reason why these manufacturers do
this. This is pro gear where reliability is a great concern so it
doesn't seem to be planned failure mode. Thanks. Chuck


I've heard it said:

"When the question is `Why is company X doing seemingly irrational
thing Y in their product design?', the answer is most commonly
`Money',"

Electrolytic capacitors are normally shipped, by their manufacturers,
in a plastic insulating jacket. It's the common method used to
insulate the cases against accidental shorts, and to allow convenient
marking (no separate marking process is required during manufacture,
since the markings are manufactured into the plastic).

Almost all "commodity" 'lytics are of this sort. If you want caps
with another sort of jacketing (even "none at all") you'd probably
have to special-order them, there would be far fewer possible sources,
and the cost per piece would end up being significantly higher.

There's immense price-pressure and competition in the electronics
manufacturing business, even for "pro gear". A matter of a few cents
per power supply can make the difference between a contract
manufacturer getting, or losing the bid. The manufacturers thus have
a *very* strong incentive to use standard parts... and, in fact, the
cheapest and lowest-rated ones which will allow the final supply to
pass its paper requirements (which may not include long-life survival
tests).

I've heard that it's quite common for overseas contract manufacturers
to covertly "down-rate" parts, after they win a bid... that is, the
specific caps and resistors and etc. that they stuff into the
production lots, may not be the same as the ones they stuffed into the
samples that they submitted. Unless you stand over 'em with a club,
and do a strict verification of what you receive, you may get
lower-quality subsystems than you had been originally offered. You
might even get counterfeit parts (e.g. cheap 85-degree-C caps, which
have been falsely labeled as 105-degree-C, or generic caps falsely
marked to indicate low-ESR, high-ripple-current ruggedness).

If the final system survives to the end of its warranty period, many
companies seem to feel that this is Plenty Good Enough, and brings in
additional revenue for repairs and replacements.

--
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Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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boycott any company which has the gall to send me such ads!
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Default Why do some manufacturers wrap the electrolytic capacitor thatgets the hottest in a switching power supply in shrink wrap?

On Aug 30, 2:48*pm, Jim Yanik wrote:
Chuck wrote innews:

:

Extron has been doing this for years and of course it is the

first
part to fail in their units. *Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year

or so
for the same reason. *Technicians and electronic engineers at my

work
place can't think of a rational reason why these manufacturers do
this. *This is pro gear where reliability is a great concern so

it
doesn't seem to be planned failure mode. *Thanks. *Chuck


IMO,in a proper design,the caps should not be getting hot.
Caps should be sized and rated properly,with a fair amount of

excess
capacity,not sized/rated right at the margins.
We have inexpensive thermal imaging available that can identify hot

spots
so that they can be corrected before the design is finalized.

--
Jim Yanik
jyanik
at
localnet
dot com


The caps may not be getting hot on their own but get damaged from
nearby hot items. We had 16 Samsung digital tuners at work that had 1
cap that fails next to a diode on a heatsink. We replaced it with a
very good grade cap but extended the leads just enough to lay the cap
on its side away from the heatsink. Luckily room to do that existed.




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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?


"Chuck"

Extron has been doing this for years and of course it is the first
part to fail in their units. Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year or so
for the same reason.


** What a load of bull**** !!

Putting a shrink wrap sleeve around an electro will not make it fail early.

I bet the sleeve is there for a totally non electronic reason - like being
able to put markings on it with a pen.



..... Phil




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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?

On Tue, 30 Aug 2011 15:47:21 -0500, Chuck wrote:

Extron has been doing this for years and of course it is the first
part to fail in their units. Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year or so
for the same reason. Technicians and electronic engineers at my work
place can't think of a rational reason why these manufacturers do
this. This is pro gear where reliability is a great concern so it
doesn't seem to be planned failure mode. Thanks. Chuck


Probably to keep you from touching the can, which is probably
electrically hot. The life you save may be your own.

Electrolytic caps do not normally get hot. There is a temperature
rise equal to the ripple current times the square of the ESR
(equivlent series resistance). If the ESR is too high, usually due to
underspecifying the voltage rating or capacitor type, it will get
warm. There are derating curves for capacitors at various
temperatures. There are also lifetime prediction calculators which
include the operating temperature.

If you're shopping for a conspiracy theory, I guess the capacitors are
badly specified or picking up heat from adjacent heat dissipating
devices. A nearby resistor or heat sunk xsistor will heat up a cap
quite nicely. The shrink tube will have little effect on the cap
temperature. Black absorbs more heat, so it might be slightly warmer
from nearby radiation. At best, maybe a degree or two.

Pro audio is the same as consumer audio, except for the price tag and
the hype.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
#
http://www.LearnByDestroying.com AE6KS
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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?


"Jeff Liebermann"

Electrolytic caps do not normally get hot. There is a temperature
rise equal to the ripple current times the square of the ESR
(equivlent series resistance).



** Wanna try that again ??


Pro audio is the same as consumer audio, except for the price tag and
the hype.


** Only true of most Chinese made stuff.



..... Phil


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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?

On Wed, 31 Aug 2011 11:14:07 +1000, "Phil Allison"
wrote:

"Jeff Liebermann"

Electrolytic caps do not normally get hot. There is a temperature
rise equal to the ripple current times the square of the ESR
(equivlent series resistance).



** Wanna try that again ??


Oops.
Powah = Ripple Current squared times ESR.
Thanks (grumble)...

Pro audio is the same as consumer audio, except for the price tag and
the hype.


** Only true of most Chinese made stuff.


I didn't know that anything was made outside of China these days. If
the boards and boxes aren't built in China, the components probably
are made in China.
http://www.made-in-china.com/products-search/hot-china-products/Pro_Audio.html
http://www.made-in-china.com/Consumer-Electronics-Catalog/Professional-Audio-Lighting.html
http://www.diytrade.com/china/4/products-list/0-k-c-1/pro_audio.html
http://www.alibaba.com/countrysearch/CN/pro_audio.html




--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
#
http://www.LearnByDestroying.com AE6KS
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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?

Chuck wrote in message
...
Extron has been doing this for years and of course it is the first
part to fail in their units. Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year or so
for the same reason. Technicians and electronic engineers at my work
place can't think of a rational reason why these manufacturers do
this. This is pro gear where reliability is a great concern so it
doesn't seem to be planned failure mode. Thanks. Chuck



Someone's idea of a black body radiator?




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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?

Elevated internal current leakage in electrolytic caps will heat them up.
The 'lytics with higher than normal internal leakage are the ones that
troubleshooters will miss, if the only tester they have is an ESR meter.

Leakage tests aren't performed in-circuit, therefore it's a good practice to
test new 'lytics when they're received and again before installing them if
they've been stored for long periods.

I don't do much repair work anymore, but had a habit of checking ESR (Value
and DA) and Leakage when new caps were received, and some new 'lytics would
fail Leakage tests occasionally, quickly getting very warm at their rated
voltage.

One of the most often repeated repair tips is to look for bulged tops and/or
signs of external leakage wrt electrolytic caps.
Generally, ESR checks are also advised, but electrolytic caps have other
faults and failures which rarely get mentioned.

--
Cheers,
WB
..............


"Jeff Liebermann" wrote in message
...

Probably to keep you from touching the can, which is probably
electrically hot. The life you save may be your own.

Electrolytic caps do not normally get hot. There is a temperature
rise equal to the ripple current times the square of the ESR
(equivlent series resistance). If the ESR is too high, usually due to
underspecifying the voltage rating or capacitor type, it will get
warm. There are derating curves for capacitors at various
temperatures. There are also lifetime prediction calculators which
include the operating temperature.

If you're shopping for a conspiracy theory, I guess the capacitors are
badly specified or picking up heat from adjacent heat dissipating
devices. A nearby resistor or heat sunk xsistor will heat up a cap
quite nicely. The shrink tube will have little effect on the cap
temperature. Black absorbs more heat, so it might be slightly warmer
from nearby radiation. At best, maybe a degree or two.

Pro audio is the same as consumer audio, except for the price tag and
the hype.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
#
http://www.LearnByDestroying.com AE6KS


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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?

On Tue, 30 Aug 2011 15:31:52 -0700, (Dave Platt)
wrote:

In article ,
Chuck wrote:

Extron has been doing this for years and of course it is the first
part to fail in their units. Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year or so
for the same reason. Technicians and electronic engineers at my work
place can't think of a rational reason why these manufacturers do
this. This is pro gear where reliability is a great concern so it
doesn't seem to be planned failure mode. Thanks. Chuck


I've heard it said:

"When the question is `Why is company X doing seemingly irrational
thing Y in their product design?', the answer is most commonly
`Money',"

Electrolytic capacitors are normally shipped, by their manufacturers,
in a plastic insulating jacket. It's the common method used to
insulate the cases against accidental shorts, and to allow convenient
marking (no separate marking process is required during manufacture,
since the markings are manufactured into the plastic).

Almost all "commodity" 'lytics are of this sort. If you want caps
with another sort of jacketing (even "none at all") you'd probably
have to special-order them, there would be far fewer possible sources,
and the cost per piece would end up being significantly higher.

There's immense price-pressure and competition in the electronics
manufacturing business, even for "pro gear". A matter of a few cents
per power supply can make the difference between a contract
manufacturer getting, or losing the bid. The manufacturers thus have
a *very* strong incentive to use standard parts... and, in fact, the
cheapest and lowest-rated ones which will allow the final supply to
pass its paper requirements (which may not include long-life survival
tests).

I've heard that it's quite common for overseas contract manufacturers
to covertly "down-rate" parts, after they win a bid... that is, the
specific caps and resistors and etc. that they stuff into the
production lots, may not be the same as the ones they stuffed into the
samples that they submitted. Unless you stand over 'em with a club,
and do a strict verification of what you receive, you may get
lower-quality subsystems than you had been originally offered. You
might even get counterfeit parts (e.g. cheap 85-degree-C caps, which
have been falsely labeled as 105-degree-C, or generic caps falsely
marked to indicate low-ESR, high-ripple-current ruggedness).

If the final system survives to the end of its warranty period, many
companies seem to feel that this is Plenty Good Enough, and brings in
additional revenue for repairs and replacements.



To clarify, this isn't the standard cap wrapping from the factory.
This is a thick piece of shrink tubing that is put over the
capacitor's normal wrapping and then shunk tightly around the cap like
a blanket. Chuck
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Default Why do some manufacturers wrap the electrolytic capacitor thatgets the hottest in a switching power supply in shrink wrap?

Chuck wrote:
Extron has been doing this for years and of course it is the first
part to fail in their units. Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year or so
for the same reason. Technicians and electronic engineers at my work
place can't think of a rational reason why these manufacturers do
this. This is pro gear where reliability is a great concern so it
doesn't seem to be planned failure mode. Thanks. Chuck



What happens when you complain to Extron? And why - if they don't fix
the problem - do you keep dealing with Extron or Smart Technologies?

A company has to respond properly to design flaws or you change suppliers.

Seems simple to me.

If management says the items are cheaper then point out the downstream
repair costs are more than the few bucks it would cost to get a better
supply and thus a better reputation for reliability in the real world
(as opposed to the costing world).

John :-#)#

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John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
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On Wed, 31 Aug 2011 12:55:07 -0700, John Robertson
wrote:

Chuck wrote:
Extron has been doing this for years and of course it is the first
part to fail in their units. Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year or so
for the same reason. Technicians and electronic engineers at my work
place can't think of a rational reason why these manufacturers do
this. This is pro gear where reliability is a great concern so it
doesn't seem to be planned failure mode. Thanks. Chuck



What happens when you complain to Extron? And why - if they don't fix
the problem - do you keep dealing with Extron or Smart Technologies?

A company has to respond properly to design flaws or you change suppliers.

Seems simple to me.

If management says the items are cheaper then point out the downstream
repair costs are more than the few bucks it would cost to get a better
supply and thus a better reputation for reliability in the real world
(as opposed to the costing world).

John :-#)#



I work for a large university and have no say over what products are
chosen for our various projects. Extron doesn't support outside
repair so we don't have any contact with their service or engineering
departments. The reason we use the Sympodium is because some
professors demand them. Chuck
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On Aug 31, 10:53*am, chuck wrote:
On Tue, 30 Aug 2011 15:31:52 -0700, (Dave Platt)
wrote:





In article ,
Chuck wrote:


Extron has been doing this for years and of course it is the first
part to fail in their units. *Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year or so
for the same reason. *Technicians and electronic engineers at my work
place can't think of a rational reason why these manufacturers do
this. *This is pro gear where reliability is a great concern so it
doesn't seem to be planned failure mode. *Thanks. *Chuck


I've heard it said:


*"When the question is `Why is company X doing seemingly irrational
* thing Y in their product design?', the answer is most commonly
* `Money',"


Electrolytic capacitors are normally shipped, by their manufacturers,
in a plastic insulating jacket. *It's the common method used to
insulate the cases against accidental shorts, and to allow convenient
marking (no separate marking process is required during manufacture,
since the markings are manufactured into the plastic).


Almost all "commodity" 'lytics are of this sort. *If you want caps
with another sort of jacketing (even "none at all") you'd probably
have to special-order them, there would be far fewer possible sources,
and the cost per piece would end up being significantly higher.


There's immense price-pressure and competition in the electronics
manufacturing business, even for "pro gear". *A matter of a few cents
per power supply can make the difference between a contract
manufacturer getting, or losing the bid. *The manufacturers thus have
a *very* strong incentive to use standard parts... and, in fact, the
cheapest and lowest-rated ones which will allow the final supply to
pass its paper requirements (which may not include long-life survival
tests).


I've heard that it's quite common for overseas contract manufacturers
to covertly "down-rate" parts, after they win a bid... that is, the
specific caps and resistors and etc. that they stuff into the
production lots, may not be the same as the ones they stuffed into the
samples that they submitted. *Unless you stand over 'em with a club,
and do a strict verification of what you receive, you may get
lower-quality subsystems than you had been originally offered. *You
might even get counterfeit parts (e.g. cheap 85-degree-C caps, which
have been falsely labeled as 105-degree-C, or generic caps falsely
marked to indicate low-ESR, high-ripple-current ruggedness).


If the final system survives to the end of its warranty period, many
companies seem to feel that this is Plenty Good Enough, and brings in
additional revenue for repairs and replacements.


To clarify, this isn't the standard cap wrapping from the factory.
This is a thick piece of shrink tubing that is put over the
capacitor's normal wrapping and then shunk tightly around the cap like
a blanket. *Chuck- Hide quoted text -

- Show quoted text -


Maybe the case is not at "ground" voltage, so the tubing is to act as
an insulator to prevent shocking anyone working on the eqeuipment.


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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?

En el artículo , chuck
escribió:

To clarify, this isn't the standard cap wrapping from the factory.
This is a thick piece of shrink tubing that is put over the
capacitor's normal wrapping and then shunk tightly around the cap like
a blanket. Chuck


Maybe to prevent reading off the value for replacement? Built-in
obsolescence, in the same way the some makers grind the identifying
marks off the top of ICs?

You say in a later post that Extron don't support outside repair, which
lends weight to that theory.

--
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(='.'=)
(")_(")


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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?


"Mike Tomlinson"

Maybe to prevent reading off the value for replacement?


** Absurd.

The most likely reason is to enhance safety.

The shrink wrap used on electros that run hot is prone to breaking and
exposing the metal outer.

Often, there is enough leakage to this outer to be a shock hazard.

A second layer of high temp wrap is a nice precaution.



.... Phil


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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?

On 2011-09-14 09:31:07 +0200, "Phil Allison" said:


"Mike Tomlinson"

Maybe to prevent reading off the value for replacement?


** Absurd.

The most likely reason is to enhance safety.

The shrink wrap used on electros that run hot is prone to breaking and
exposing the metal outer.

Often, there is enough leakage to this outer to be a shock hazard.

A second layer of high temp wrap is a nice precaution.



... Phil


+1
you can also have shrink wrap around the fuse in a smps
it is to prevent glass breaking in case the fuse breaks...
same for the caps, to prevent leaking and touching high voltage.

--
----------
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the ESR Repository @ http://kripton2035.free.fr/esr-repository.html
the Geiger Repository @ http://kripton2035.free.fr/geiger-repositor.html

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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?

On Tue, 30 Aug 2011 15:47:21 -0500, the renowned Chuck
wrote:

Extron has been doing this for years and of course it is the first
part to fail in their units. Smart Technologies Sympodium power
supplies, that they have contract built in China, fail in a year or so
for the same reason. Technicians and electronic engineers at my work
place can't think of a rational reason why these manufacturers do
this. This is pro gear where reliability is a great concern so it
doesn't seem to be planned failure mode. Thanks. Chuck


How about a photo?

There are two possible reasons that I can think of.
If it's a mains input filter capacitor, then it's likely for safety-
to beef up the very, very thin insulation on the capacitor body, so
they can get through the approvals process.

Otherwise, it could be to bolster mechanical support for the part so
it won't suffer failure form vibration, as an alternative to goop.


Best regards,
Spehro Pefhany
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Default Why do some manufacturers wrap the electrolytic capacitor that gets the hottest in a switching power supply in shrink wrap?

En el artículo , Phil Allison
escribió:

The shrink wrap used on electros that run hot is prone to breaking and
exposing the metal outer.

Often, there is enough leakage to this outer to be a shock hazard.


Unlike the shock hazard that's likely to be present on the adjacent
heatsink?

You're full of ****, Phil.

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(='.'=)
(")_(")


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Default Why do some manufacturers wrap the electrolytic capacitor thatgets the hottest in a switching power supply in shrink wrap?

Usually anything on the hot side could use more insulation. Of course
I mean on the hot side of the mains or line. Imagine an electrolytic
bursting, there will be foil all over the place, conductive foil that
is, or else of course the capacitor would never have worked.

They have to think about catastophic failures and ground faults, so
sometimes if you want to know why they did what they did, so do you.
It is quite possibly a containment issue.

It is still a money matter, if they could save one penny they would,
but they have to figure out how many lawsuits and how much, things
like that. Hey, the drug companies think that way, so sure as hell
electronics companies will as well.

J
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