I recently replaced a couple of electrolytics in a flat screen TV for a customer. The caps were in the power supply and were of course rated for 105 degrees C. So this brought to mind a question. Could this possibly be an operating temperature? Or is it a storage temperature? Or perhaps it's an internal temperature? It would seem like it would have to be a very high frequency component to ever cause an electrolytic to ever approach anything like this. Could one of these parts rated as such actually get this hot and remain operational? Would this actually be within prudent design parameters for the device? In theory if the caps are not actually operating at even 85 degrees C then why wouldn't you be able to use a lower rated temperature cap for that application?

It would seem to me that if a piece of equipment were designed to run a capacitor that hot or even at 85 degrees C for whatever reason then in my mind that would certainly constitute a very poor design. I have been repairing TV's for many years and the only capacitors I've ever seen get too hot to touch were bad ones. Could someone please explain this rating to me? Thanks, Lenny

On 2013-06-29 21:08:41 +0200, said:

I recently replaced a couple of electrolytics in a flat screen TV for a cus
tomer. The caps were in the power supply and were of course rated for 105 d
egrees C. So this brought to mind a question. Could this possibly be an ope
rating temperature? Or is it a storage temperature? Or perhaps it's an int
ernal temperature? It would seem like it would have to be a very high frequ
ency component to ever cause an electrolytic to ever approach anything like
this. Could one of these parts rated as such actually get this hot and rem
ain operational? Would this actually be within prudent design parameters fo
r the device? In theory if the caps are not actually operating at even 85 d
egrees C then why wouldn't you be able to use a lower rated temperature cap
for that application?

It would seem to me that if a piece of equipment were designed to run a cap
acitor that hot or even at 85 degrees C for whatever reason then in my mind
that would certainly constitute a very poor design. I have been repairing
TV's for many years and the only capacitors I've ever seen get too hot to
touch were bad ones. Could someone please explain this rating to me? Thanks
, Lenny

105 deg is the maximum operating temperature before the capacitor
starts to dry
and loose capacity.
--
----------
Kripton

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

On 6/29/2013 12:08 PM, wrote:
I recently replaced a couple of electrolytics in a flat screen TV for a customer. The caps were in the power supply and were of course rated for 105 degrees C. So this brought to mind a question. Could this possibly be an operating temperature? Or is it a storage temperature? Or perhaps it's an internal temperature? It would seem like it would have to be a very high frequency component to ever cause an electrolytic to ever approach anything like this. Could one of these parts rated as such actually get this hot and remain operational? Would this actually be within prudent design parameters for the device? In theory if the caps are not actually operating at even 85 degrees C then why wouldn't you be able to use a lower rated temperature cap for that application?

It would seem to me that if a piece of equipment were designed to run a capacitor that hot or even at 85 degrees C for whatever reason then in my mind that would certainly constitute a very poor design. I have been repairing TV's for many years and the only capacitors I've ever seen get too hot to touch were bad ones. Could someone please explain this rating to me? Thanks, Lenny
As the owner of an electronic assembly service, I can help you with
this. It has nothing to do with design and everything to do with price
and availability. The manufacturer may be using the cap in another
product and got a good price for buying 50,000 of them. Or, the lower
temperature cap may have had a long lead time, so, with engineering
approval, the purchaser ordered these so the production line was not
shut down.

We fight engineering all the time when they design a product with
several different sizes of SMT resistors, or several capacitors of the
same value, but different tolerances. This adds quite a bit to the
manufacturing cost because each component has to be ordered and
inventoried and used in a separate feeder on the pick-and-place machine.

When engineered for manufacturing efficiency, a single sized resistor
could do the job for all circuits needing that value and wattage. A
single capacitor with a low tolerance will work in all the other
circuits and cost the same in quantity and need only a single item
order, inventory and p-p feeder.

Paul

Kripton wrote:

105 deg is the maximum operating temperature before the capacitor
starts to dry
and loose capacity.

It is unlikely that a cap in a TV set will reach 105C and fail.

What is more likely is that it will reach 50C, especially if there is dust
blocking the vents and an 105C capacitor has a much better chance of
surviving operating at 50C than a capacitor rated 85C.

There may also be an assumption by the design department that some
capacitor manufacturers lie, and an 105C capacitor is really an 85C or
50C capacitor.

If you are reading this it is likely that you would say "if they lie
about the temperature rating, why would I buy from them?", while an
engineer in China who has to buy from a specific vendor would just
accept it and specify higher temp parts to compensate.


Or they just specify the capacitance and size of the cap and the manufacturer
supplies what they make with the 105C rating having absolutely no
significance at all.

Geoff.


--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379
It's Spring here in Jerusalem!!!

wrote:

I recently replaced a couple of electrolytics in a flat screen TV for a customer. The caps were in the power supply and were of course rated for 105 degrees C. So this brought to mind a question. Could this possibly be an operating temperature? Or is it a storage temperature? Or perhaps it's an internal temperature? It would seem like it would have to be a very high frequency component to ever cause an electrolytic to ever approach anything like this. Could one of these parts rated as such actually get this hot and remain operational? Would this actually be within prudent design parameters for the device? In theory if the caps are not actually operating at even 85 degrees C then why wouldn't you be able to use a lower rated temperature cap for that application?

It would seem to me that if a piece of equipment were designed to run a capacitor that hot or even at 85 degrees C for whatever reason then in my mind that would certainly constitute a very poor design. I have been repairing TV's for many years and the only capacitors I've ever seen get too hot to touch were bad ones. Could someone please explain this rating to me? Thanks, Lenny


It's called 'Derating', or not operating a component right at it's
limits. The more of a margin, the longer it lasts. That 85°C, 105°C or
125°C rating is how hot you can run it for its rated useful life. That
can range from 500 to 25000+ hours, depending on what you want to
spend. Input capacitors in the power supply have high ripple current,
which generates heat. The more heat they have to deal with, the shorter
their lives.

Digikey offers 74,859 different types & brands of electrolytics for a
reason.

http://www.digikey.com/product-search/en/capacitors/aluminum-capacitors/131081?k=capacitor

Pinching pennies reduces reliability, like the several years of crap
computer motherboards that were built with substandard crapacitors.

On Sat, 29 Jun 2013 12:08:41 -0700 (PDT),
wrote:

Could this possibly be an operating temperature? Or is it a storage temperature? Or perhaps it's an internal temperature?

No, No, and no. They're the absolute maximum operating temperature,
at which the maximum safe applied voltage hits zero.

The 85/105C temperatures are actually the "knee" on the derating
curve.
http://www.navsea.navy.mil/nswc/crane/sd18/Pages/Capacitors/CapacitorsDerating.aspx
Aluminum electrolytics are near the bottom. See Fig 13:
http://www.navsea.navy.mil/nswc/crane/sd18/Images1/Capacitors/CapacitorsDerating14b2.gif

The temperature also has a big effect on the life of an electrolytic.
http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx

It would seem like it would have to be a very high frequency component
to ever cause an electrolytic to ever approach anything like this.

Wrong. A capacitor only draws current when the voltage across the
leads changes. The capacitor only dissipated power, and converts it
to heat, when the voltage changes. Pure DC across a capacitor does
nothing to produce heat. The AC voltage change might be nothing more
than a few millivolts of ripple in a switching power supply, but since
the current in such supplies is huge, the heat dissipated is quite
large. Ignoring frequency dependent effects, the power dissipated is:
Power = Ripple_voltage^2 / ESR
or
Power = Ripple_current^2 * ESR
where ESR = equivalent series resistance. For example, the CPU filter
caps are typically 1000uF/6.3V electrolytics (0.12 ohms ESR). With a
current probe, I can usually see at least 4A average ripple current on
the CPU power leads. While trying to keep the voltage constant over
such large current variations, each cap would smoke:
P = 4^2 * 0.12 = 2 watts each.
There are typically about 10 caps in the string, dissipating a total
of 20 watts. That's gonna get hot.

Could one of these parts rated as such actually get this hot and
remain operational?

Sure. I've burnt my fingers on electrolytics and the machine
continues to run. I just replaced an ATX power supply on a server
that was running 24x7. Every cap in the PS had the top blown out by
boiling electrolyte. Yet, the only indication of trouble was that the
speedtest.net performance was erratic. When I finally turned off the
power to look inside, things cooled down. Then it wouldn't turn on
again, so the problem was obvious.

Would this actually be within prudent design parameters for the device?

No. However, there are many design parameters. The one that should
be a concern is the expected lifetime. See the formula at the top of:
http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx
One can easily calculate when the capacitor is going to being giving
problems. If you're designed for a 1 year warranty and a 5 year
target life, it makes no sense to use more expensive parts where the
caps might last 30+ years, when you can save a few pennies making it
blow up just after the warranty expires. (Hint: I always recap with
better or higher voltage caps).

In theory if the caps are not actually operating at even 85 degrees C
then why wouldn't you be able to use a lower rated temperature cap
for that application?

Look at Fig 13 in the URL I cited. At 85C, the maximum working
voltage is zero.

It would seem to me that if a piece of equipment were designed to
run a capacitor that hot or even at 85 degrees C for whatever reason
then in my mind that would certainly constitute a very poor design.

Well, the math is easy enough. What's the highest ambient temperature
you plan to operate the LCD monitor? Looking at various random spec
sheets, it looks like 85C is the common maximum for commodity
monitors. With an 85C capacitor, that means that you have absolutely
no way to make this work, because you can't put any voltage across the
cap. So, we go to 105C caps, which now allows you to self-heat the
capacitors with:
105 - 85 = 20C
rise in temperature. That should work, but only if you also take into
consideration voltage deration and expected lifetime.

I have been repairing TV's for many years and the only capacitors
I've ever seen get too hot to touch were bad ones.

Generally true. You can take an IR thermometer, thermistor probe,
thermocouple, or if you have money, an FLIR thermal imager, and
measure the case temp. Note that the inside temperature is much
hotter. That works, until you try it with CPU filter caps, which are
heated via radiation by the CPU and by the fan via convection.

Could someone please explain this rating to me? Thanks, Lenny

See Fig 13 again.

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

Michael A. Terrell wrote:

Pinching pennies reduces reliability, like the several years of crap
computer motherboards that were built with substandard crapacitors.

They were NOT built with substandard capacitors. They were built with
BAD capacitors. At the time a Japanese company famous for their capacatiors
had a Chinese engineer who was studying their production methods.

Not trusting him, they allowed him to learn everything EXCEPT a preservative
in the electrolyte.

He left the company, went back to Tiawan and helped start a capacitor
company. This company offered significant discounts (I've heard 50%)
over their Japanese competitors so all of the Tiawanese computer companies
started buying from them.

Their products worked flawlessly for about 6 months and then started to
leak and fail. By that time there were millions of computers in the field.

It took several years before the last of these capactitors were used in
production, some companies made consumer goods with 90 day warranties and
were willing to take their chances with capactiors that lasted about
6 months of constant use.

They also found their way into 2005 vintage Apple computers, so it must
have been more pervasive than people thought.


I ran into a conflict in 2002, with a vendor who had supplied 14 computers that
all failed at about the same time. I wanted them to come in over a weekend
and replace them all, they wanted me to ship them one a week until they
were all fixed. Since the vendor was a friend of the CEO's brother in law,
you can guess who won.

Geoff.


--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379
It's Spring here in Jerusalem!!!

On Sat, 29 Jun 2013 14:06:33 -0700, Jeff Liebermann
wrote:

What's the highest ambient temperature
you plan to operate the LCD monitor? Looking at various random spec
sheets, it looks like 85C is the common maximum for commodity
monitors. With an 85C capacitor, that means that you have absolutely
no way to make this work, because you can't put any voltage across the
cap. So, we go to 105C caps, which now allows you to self-heat the
capacitors with:
105 - 85 = 20C
rise in temperature. That should work, but only if you also take into
consideration voltage deration and expected lifetime.

Oops. I goofed. I was looking at storage temperatures. Maximum
operating temp is about 40C. Might as well do it right. See:
http://www.navsea.navy.mil/nswc/crane/sd18/Images1/Capacitors/CapacitorsDerating14b2.gif

Temp at 70% Temp at 40% Temp at 20%
of rated voltage of rated voltage of rated voltage
105C rated 75C 85C 95C
85C rated 55C 65C 75C

An 85C rated cap, with 70% of the rated voltage applied, can run up to
65C with a self-heating rise of:
65C - 40C = 15C
The relationship between watts dissipated internally and temp rise for
electrolytics is different for each package. For small Al caps, I use
about 5C/watt. So, this cap can dissipate internally:
15C / 5C/watt = 3 watts
Now, if we replace that with a 105C rated cap, with 70% of the rated
voltage applied, it can run up to 85C with a self heating rise of:
85C - 40C = 25C
This cap can now burn internally:
25C / 5C/watt = 5 watts
In short, the 105C cap can handle about 60% more ripple current for
the same internal temperature rise and:
(5 / 3)^0.5 = 1.29
or about 29% more ripple voltage than the 85C cap.

There's an example of the math he
http://electrochem.cwru.edu/encycl/misc/c04-appguide.pdf


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

"Geoffrey S. Mendelson" wrote:

Michael A. Terrell wrote:

Pinching pennies reduces reliability, like the several years of crap
computer motherboards that were built with substandard crapacitors.

They were NOT built with substandard capacitors. They were built with
BAD capacitors.


They were still substandard, but for the all too well know industrial
espionage. The companies stuffing the motherboards bought them because
they were the cheapest crap they could find.

"Geoffrey S. Mendelson" wrote:

Kripton wrote:

105 deg is the maximum operating temperature before the capacitor
starts to dry
and loose capacity.

It is unlikely that a cap in a TV set will reach 105C and fail.

What is more likely is that it will reach 50C, especially if there is dust
blocking the vents and an 105C capacitor has a much better chance of
surviving operating at 50C than a capacitor rated 85C.

There may also be an assumption by the design department that some
capacitor manufacturers lie, and an 105C capacitor is really an 85C or
50C capacitor.


Who makes 50°C electrolytics?

I recently replaced a couple of electrolytics in a flat screen
TV for a customer. The caps were in the power supply and
were of course rated for 105 degrees C. So this brought to
mind a question. Could this possibly be an operating
temperature? Or is it a storage temperature?
Or perhaps it's an internal temperature?


** Its the actual temp of the cap itself - so it depends on the ambient
temp and any heat dissipation in the cap due to ripple current. The figure
gives the maximum allowable temp for a rated life in thousands of hours.

See any electro data sheet for the details.


It would seem like it would have to be a very high frequency
component to ever cause an electrolytic to ever approach
anything like this. Could one of these parts rated as such
actually get this hot and remain operational?


** The electros in many valve amp get very hot, especially if sited near the
output valves. Marshall guitar amps are a classic example - I have measured
the surface temp on the large can electros at 85C.

The ripple current in many SMPS is enough to heat electros significantly -
that is why you see fans in them.



..... Phil

"Jeff Liebermann is a radio ham Lunatic "


No, No, and no. They're the absolute maximum operating temperature,
at which the maximum safe applied voltage hits zero.

** Complete crap.

85C, 105C and 125C are max usable temperatures at the rated DC voltage.


Wrong. A capacitor only draws current when the voltage across the
leads changes.

** What about leakage ?


The capacitor only dissipated power, and converts it
to heat, when the voltage changes. Pure DC across a capacitor does
nothing to produce heat.


** What about leakage ??

2mA of leakage times 500 volts = 1 watt.

Dickhead radio ham.


Ignoring frequency dependent effects, the power dissipated is:
Power = Ripple_voltage^2 / ESR
or
Power = Ripple_current^2 * ESR
where ESR = equivalent series resistance. For example, the CPU filter
caps are typically 1000uF/6.3V electrolytics (0.12 ohms ESR). With a
current probe, I can usually see at least 4A average ripple current on
the CPU power leads. While trying to keep the voltage constant over
such large current variations, each cap would smoke:
P = 4^2 * 0.12 = 2 watts each.


** ESR is not a fixed number - it varies dramatically with temperature.

The ESR measured at room temp is typically 5 to 10 times higher than when
the cap at say 80C. Check this out with any electro, an ESR meter and hot
air any time you like - electrolytes become way more conductive when HOT.

This makes nonsense of your calculation.


Look at Fig 13 in the URL I cited. At 85C, the maximum working
voltage is zero.


** Complete crap.

All electros are speced for full voltage at max rated temp.

But at max temp, the rated life is typically only a few thousand hours -
before the electrolyte vanishes.


.... Phil

On Sun, 30 Jun 2013 11:34:29 +1000, "Phil Allison"
wrote:

"Jeff Liebermann

No, No, and no. They're the absolute maximum operating temperature,
at which the maximum safe applied voltage hits zero.

85C, 105C and 125C are max usable temperatures at the rated DC voltage.

http://www.navsea.navy.mil/nswc/crane/sd18/Images1/Capacitors/CapacitorsDerating14b2.gif
Do you see where it says "absolute maximum rating"? Notice the
recommended operating voltage at the absolute maximum rating point for
all 3 caps. It's zero because it's not recommended running the
capacitor at the absolute maximum rating. That also includes
semiconductors, automobiles, and thermionic valves, all of which to
disgusting things when operating at their absolute maximum rating.

Wrong. A capacitor only draws current when the voltage across the
leads changes.

** What about leakage ?

What about it? At the typical computer and solid state LCD monitor
voltages, its negligible. It might a problem in hi voltage caps, as
in your tube stuff, solar power inverters, or in electric vehicles,
but not low voltage computah and LCD panels.

The capacitor only dissipated power, and converts it
to heat, when the voltage changes. Pure DC across a capacitor does
nothing to produce heat.

** What about leakage ??
2mA of leakage times 500 volts = 1 watt.

Show me where I can find 500 volts in an LCD monitor or TV?
Incidentally, todays monitors and TV's use LED backlighting, not CCFL
tubes.

Ignoring frequency dependent effects, the power dissipated is:
Power = Ripple_voltage^2 / ESR
or
Power = Ripple_current^2 * ESR
where ESR = equivalent series resistance. For example, the CPU filter
caps are typically 1000uF/6.3V electrolytics (0.12 ohms ESR). With a
current probe, I can usually see at least 4A average ripple current on
the CPU power leads. While trying to keep the voltage constant over
such large current variations, each cap would smoke:
P = 4^2 * 0.12 = 2 watts each.

** ESR is not a fixed number - it varies dramatically with temperature.

In your world, nothing happens without drama.

The ESR measured at room temp is typically 5 to 10 times higher than when
the cap at say 80C. Check this out with any electro, an ESR meter and hot
air any time you like - electrolytes become way more conductive when HOT.

This makes nonsense of your calculation.

Ummm... yeah. See:
http://www.edn.com/design/components-and-packaging/4396282/Power-Tip--50--Avoid-these-common-aluminum-electrolytic-capacitor-pitfalls
Look at Fig 2 and:
http://urrg.eng.usm.my/index.php?option=com_content&view=article&id=249:l inear-and-switching-power-supply-fundamentals-part-14-&catid=31:articles&Itemid=70
At 25C the ESR of their electrolytic is unity (at 100KHz). When the
temp climbs to 85C, it's 0.3 or 0.4 (as best as I can read the
graphs). That makes the room temp value about 3 or 4 times the ESR at
85C, not your 5 to 10 times value. The internal dissipation change
between room temp and 85C is 1/3. My 2 watts of smoke becomes 0.67
watts.

The problem is that nobody runs electrolytics at 85C. Even with 40C
maximum ambient for the monitor, I doubt if anything gets hotter than
maybe 55C. It might be hotter in a computer, where the caps are
wrapped around a hot CPU, but those are usually polymer caps, not
electrolytics.

My guess(tm) is that designers take advantage of the drop in ESR, and
run the ripple current even higher, thus negating any alleged benefits
to running the caps hot.

The capacitance of an electrolytic increases about 5% from 25C to 85C,
which would reduce the ripple voltage by about the same percentage.
That also helps keep the cap cool, but the effect is not large
compared to the change in ESR with temperature.
(Hint: Always design for the worst case, which always seems to happen
at inconvenient times).

Look at Fig 13 in the URL I cited. At 85C, the maximum working
voltage is zero.

All electros are speced for full voltage at max rated temp.

Nothing is ever specified simultaneously at maximum voltage and
maximum temperature. If you're ever tried to run a semiconductor at
more than one of the maximum ratings at the same time, you will likely
have a pile of smoking silicon. Same with an electrolytic capacitor.
All that the max rating really mean is that you can possibly hit *ONE*
of those ratings, and not destroy the part.

For fun, and when it cools down somewhat, I'll make some boiling water
(for tea) and drop in an electrolytic while measuring the ESR with my
Bob Parker ESR meter. It should be interesting to see if practice
follows theory.

But at max temp, the rated life is typically only a few thousand hours -
before the electrolyte vanishes.

Yep. That's because the rated lifetime of a capacitor is specified at
the rated maximum temperature. At 85C, you'll get about 2000 hrs.
Drop the temp 10C, and the expected life will double.

You can get a fair idea of how it works if you ignore ripple current
heating for now:
http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx
Plugging in:
Rated life = 2000 hrs
Rated max voltage = 6.3 VDC
Operating voltage = 5.0 VDC
Max temp rating = 85 C
Ambient = 40 C
Projected Life = 57,000 hrs = 2,375 days = 6.5 years
which is about what I'm seeing with commodity capacitors in ATX power
supplies. If I add 10C to the ambient for self heating by ripple
current (which was somehow left out of the calculator), I get:
Projected Life = 28,511 hrs = 1,188 days = 3.3 years
which is close to what I see with computers running in a burn-in room.


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

Michael A. Terrell wrote:

They were still substandard, but for the all too well know industrial
espionage. The companies stuffing the motherboards bought them because
they were the cheapest crap they could find.

Ok, a matter of semantics. When I think of substandard I think of
someone selling parts that are not manufactured to spec, for example,
a 50C (yes, I know no one sells them as such) cap labeled 85C.

Or a 33mf capacitor that is really 25mf.

These really were up to standards, they had the correct capacitance
and were properly temperature rated. The failure was due to them being unable
to age, which may be considered a manufacturing error, or a design flaw,
planned obsolecence, or outright fraud.

I guess the standard they failed to perform to was MTBF, but was it specified?

Is there a standard for capacitors? Or is that something you compute based
upon temperature rating, expected operating temperature etc, and there
is no standard at all, beyond your calculations?

Geoff.

--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379
It's Spring here in Jerusalem!!!

"Geoffrey S. Mendelson" wrote:

Michael A. Terrell wrote:

They were still substandard, but for the all too well know industrial
espionage. The companies stuffing the motherboards bought them because
they were the cheapest crap they could find.

Ok, a matter of semantics. When I think of substandard I think of
someone selling parts that are not manufactured to spec, for example,
a 50C (yes, I know no one sells them as such) cap labeled 85C.

Or a 33mf capacitor that is really 25mf.

These really were up to standards, they had the correct capacitance
and were properly temperature rated. The failure was due to them being unable
to age, which may be considered a manufacturing error, or a design flaw,
planned obsolecence, or outright fraud.

I guess the standard they failed to perform to was MTBF, but was it specified?


Only a fool would buy caps without a rated lifetime. In most places,
engineering has to approve components before they can be placed in the
system. An 'Item Master' is generated, which has all the
specifications, and should include a datasheet that was in effect at the
time the part was evaluated. Any company that ignores the approval
process is crooked, or incompetent.

The first step is being placed on the 'AVL', or 'Approved Vendors
Lists'. Then each and every component has to be tested & approved. The
testing will depend on the level the company builds to. I approved some
Hitachi and Bourns parts to replace EOL Motorola & Beckman ten turn pots
with an unacceptable failure rate of over 1% due to a manufacturing flaw
caused by their using undersized 'O-rings'. The Bourns had a zero fail
rate for the thousands we used, per year. I also found and added some
'Capstore' RAM to replace the lithium battery powered 2K * 8 we used.
They were not allowed aboard the shuttle or space station, and early
EEPROM was too flaky for the application. The maximum write cycles
would have given too short of a useful lifetime and it's expensive to
service something in orbit.


Is there a standard for capacitors? Or is that something you compute based
upon temperature rating, expected operating temperature etc, and there
is no standard at all, beyond your calculations?

On Sun, 30 Jun 2013 07:34:04 +0000 (UTC), "Geoffrey S. Mendelson"
wrote:

Michael A. Terrell wrote:

They were still substandard, but for the all too well know industrial
espionage. The companies stuffing the motherboards bought them because
they were the cheapest crap they could find.

Ok, a matter of semantics. When I think of substandard I think of
someone selling parts that are not manufactured to spec, for example,
a 50C (yes, I know no one sells them as such) cap labeled 85C.

Or a 33mf capacitor that is really 25mf.

These really were up to standards, they had the correct capacitance
and were properly temperature rated. The failure was due to them being unable
to age, which may be considered a manufacturing error, or a design flaw,
planned obsolecence, or outright fraud.

I guess the standard they failed to perform to was MTBF, but was it specified?

Is there a standard for capacitors? Or is that something you compute based
upon temperature rating, expected operating temperature etc, and there
is no standard at all, beyond your calculations?

Geoff.
One of the most difficult parametrs to evaluate is life expectancy.
It's trivial to test a lot of caps and determine if they meet
capacity, ESR, and leakage specs. Note that even high end (Panasonic)
caps have a rated life expectancy of less than 10,000 hours at rated
temperature, surge, etc. That's less than 14 months. Calculting a
probable life expectancy at the much lower temperature and surge they
nrmally operate at would be difficult. Still, it is obvious that some
brands (Capxon, Elite Lelon) consistently fail much earlier than
others.

PlainBill

On 06/29/2013 9:40 PM, Jeff Liebermann wrote:
On Sun, 30 Jun 2013 11:34:29 +1000, "Phil Allison"
wrote:

"Jeff Liebermann

No, No, and no. They're the absolute maximum operating temperature,
at which the maximum safe applied voltage hits zero.

85C, 105C and 125C are max usable temperatures at the rated DC voltage.

http://www.navsea.navy.mil/nswc/crane/sd18/Images1/Capacitors/CapacitorsDerating14b2.gif
Do you see where it says "absolute maximum rating"? Notice the
recommended operating voltage at the absolute maximum rating point for
all 3 caps. It's zero because it's not recommended running the
capacitor at the absolute maximum rating. That also includes
semiconductors, automobiles, and thermionic valves, all of which to
disgusting things when operating at their absolute maximum rating.

Wrong. A capacitor only draws current when the voltage across the
leads changes.

** What about leakage ?

What about it? At the typical computer and solid state LCD monitor
voltages, its negligible. It might a problem in hi voltage caps, as
in your tube stuff, solar power inverters, or in electric vehicles,
but not low voltage computah and LCD panels.

The capacitor only dissipated power, and converts it
to heat, when the voltage changes. Pure DC across a capacitor does
nothing to produce heat.

** What about leakage ??
2mA of leakage times 500 volts = 1 watt.

Show me where I can find 500 volts in an LCD monitor or TV?
Incidentally, todays monitors and TV's use LED backlighting, not CCFL
tubes.

Ignoring frequency dependent effects, the power dissipated is:
Power = Ripple_voltage^2 / ESR
or
Power = Ripple_current^2 * ESR
where ESR = equivalent series resistance. For example, the CPU filter
caps are typically 1000uF/6.3V electrolytics (0.12 ohms ESR). With a
current probe, I can usually see at least 4A average ripple current on
the CPU power leads. While trying to keep the voltage constant over
such large current variations, each cap would smoke:
P = 4^2 * 0.12 = 2 watts each.

** ESR is not a fixed number - it varies dramatically with temperature.

In your world, nothing happens without drama.

The ESR measured at room temp is typically 5 to 10 times higher than when
the cap at say 80C. Check this out with any electro, an ESR meter and hot
air any time you like - electrolytes become way more conductive when HOT.

This makes nonsense of your calculation.

Ummm... yeah. See:
http://www.edn.com/design/components-and-packaging/4396282/Power-Tip--50--Avoid-these-common-aluminum-electrolytic-capacitor-pitfalls
Look at Fig 2 and:
http://urrg.eng.usm.my/index.php?option=com_content&view=article&id=249:l inear-and-switching-power-supply-fundamentals-part-14-&catid=31:articles&Itemid=70
At 25C the ESR of their electrolytic is unity (at 100KHz). When the
temp climbs to 85C, it's 0.3 or 0.4 (as best as I can read the
graphs). That makes the room temp value about 3 or 4 times the ESR at
85C, not your 5 to 10 times value. The internal dissipation change
between room temp and 85C is 1/3. My 2 watts of smoke becomes 0.67
watts.

The problem is that nobody runs electrolytics at 85C. Even with 40C
maximum ambient for the monitor, I doubt if anything gets hotter than
maybe 55C. It might be hotter in a computer, where the caps are
wrapped around a hot CPU, but those are usually polymer caps, not
electrolytics.

My guess(tm) is that designers take advantage of the drop in ESR, and
run the ripple current even higher, thus negating any alleged benefits
to running the caps hot.

The capacitance of an electrolytic increases about 5% from 25C to 85C,
which would reduce the ripple voltage by about the same percentage.
That also helps keep the cap cool, but the effect is not large
compared to the change in ESR with temperature.
(Hint: Always design for the worst case, which always seems to happen
at inconvenient times).

Look at Fig 13 in the URL I cited. At 85C, the maximum working
voltage is zero.

All electros are speced for full voltage at max rated temp.

Nothing is ever specified simultaneously at maximum voltage and
maximum temperature. If you're ever tried to run a semiconductor at
more than one of the maximum ratings at the same time, you will likely
have a pile of smoking silicon. Same with an electrolytic capacitor.
All that the max rating really mean is that you can possibly hit *ONE*
of those ratings, and not destroy the part.

For fun, and when it cools down somewhat, I'll make some boiling water
(for tea) and drop in an electrolytic while measuring the ESR with my
Bob Parker ESR meter. It should be interesting to see if practice
follows theory.

But at max temp, the rated life is typically only a few thousand hours -
before the electrolyte vanishes.

Yep. That's because the rated lifetime of a capacitor is specified at
the rated maximum temperature. At 85C, you'll get about 2000 hrs.
Drop the temp 10C, and the expected life will double.

You can get a fair idea of how it works if you ignore ripple current
heating for now:
http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx
Plugging in:
Rated life = 2000 hrs
Rated max voltage = 6.3 VDC
Operating voltage = 5.0 VDC
Max temp rating = 85 C
Ambient = 40 C
Projected Life = 57,000 hrs = 2,375 days = 6.5 years
which is about what I'm seeing with commodity capacitors in ATX power
supplies. If I add 10C to the ambient for self heating by ripple
current (which was somehow left out of the calculator), I get:
Projected Life = 28,511 hrs = 1,188 days = 3.3 years
which is close to what I see with computers running in a burn-in room.



___________________________
/| /| | |
||__|| | Please don't |
/ O O\__ feed |
/ \ the trolls |
/ \ \ |
/ _ \ \ ----------------------
/ |\____\ \ ||
/ | | | |\____/ ||
/ \|_|_|/ | __||
/ / \ |____| ||
/ | | /| | --|
| | |// |____ --|
* _ | |_|_|_| | \-/
*-- _--\ _ \ // |
/ _ \\ _ // | /
* / \_ /- | - | |
* ___ c_c_c_C/ \C_c_c_c____________

http://jni.sdf-eu.org/trolls.html

While Phil may actually know what he is talking about - the way he
presents the information - not to mention the personal attacks, places
him in the troll category and until his manners improve he should
simply be ignored.

I don't read his posts, while I do read yours...

John :-#)#

--
(Please post followups or tech enquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

"Geoffrey S. Mendelson" wrote in message
...
Kripton wrote:

105 deg is the maximum operating temperature before the capacitor
starts to dry
and loose capacity.

It is unlikely that a cap in a TV set will reach 105C and fail.

What temperature do hot melt glue sticks melt at?

Before I got an ESR meter I used to see how hot the electrolytics got while
it was running, the aluminium can isn't isolated so touching them can be
dangerous - the first line check was to see which ones could melt the end of
a glue stick.

wrote in message
...
I recently replaced a couple of electrolytics in a flat screen TV for a
customer. The caps were in the power supply and were of course rated for
105 degrees C. So this brought to mind a question. Could this possibly be
an operating temperature? Or is it a storage temperature? Or perhaps it's
an internal temperature? It would seem like it would have to be a very
high frequency component to ever cause an electrolytic to ever approach
anything like this. Could one of these parts rated as such actually get
this hot and remain operational? Would this actually be within prudent
design parameters for the device? In theory if the caps are not actually
operating at even 85 degrees C then why wouldn't you be able to use a
lower rated temperature cap for that application?

It would seem to me that if a piece of equipment were designed to run a
capacitor that hot or even at 85 degrees C for whatever reason then in my
mind that would certainly constitute a very poor design. I have been
repairing TV's for many years and the only capacitors I've ever seen get
too hot to touch were bad ones. Could someone please explain this rating
to me? Thanks, Lenny

I'd take it to be the maximum recomended operating temperature - exceeding
that significantly reduces its life.

Apart from radiated heat from other components (like power resistors) the
main cause of heating is power dissipated in the apparent internal series
resistance; ESR, ripple current - especially high frequency in a SMPSU
constantly alternates between charging and discharging the "ideal"
capasitor, the current going in and out develops a voltage across the ESR -
AxV=W.

On Tue, 2 Jul 2013 22:20:44 +0100, "Ian Field"
wrote:



"Geoffrey S. Mendelson" wrote in message
...
Kripton wrote:

105 deg is the maximum operating temperature before the capacitor
starts to dry
and loose capacity.

It is unlikely that a cap in a TV set will reach 105C and fail.

What temperature do hot melt glue sticks melt at?

It depends on the composition of the glue stick. About 80C is
typical, although it can anywhere from 66C to 147C depending on
composition.
http://www.applied-adhesives.com/products/hot-melt-adhesives.aspx

Before I got an ESR meter I used to see how hot the electrolytics got while
it was running, the aluminium can isn't isolated so touching them can be
dangerous - the first line check was to see which ones could melt the end of
a glue stick.

Good test, but lousy accuracy unless you "calibrate" your glue stick.
I just use an IR thermometer, or if I want better accuracy, a
thermocouple or thermistor thermometer.

So, has anyone measured the temperature of the capacitors in a tube
type amplifier?

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

"Jeff Liebermann = demented lunatic"


So, has anyone measured the temperature of the capacitors in a tube
type amplifier?


** As if they are all the same ....

Go **** you mother - you pathetic, raving, radio ham idiot.

On Wed, 3 Jul 2013 10:15:13 +1000, "Phil Allison"
wrote:

"Jeff Liebermann = demented lunatic"
So, has anyone measured the temperature of the capacitors in a tube
type amplifier?

** As if they are all the same ....

Of course they're not all the same. I want to see if any of them run
anywhere close to 85C or 105C, as claimed. In particular, the big
aluminum can type capacitors that are often misplaced very close to
the tubes. You may actually be correct but I doubt it since aluminum
makes a very good IR reflector. The caps under the chassis are
probably comparatively cool.

While I have a few minutes waiting for the contact cement repairs on
my tennis shoes to dry, I have a mini-rant. Why am I doing your
calculations for you? You proclaim that leakage current is important,
yet I'm expected to do the calculations? You proclaim the temperature
has an effect on ESR, yet I'm expected to calculate how big an effect.
You drag guitar amps, hi-v caps, and internal leakage, into a
discussion on the OP's LCD TV or monitor, which uses low voltage, low
leakage, low-ESR, and apparently low-life capacitors, while I'm
expected to demonstrate the distinction? If you have a point to make,
please do your own calcs.

Go **** you mother - you pathetic, raving, radio ham idiot.

Are you aware that you're breaking Australian law?
http://reason.com/blog/2010/06/17/australian-state-bans-swearing
If there were a reward, I would probably turn you in to the
authorities.

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

"Jeff Liebermann = demented lunatic"


So, has anyone measured the temperature of the capacitors in a tube
type amplifier?

** As if they are all the same ....

Of course they're not all the same.

** Then you only look at those examples that are relevant.


I want to see if any of them run
anywhere close to 85C or 105C, as claimed.

** Then look at the one that was specifically mentioned.

Cos YOU claimed there were NONE and it was impossible.

" The problem is that nobody runs electrolytics at 85C. "


In particular, the big
aluminum can type capacitors that are often misplaced very close to
the tubes. You may actually be correct but I doubt it since aluminum
makes a very good IR reflector.


** The LCR caps in Marshall 100W heads and combos are sleeved in blue
plastic.

Very few electros are bare aluminium.


The caps under the chassis are probably comparatively cool.


** How the **** would a pig ignorant, stinking radio ham like you know ??

Never seen a tube amp in his whole, stinking life.


You proclaim that leakage current is important,

** You claimed it did not EXIST - you ****ing LIAR !!!!!

" A capacitor only draws current when the voltage across the
leads changes. The capacitor only dissipated power, and converts it
to heat, when the voltage changes. Pure DC across a capacitor does
nothing to produce heat."


You proclaim the temperature
has an effect on ESR, yet I'm expected to calculate how big an effect.

** Another pathetic, stupid, LIE !!

Do the simple test YOU talked about !!!!!

" For fun, and when it cools down somewhat, I'll make some boiling water
(for tea) and drop in an electrolytic while measuring the ESR with my
Bob Parker ESR meter. It should be interesting to see if practice
follows theory."

Did this exact test yesterday with a 56uF, 400V, 105C electro branded "
Jamicon ".

Started out with a reading of 0.66ohms, ended up with a reading under 0.1
ohms.

Exactly like I said previously.

BTW: Bob is an old mate of mine.


yet I'm expected to calculate how big an effect.

** No calc is even possible - you bull****ting, septic asshole.


You drag guitar amps, hi-v caps, and internal leakage,


** As well known counter examples to a whole pile of absolute CRAP you
claimed about electros.

A topic you are MONUMENTALLY WRONG ABOUT !!!
-------------------------------------------------------------------

BTW:

Was it you mother or your father who taught you to LIE and BULL**** like
this ?

Did your mother even know who your father was?

My god you are an asshole.


.... Phil

"Phil Allison" wrote in message
...

"Jeff Liebermann = demented lunatic"


So, has anyone measured the temperature of the capacitors in a tube
type amplifier?

** As if they are all the same ....

Of course they're not all the same.

** Then you only look at those examples that are relevant.


I want to see if any of them run
anywhere close to 85C or 105C, as claimed.

** Then look at the one that was specifically mentioned.

Cos YOU claimed there were NONE and it was impossible.

" The problem is that nobody runs electrolytics at 85C. "


In particular, the big
aluminum can type capacitors that are often misplaced very close to
the tubes. You may actually be correct but I doubt it since aluminum
makes a very good IR reflector.


** The LCR caps in Marshall 100W heads and combos are sleeved in blue
plastic.

Very few electros are bare aluminium.


The caps under the chassis are probably comparatively cool.


** How the **** would a pig ignorant, stinking radio ham like you know ??

Never seen a tube amp in his whole, stinking life.


You proclaim that leakage current is important,

** You claimed it did not EXIST - you ****ing LIAR !!!!!

" A capacitor only draws current when the voltage across the
leads changes. The capacitor only dissipated power, and converts it
to heat, when the voltage changes. Pure DC across a capacitor does
nothing to produce heat."


You proclaim the temperature
has an effect on ESR, yet I'm expected to calculate how big an effect.

** Another pathetic, stupid, LIE !!

Do the simple test YOU talked about !!!!!

" For fun, and when it cools down somewhat, I'll make some boiling water
(for tea) and drop in an electrolytic while measuring the ESR with my
Bob Parker ESR meter. It should be interesting to see if practice
follows theory."

Did this exact test yesterday with a 56uF, 400V, 105C electro branded "
Jamicon ".

Started out with a reading of 0.66ohms, ended up with a reading under 0.1
ohms.

Exactly like I said previously.

BTW: Bob is an old mate of mine.


yet I'm expected to calculate how big an effect.

** No calc is even possible - you bull****ting, septic asshole.


You drag guitar amps, hi-v caps, and internal leakage,


** As well known counter examples to a whole pile of absolute CRAP you
claimed about electros.

A topic you are MONUMENTALLY WRONG ABOUT !!!
-------------------------------------------------------------------

BTW:

Was it you mother or your father who taught you to LIE and BULL****
like this ?

Did your mother even know who your father was?

My god you are an asshole.

They need to turn up the variac on your ECT machine!!!

"Ian Field" wrote in message ...

They need to turn up the variac on your ECT machine!!!

I doubt it goes all the way to 11.

William Sommerwerck wrote:

"Ian Field" wrote in message ...

They need to turn up the variac on your ECT machine!!!

I doubt it goes all the way to 11.


No doubt.

Too bad it doesn't go to 11...cubed!

"William Sommerwerck" wrote in message
...
"Ian Field" wrote in message ...
They need to turn up the variac on your ECT machine!!!

I doubt it goes all the way to 11.

IIRC - most variacs go up to 110%.

They need to turn up the Variac on your
ECT machine!!!

I doubt it goes all the way to 11.

IIRC... Most variacs go up to 110%.

Then I guess it does go to 11!

William Sommerwerck wrote:

They need to turn up the Variac on your
ECT machine!!!

I doubt it goes all the way to 11.

IIRC... Most variacs go up to 110%.

Then I guess it does go to 11!


All I've seen are either 1:1 at maximum, or 6:7 (120 In/140 Out) if
they have the over voltage output tap.

"Michael A. Terrell" wrote in message
m...

William Sommerwerck wrote:

They need to turn up the Variac on your
ECT machine!!!

I doubt it goes all the way to 11.

IIRC... Most variacs go up to 110%.

Then I guess it does go to 11!


All I've seen are either 1:1 at maximum, or 6:7 (120 In/140 Out) if
they have the over voltage output tap.

The ones I've seen here in the UK have a reversible dial plate screwed to
the back of the knob - one side is calibrated in %, turn it over and its
marked in volts.

All I've seen so far had a few more turns past the live input terminal so
you could select a higher voltage than was going in, my variac is gathering
cobwebs in the garage somewhere, so its not easy to check the exact % over
Vin.

On Thu, 4 Jul 2013 18:14:26 +0100, "Ian Field"
wrote:

All I've seen so far had a few more turns past the live input terminal so
you could select a higher voltage than was going in, my variac is gathering
cobwebs in the garage somewhere, so its not easy to check the exact % over
Vin.

This might help:
http://www.ineedcoffee.com/08/hottop-roaster/images/variac500.jpg
The scale usually says 0-100, but at 100, it's well over the input
voltage. The better variacs have voltages marked on the scale. I
have several and will dig one out later for a fast test.

Mo
http://www.youtube.com/watch?v=ixKNrLjv91Y
Note the printed scale at the beginning of the video.



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

In article ,
Michael A. Terrell wrote:

I doubt it goes all the way to 11.
IIRC... Most variacs go up to 110%.
Then I guess it does go to 11!

All I've seen are either 1:1 at maximum, or 6:7 (120 In/140 Out) if
they have the over voltage output tap.

Is that the one marked "Spinal"?

--
--------------------------------------+------------------------------------
Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk

--- news://freenews.netfront.net/ - complaints: ---

"Mike" wrote in message
...
In article ,
Michael A. Terrell wrote:

I doubt it goes all the way to 11.
IIRC... Most variacs go up to 110%.
Then I guess it does go to 11!

All I've seen are either 1:1 at maximum, or 6:7 (120 In/140 Out) if
they have the over voltage output tap.

Is that the one marked "Spinal"?

They'd just got back from a gig in "Hungaria" when they were in the
Simpsons.