Bad cap topologies

[William Sommerwerck]

Don't be silly. Products with an unacceptable failure rate simply won't
sell. Especially components where there are alternative suppliers.

So how does the Chinese company Lifetime stay in business?

 

[Geoffrey S. Mendelson]

Dave Plowman (News) wrote:

Don't be silly. Products with an unacceptable failure rate simply won't
sell. Especially components where there are alternative suppliers.

If only that were true. People often buy based soley upon price. Rarely
do you see the same product sold for more than a month or two, often
the replacement product has a different brand name.

Since you are in the UK look at the 10 quid DVD players ASDA sold a few
years ago. How many of them are still around? When they fail, how many people
go as far as buying a "cleaning disk" and using it instead of just throwing
it out?

I know we have different experience with cleaning disks, but it's a
positive action by a consumer to resolve the problem themselves instead
of just dumping it in the bin, no matter if it works or not, or does more
harm than good.

Here they go for between 100-150 NIS (16-24 UKP) due to taxes and overhead.
Now that we have entered the "digital age", people are replacing them with
"full HD" players that do image upscaling (aka faking it) which sell for
around 60 UKP.

With those prices it does not pay to make the trip to a repair shop and
certainly not to pay for a repair.

Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM

 

[Dave Plowman (News)]

In article <slrnh8kvst.2d6.gsm@cable.mendelson.com>,
Geoffrey S. Mendelson <gsm@mendelson.com> wrote:

Don't be silly. Products with an unacceptable failure rate simply won't
sell. Especially components where there are alternative suppliers.

If only that were true. People often buy based soley upon price. Rarely
do you see the same product sold for more than a month or two, often
the replacement product has a different brand name.

But those buying components for a manufacturer ain't 'people'. They will
expect only a tiny number of failures from that component - anything else
would be a nonsense. Given the number of different components in the
average piece of consumer electronics. Which means the component makers
must have decent quality control.

Since you are in the UK look at the 10 quid DVD players ASDA sold a few
years ago. How many of them are still around? When they fail, how many
people go as far as buying a "cleaning disk" and using it instead of
just throwing it out?

Dunno. Cheap electronics from the major UK supermarkets ain't worth
having. Go to Lidl or Aldi for such things - they are miles better. The
Germans obviously expect more.

I know we have different experience with cleaning disks, but it's a
positive action by a consumer to resolve the problem themselves instead
of just dumping it in the bin, no matter if it works or not, or does more
harm than good.

Here they go for between 100-150 NIS (16-24 UKP) due to taxes and
overhead. Now that we have entered the "digital age", people are
replacing them with "full HD" players that do image upscaling (aka
faking it) which sell for around 60 UKP.

With those prices it does not pay to make the trip to a repair shop and
certainly not to pay for a repair.

Labour rates mean repairing many consumer goods ain't worth it,
commerically. And, of course SM components. ;-)

--
*No sentence fragments *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[Geoffrey S. Mendelson]

William Sommerwerck wrote:

Don't be silly. Products with an unacceptable failure rate simply won't
sell. Especially components where there are alternative suppliers.

So how does the Chinese company Lifetime stay in business?

Many Chinese component manufacturers don't sell to outside of China. The
companies that buy from them build a production run of a product and then
stop. They then move one to the next product. By the time they show up on
your shelf, it may be 3-6 months since they were produced, and several models
ago.

The manufacturer simply does not care, they don't take warranty returns. If the
unit price of a product is $50 and 1% are expected to fail, they sell the for
$48 (in reality they price them at $52 and sell them for $50). It's up to the
importer in your country to deal with returns.

In the case of large companies, they don't bother. A returned item is replaced
with a new (and probably later) one, and the old one gets thrown out or
recycled.

Small retailers do the same thing via their distributer or just trash them
depending upon the contract they have.

None of the units ever make it back to China, except in containers of recycled
goods for dumping.

This is nothing new, about 25 years ago I was very friendly with the number
one importer of "220" or "grey" goods on the east coast of the US. He would
take defective stuff back for repair, but could never keep a tech at what he
could afford to pay them. In the end the stuff just ended up in the trash and
the prices were raised enough to cover the losses.

I also read news stories in the past where major US retailers were keeping track
of people who returned goods and if you returned too many, they would not let
you return any more.

One US manufacturer of radios has a 30 day return for refund policy, but
won't sell you another radio if you return one.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com N3OWJ/4X1GM

 

[Wild_Bill]

Although I neglected to make it clear, I was commenting on the lack of
quality control in production of finished electronic gear, namely consumer
electronic gear.

For medical or avionics equipment there are very likely to be numerous
levels of quality control, from testing of incoming components to rigorous
testing of the finished products.

For portable CD players that retail for less than $10, I seriously doubt
that any QC exists.
The components are most likely selected/chosen as whatever is cheapest/on
sale that week.

Many manufacturers are thinking in terms of the Harbor Freight business
model. The products are built at the cheapest price point, and the ones that
fail soon (or fail to work) are cheerfully replaced with another one.
The failed units get sold off in bulk to someone else who might try to
salvage/refurbish a number of working products from the failed ones, and/or
just separate the materials and sell them as scrap.

As someone else mentioned, when a product fails prematurely, the consumer
may choose another brand for the next purchase, which very likely could have
been made by the same manufacturer, but with a different brand name on it.

The last time I looked, the supply of refurbished equipment was ample, but
there are no profits to be made from refurbing those $10 CD players. They're
just filler for the landfills, like so many other consumer goods produced
presently.

Refurbishing is relatively expensive due to transportation costs, repairing,
repackaging and redistribution.

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


"Dave Plowman (News)" <dave@davenoise.co.uk> wrote in message
news:508cb0a677dave@davenoise.co.uk...

In article <grnim.552835$6p1.258480@en-nntp-02.dc1.easynews.com>,
Wild_Bill <wb_wildbill@XSPAMyahoo.com> wrote:
not many operate in this way, with very little or no quality control
built into their production facilities.

Don't be silly. Products with an unacceptable failure rate simply won't
sell. Especially components where there are alternative suppliers.

--
*Never underestimate the power of stupid people in large groups.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

On Mon, 17 Aug 2009 12:16:47 -0700, D Yuniskis
<not.going.to.be@seen.com> wrote:

Hi PlainBill,

PlainBill47@yahoo.com wrote:
On Mon, 17 Aug 2009 06:22:49 -0700, D Yuniskis
not.going.to.be@seen.com> wrote:

[much elided]

What I would like to know is which circuit topologies
tend to aggravate this problem. From my casual
observations (I've done most of my repairs without
the benefit of any design documentation), the failing
components either seem to be proximate to heat sources
*or* in configurations where they see high ripple
currents (suggesting this is a problem with the
devices' ESR -- internal heating).

Does anyone have any *definitive* answers about this?
And, long-term remedies? (i.e., does replacement with
a good, high temp, low ESR cap *solve* the problem or
just kick it down the road?)

Are there lessons to be learned when *designing* these
types of circuit topologies to avoid these failure
modes? (besides picking good vendors)

There are a number of factors involved.
1. Poor quality capacitors.

Yes, as I mentioned in my original post. But, my question
is intended to address the *expected* results if "good"
quality capacitors are used in the same circuit topologies.
I.e., will they also exhibit similar failure modes -- just
further down the road? (i.e., what is it about the topology
that causes the failures)

2. High surge currents found in SMPS and the backlight inverter

I.e., caps that handle the large ripple currents.

3. Proximity to heat producing components, chiefly heat sinks

Yes, but this doesn't seem to be as reliable a predictor of
failure. Often there are caps literally *touching* parts
that run VERY hot; yet they don't appear to fail as often
as other parts "free standing" (i.e., nothing within an inch!)
elsewhere in the circuit.

4. Poor ventilation of the electronics portion of the monitor.

Again, that would tend to affect every component in the
circuit (roughly) equally. No doubt it is a contributing
factor -- no doubt alol of the above are contributing
factors!

Because of the current manufacturing / distribution pattern, there is
limited feedback from consumer to designer. Still, the designs of LCD
monitors continue to evolve. A few years ago a 5V 4A power supply was
common. Today the 5V supply is less than half that. The monitor
logic card is being integrated into the LCD panel electronics, further
reducing component count and cost, and improving reliability. With
LED based backlight systems power demands will drop further.

As far as existing monitors, my recommendation is to replace all caps
(except the 150 ľF 450 Volt one) with good brand low ESR parts. My
personal preference is Panasonic FM and FC series', but others have
equivalent success with Rubycon and Nichicon.

I've been using the Panny parts as (historically) they have been
"very good to me" :> But, I ownder if I am just buying a little
more time before similar failures remanifest.

And, as a *designer*, I am interested in determining the real
cause of the problem(s) to ensure that I don't repeat these
problems in my own designs...
It depends on your definition of 'a little time'. My primary source

of information is www.badcaps.net/forum It would appear you are at
least doubling the MTBF (mean time between failures) by using high
quality caps. That would mean if you replace the caps in a two year
old monitor, it will probably last an additional 4 years before it is
necessary to replace them again. At worst, that is a significant
improvement.

When I look at the cost, power consumption, clarity, and design of 4
year old LCD monitors vrs those one or two years old, I doubt that in
5 years you would be asked to repair many 7 year old monitors.

I would agree, having to redo the replacement every two years could
cause speculation about your skills.

PlainBill

 

[D Yuniskis]

Hi PlainBill,

PlainBill47@yahoo.com wrote:

On Mon, 17 Aug 2009 12:16:47 -0700, D Yuniskis

[snip]

Does anyone have any *definitive* answers about this?
And, long-term remedies? (i.e., does replacement with
a good, high temp, low ESR cap *solve* the problem or
just kick it down the road?)

[snip]

And, as a *designer*, I am interested in determining the real
cause of the problem(s) to ensure that I don't repeat these
problems in my own designs...

It depends on your definition of 'a little time'. My primary source
of information is www.badcaps.net/forum It would appear you are at
least doubling the MTBF (mean time between failures) by using high
quality caps. That would mean if you replace the caps in a two year
old monitor, it will probably last an additional 4 years before it is
necessary to replace them again. At worst, that is a significant
improvement.

Agreed. Though, perhaps another way of combining my questions
would be: "Would a different design approach result in a
(much) longer life expectancy for this type of product?"

When I look at the cost, power consumption, clarity, and design of 4
year old LCD monitors vrs those one or two years old, I doubt that in
5 years you would be asked to repair many 7 year old monitors.

Most of the monitors I've been repairing are in the 2-3 year
old range. It's possible that older monitors have already
made their way to The Great Recycling Bin in the Sky. :-/

I would agree, having to redo the replacement every two years could
cause speculation about your skills.

I don't have a fragile ego! :> Rather, I am concerned as to
whether or not I am doing these people (read original post:
"a local non-profit") a *real* service or just buying them
"a little time". I.e., when I am no longer affiliated with
them -- and there is a high probability that they won't have
someone with my skillset available -- will they just see this
whole pattern repeat itself N months/years hence?

And, from a selfish perspective, what can *I* learn from these
failures to help me design products that don't exhibit them!

 

[Dave Plowman (News)]

In article <ogGim.553516$6p1.278767@en-nntp-02.dc1.easynews.com>,
Wild_Bill <wb_wildbill@XSPAMyahoo.com> wrote:

lthough I neglected to make it clear, I was commenting on the lack of
quality control in production of finished electronic gear, namely
consumer electronic gear.

Oh there I'd agree. It is cheaper simply to replace faulty units than test
each and every one fully before dispatch. However there will still be
quality control as no profit will be made if the failure rate is too high.
But that quality control could well consist of just insisting the
component parts are to a standard.

--
*Sorry, I don't date outside my species.

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

On Tue, 18 Aug 2009 21:23:23 -0700, D Yuniskis
<not.going.to.be@seen.com> wrote:

Hi PlainBill,

PlainBill47@yahoo.com wrote:
On Mon, 17 Aug 2009 12:16:47 -0700, D Yuniskis

[snip]

Does anyone have any *definitive* answers about this?
And, long-term remedies? (i.e., does replacement with
a good, high temp, low ESR cap *solve* the problem or
just kick it down the road?)

[snip]

And, as a *designer*, I am interested in determining the real
cause of the problem(s) to ensure that I don't repeat these
problems in my own designs...

It depends on your definition of 'a little time'. My primary source
of information is www.badcaps.net/forum It would appear you are at
least doubling the MTBF (mean time between failures) by using high
quality caps. That would mean if you replace the caps in a two year
old monitor, it will probably last an additional 4 years before it is
necessary to replace them again. At worst, that is a significant
improvement.

Agreed. Though, perhaps another way of combining my questions
would be: "Would a different design approach result in a
(much) longer life expectancy for this type of product?"

When I look at the cost, power consumption, clarity, and design of 4
year old LCD monitors vrs those one or two years old, I doubt that in
5 years you would be asked to repair many 7 year old monitors.

Most of the monitors I've been repairing are in the 2-3 year
old range. It's possible that older monitors have already
made their way to The Great Recycling Bin in the Sky. :-/

I would agree, having to redo the replacement every two years could
cause speculation about your skills.

I don't have a fragile ego! :> Rather, I am concerned as to
whether or not I am doing these people (read original post:
"a local non-profit") a *real* service or just buying them
"a little time". I.e., when I am no longer affiliated with
them -- and there is a high probability that they won't have
someone with my skillset available -- will they just see this
whole pattern repeat itself N months/years hence?

And, from a selfish perspective, what can *I* learn from these
failures to help me design products that don't exhibit them!

Most power supplies I see already use inductors in the DC filters.
You are dealing with a trade off between the switching frequency,
transformer size, and capacitance. That usually results in a 'choose
two of the above' situation.

The only possible change that I am aware of is to use replacements
that have a polymer electrolyte. Frankly, you would be in a better
position to determine if that would be cost effective.

The discussion at badcaps indicates you can expect at least double the
life by using top grade caps. If you are repairing monitors 2-3 years
old, you can expect they will last 4-6 years more after the repair.
Assuming you would be still available to do your excellent repair
work, by that time I would expect a new equivalent monitor would cost
as much as repairing the existing monitor. At that point, repair is
pointless.

PlainBill

 

[whit3rd]

On Aug 18, 5:27 pm, PlainBil...@yahoo.com wrote:

...  My primary source
of information iswww.badcaps.net/forum It would appear you are at
least doubling the MTBF (mean time between failures) by using high
quality caps.

Logically, that should be "at most doubling the MTBF"; remember that
failures can include leaking of corrosive goo and short-circuiting.

It's not surprising that 'badcaps.net' overemphasizes capacitor
quality issues, but my ire is drawn rather to the mechanical design
decisions that put the tiniest available capacitors onto a circuit
board
with zero clearance to adjacent components. An old design
criterion was 'one amp ripple current to one square inch of surface
area' for the purpose of dissipating the inevitable heat buildup.

Empty space is GOOD. Don't minimize it!

To get extra operational margins, it's useful to go to the next larger
size of capacitor (in the case of tight-packed capacitors, that has
to
be longer case sizes, because bigger diameters won't fit). In
theory,
capacitors (like semiconductors and inductors) can benefit from
heatsinking. Has anyone tried it?