They're polymer capacitors (polymer takes place of liquid electrolyte)
and are used selectively in equipment. See the second picture down on
the right, for a typical appearance. They lack pressure relief seams.
After the "capacitor plague", where poorly made (bad pH value) electrolyte
was used to make some capacitors, some motherboard makers sought to "distance
themselves" from electrolytics. The slightly different shape of the
polymer capacitors was a "see, ma, no leaky cans" kinda thing. It
was a visual distinction, intended to fool/convince buyers that
they had nothing to fear. Before that introduction, polymer caps
were already being used on video cards. They were more popular
there. They're probably also a bit more expensive.
In the retail motherboard business, the customers see what's
on the motherboard. You have to market to appearances.
In your TV set, the components are not exposed in the same way.
Marketing consists of "look, thin bezels", or "now with built
in spyware". No mention is made of what corners are cut
in the power supply section. If you look at LCD monitors and
the power board in there, the absolute cheapest manufacturing
is used for the power board (sorta the equivalent of what you'd
find in a $20 ATX PSU).
There is nothing wrong with electrolytic capacitors if they're
made properly. Consequently, just because you find a cap
with a pressure relief pattern embossed in the top of the
cap, is no reason to panic.
It's hard to say whether any scumbag is still making caps
using that stolen/incorrect electrolyte formula.
And as to "why do people continue to do bad things",
it's a calculus. "Will I be executed or put in jail?"
That's the question they have to ask themselves every day.
"22 May 2019 Ozone layer: Banned CFCs traced to China say scientists"
I've repaired many TVs from big manufacturers all with leaking capacitor=
s. It's clear that they all wear out after a while, especially in hot e=
And cost and size is not a problem, they're pretty much the same:
I tried to find the cheapest normal and solid capacitors on Ebay, as an =
example 270uf, 16V:
=A33.94 for normal, =A33.83 for solid, so pretty much the same price.
Sizing also almost equal: 12x9mm vs 12x8mm (the solid ones are slightly =
Stop excessive crosposting...
I suppose cos they can get them el chepo. I also have found toward the end
of the 90s, those little tantalum caps that look like blobs of resin
coloured blue tend to go leaky and damage the rest of the circuit.
Nothing is supposed to last any more.
What's wrong with crossposting? There are 4 groups where people might know the answer. Yes, I could post 4 times seperately, but then people wouldn't see each other's replies.
I've checked both Ebay and Alibaba (where you can buy huge bulk quantities), and the prices are no different.
I've never seen the tantalum ones break.
Were those visibly obviously damaged? It's just I've never seen one fail, and was wondering if I could tell from a visual inspection. The electrolytics have clearly failed when they bulge or burst - I see it all the time in old/cheap motherboards, or inside TVs.
This is copied from the web page of a capacitor company.
Pros of aluminum electrolytic capacitors:
Higher voltage ratings available (up to 600V)
Way cheaper pricing (for the same capacitance and voltage)
Better leakage current behavior than polymer
Pros of polymer electrolytic capacitors:
Lower ESR/higher allowable ripple current
No dry-out behavior (unlike aluminum capacitors)
Higher expected lifetime/load life
And while one biased company claims electrolytics
dry out after 3 years (a made up number), another
company (likely using field statistics for their
own capacitors) finds the time constant is 17 years.
And I would have to conclude that the 17 year number
is likely to be closer to the truth (based on old computers
still in a running state, like my first computer from
1998-1999 or so which still operates just fine).
The Arrhenius effect is for real, and operating even
the best electrolytics at high temperature, doesn't
end well. At the highest allowed temperatures, some
of these electrolytics (by calculation) should only
last for 2000 hours. That's what the curve fit data
for accelerated life testing shows. When I say a
number like 17 years, it would be in an item with
proper and copious cooling. Note that electrolytics
themselves get warm in service, depending on the
ripple current being forced through them. The plastic
sleeve on the outside, does not enhance cooling for
those situations. The capacitors in VCore (on the primary
or secondary side) could be experiencing high ripple currents.
And if any are to fail, those should go first. The
"bulk" decouplers placed near a PCI or PCIe slot,
those aren't under nearly the same stress level.
Temperature, both rated and operating, is a factor. As I understand it a
rating of,say, 7000 hours at 105C means for every 10C lower actual
operating temperature it doubles the lifetime. Operating them at 65C
will give approx 12 years of continuous use.
In a old computer the power supply always had it's own fan keeping the
unit relatively cool. In modern TVs, set top boxes etc the room for a
noisy fan giving a decent air flow is somewhat limited and temperatures
within many boxes are 60C+. Many capacitors in switched mode supplies
also seem to be fitted very close to hot heat-sinks! In my experience
it's usually the power supply capacitors that have an early failure.
Some manufactures will fit capacitors rated at 7,000 hours at 85C so
when operating at 65C the life expectancy is closer to 28,000 hours (3
years continuous use).
There is also a problem with life expectancy from self heating due to
the Equivalent Series Resistance (ESR). For a switched mode supply a
capacitor with a low ESR is required. A decade or so ago I read a
technical report from one of the more respected capacitor manufacturers
(Rubicon I think) where they claimed that they used physically larger
cans/packaging than some of their Korean competitors to ensure lower ESR
figures. I always found that when changing duff electrolytic with Korean
brand names such as SamYoung etc. that the replacements from a variety
of reputable brands were physically larger - usually the same diameter
can but the height of the can was maybe 5mm more.
I've had capacitors fail in a couple of PVRs after a couple of years but
carefully selected replacements lasted close to 10 years.
In article , email@example.com
It is not only the cheep or China parts that fail. I have a couple of
pieces of HP test gear that I bought surplus that the capacitors have
failed in the power supplies. They origionally sold for about $ 50,000
each back in the mid 1990's. I guess that about 20 years is not too bad
for them. Not sure how many hours they may have had on them.
Well there seem to be loads of them about. A 15 amp 13.8V PSU I bought brand new had one fail after only 3 months use. And it was only used to about 5A. It's been happy ever since I put a better one in.