Electrolytic capacitor question

[[email protected]]

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 likethis. 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 capfor 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 mindthat 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

 

[Kripton]

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.
--

 

[Paul Drahn]

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

 

[Geoffrey S. Mendelson]

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]

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.

 

[Phil Allison]

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

 

[Phil Allison]

"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

 

[Geoffrey S. Mendelson]

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.

 

[[email protected]]

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

 

[Phil Allison]

"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.

 

[Phil Allison]

"Jeff Liebermann = demented lunatic"

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 fucking 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 bullshitting, 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 BULLSHIT like
this ?

Did your mother even know who your father was?

My god you are an asshole.


.... Phil

 

[William Sommerwerck]

"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]

They need to turn up the Variac on your

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

Then I guess it does go to 11!