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Electrolytic capacitor question

Discussion in 'Electronic Repair' started by [email protected], Jun 29, 2013.

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  1. Guest

    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
     
  2. Kripton

    Kripton Guest

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

    Paul Drahn Guest

    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
     
  4. 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.
     
  5. 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.
     
  6. Phil Allison

    Phil Allison Guest


    ** 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.


    ** 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
     
  7. Phil Allison

    Phil Allison Guest

    "Jeff Liebermann is a radio ham Lunatic "
    ** Complete crap.

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

    ** What about leakage ?


    ** What about leakage ??

    2mA of leakage times 500 volts = 1 watt.

    Dickhead radio ham.


    ** 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.


    ** 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
     
  8. 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.
     
  9. Guest

    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
     
  10. Phil Allison

    Phil Allison Guest

    "Jeff Liebermann = demented lunatic"


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

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

    Phil Allison Guest

    "Jeff Liebermann = demented lunatic"
    ** Then you only look at those examples that are relevant.

    ** 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. "


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

    Very few electros are bare aluminium.


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

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

    ** 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."

    ** 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.

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


    ** 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
     
  12. "Ian Field" wrote in message
    I doubt it goes all the way to 11.
     
  13. They need to turn up the Variac on your
    Then I guess it does go to 11!
     
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