16 Feb
2004
16 Feb
'04
9:39 a.m.
So here is my question then: if not tantalum, then what?
I've always been told that aluminum electrolytic caps were cheap stuff that
doesn't last and that tantalum caps are much better and (that was the claim)
eternal. So I guess this is wrong. What is the truth then? Is it the other
way around? Or are they both bad? And why are so many people, including on
this list, saying "aluminum electrolytics are cheap crap, use tantalum"?
And what are the *good* caps to use?
MS
16 Feb
16 Feb
10:10 a.m.
On Mon, 16 Feb 2004, Michael Sokolov wrote:
So here is my question then: if not tantalum, then
what?
I've always been told that aluminum electrolytic caps were cheap stuff that
doesn't last and that tantalum caps are much better and (that was the claim)
eternal. So I guess this is wrong. What is the truth then? Is it the other
way around? Or are they both bad? And why are so many people, including on
this list, saying "aluminum electrolytics are cheap crap, use tantalum"?
And what are the *good* caps to use?
MS
Must be something about the period when they were made or the manufacturer,
we've used millions over the years and never had much trouble with them...
Tantalums have lower ESR than (standard aluminum electrolytics) and last
longer (dont dry out), plus they have a wider operating temperature range.
Most aluminum electrolytics stop being capacitors around freezing.
So my with experience with Tantalums has been good, I even have some 50's
vintage ones that work fine (Tantalum foil).
Peter Wallace
Mesa Electronics
17 Feb
17 Feb
12:01 p.m.
I find it interesting that so many tants are dying.
Were the deceased run close to their rated voltage? One word suffices
for increased component life: DERATE!
Stick 100V caps where 16V once lived. It costs more. There you go.
tomj
On Mon, 2004-02-16 at 13:10, Peter C. Wallace wrote:
On Mon, 16 Feb 2004, Michael Sokolov wrote:
So here is my question then: if not tantalum,
then what?
I've always been told that aluminum electrolytic caps were cheap stuff that
doesn't last and that tantalum caps are much better and (that was the claim)
eternal. So I guess this is wrong. What is the truth then? Is it the other
way around? Or are they both bad? And why are so many people, including on
this list, saying "aluminum electrolytics are cheap crap, use tantalum"?
And what are the *good* caps to use?
MS
Must be something about the period when they were made or the manufacturer,
we've used millions over the years and never had much trouble with them...
Tantalums have lower ESR than (standard aluminum electrolytics) and last
longer (dont dry out), plus they have a wider operating temperature range.
Most aluminum electrolytics stop being capacitors around freezing.
So my with experience with Tantalums has been good, I even have some 50's
vintage ones that work fine (Tantalum foil).
Peter Wallace
Mesa Electronics 
16 Feb
16 Feb
11:38 p.m.
On Mon, Feb 16, 2004 at 12:39:12PM -0800, Michael Sokolov wrote:
So here is my question then: if not tantalum, then
what?
Why not tantalum? Take into consideration that nothing is for eternity,
whatever you build in. For this particular application, they are appropriate,
and "The Right Thing"(tm).
I've always been told that aluminum electrolytic
caps were cheap stuff that
doesn't last and that tantalum caps are much better and (that was the claim)
eternal. So I guess this is wrong. What is the truth then? Is it the other
This claim has been wrong all the time, and will be in the future as well.
It is by nothing founded on technical issues (and can't be); it is just
opinion and perhaps techno-religion. Don't expect truth.
But BTW, there has been some technical improvements to electronic components
since the days of the NorthStar. More than 20 years *is* somehow
eternity for certain electronic components. Replace the capacitors in question
with modern low-ESR types *designed especially for use in power supplies*.
This will give you some more years - for that particular kind of failure -
but it certainly won't give you any warranty that the system doesn't suffer
another failure.
way around? Or are they both bad? And why are so
many people, including on
this list, saying "aluminum electrolytics are cheap crap, use tantalum"?
Price shouldn't be an issue for conserving this old stuff. There is
more than the question of aluminum caps vs. tantalum ones - that's why the
manufacturers offer such a large variety of capacitors, and resistors, and
semiconductors.
And what are the *good* caps to use?
Sorry, any recommendation will be useless here, as you might not find the
exact component (and slight variations do matter), and depend on the circuitry,
and the environment. You just touched the area of correct design work of
electrical circuits. If you expect "eternity" you cannot rely on any
cookbook recipe if you have no clue what you do.
Holger
17 Feb
17 Feb
11:59 a.m.
Big, huge, gargantuan, monster arrays of dipped silver mica caps?
Seriously, I think you just have to change them often, eg. decadely.
(That's a perfectly cromulent word.)
I think spacecraft programmers know about this sort of thing, but you
could probably design a power supply that presupposed possible failures
like this, but basically no one but us lunatics care about electronic
objects lasting more than five, never mind 10 or 20 years.
tomj
On Mon, 2004-02-16 at 12:39, Michael Sokolov wrote:
So here is my question then: if not tantalum, then
what?
I've always been told that aluminum electrolytic caps were cheap stuff that
doesn't last and that tantalum caps are much better and (that was the claim)
eternal. So I guess this is wrong. What is the truth then? Is it the other
way around? Or are they both bad? And why are so many people, including on
this list, saying "aluminum electrolytics are cheap crap, use tantalum"?
And what are the *good* caps to use?
MS
11:52 a.m.
>>>> "Tom" == Tom Jennings
<tomj(a)wps.com> writes:
Tom> Big, huge, gargantuan, monster arrays of dipped silver mica
Tom> caps? Seriously, I think you just have to change them often,
Tom> eg. decadely.
Actually, at least in switching power supplies, ceramic capacitors are
now a good option. You can get ceramics of several hundred
microfarad, and they are quite small. More expensive than tantalum, I
expect, but more reliable. And if they do fail, they normally fail
open, not shorted as electrolytics do.
paul
7:19 a.m.
Tom> Big, huge, gargantuan, monster arrays of
dipped silver mica
Tom> caps? Seriously, I think you just have to change them often,
Tom> eg. decadely.
Actually, at least in switching power supplies, ceramic capacitors are
now a good option. You can get ceramics of several hundred
microfarad, and they are quite small. More expensive than tantalum, I
expect, but more reliable. And if they do fail, they normally fail
open, not shorted as electrolytics do.
Not only that, will be found shorted, even leaking like a resistor.
Seen these happen with ceramics. When they leak or intermittently
shorting gets you chasing all over. But many times I stop and stare
at schematics and think, try a area where a component is most likely
is failing. Also even a service mode that lets me disable or adjust
a item was helpful. This usually nails it.
Even a semiconductor stuff is known to leak or make signals
intermittent or constantly jumpy (volts) or jitters (waveforms).
Optical coolants (same stuff as anti-freeze) soaked resistors
(especially flameproof & fusible resistors) resistance went down and
blow the semiconductor IC eg: vertical IC after awhile. Made repair
more diffcult till I found out why.
Cheers,
Wizard (working on TV, projector & monitor for shop).
paul
12:45 p.m.
Big, huge, gargantuan, monster arrays of dipped silver
mica caps?
Seriously, I think you just have to change them often, eg. decadely.
(That's a perfectly cromulent word.)
<Grumble ... google ... online dictionary ....not there .... try
another...oh, great, gotta pay for that one...sigh>
"Decadely" I accept, it makes sense by analogy with "weekly".
But "cromulent"? Communication is not being served. Got a synonym I
can look up?
I think spacecraft programmers know about this sort of
thing, but you
could probably design a power supply that presupposed possible failures
like this, but basically no one but us lunatics care about electronic
objects lasting more than five, never mind 10 or 20 years.
It's not guaranteed, even there. There are spacecraft instruments in
build with single capacitors in a circuit where fail-short means the
instrument can't turn on. Same job could have been done with two
capacitors in series. Then if either fails short, the circuit still
works. (It might exceed its timing spec, but it'll work.) In fact I
have caused that addition to be made in some instruments and power
supplies, but the design engineers don't seem to learn easily. And
there are some I didn't get to review until "too late" in the design
cycle. Sigh.
--
- Mark
210-522-6025, page 888-733-0967
18 Feb
18 Feb
2:39 a.m.
New subject: Smoke on the Horizon... oh s**t! (OT)
Big, huge,
gargantuan, monster arrays of dipped silver mica caps?
Seriously, I think you just have to change them often, eg. decadely.
(That's a perfectly cromulent word.)
<Grumble ... google ... online
dictionary ....not there .... try
another...oh, great, gotta pay for that one...sigh>
"Decadely" I accept, it makes sense by analogy with "weekly".
But "cromulent"? Communication is not being served. Got a synonym I
can look up?
8:10 a.m.
On Tue, 2004-02-17 at 15:45, Mark Tapley wrote:
(But I bet they derate that single cap :-)
>Seriously, I think you just have to change them
often, eg. decadely.
>(That's a perfectly cromulent word.)
"Decadely" I accept, it makes sense by
analogy with "weekly".
But "cromulent"? Communication is not being served. Got a synonym I
can look up?
Sheesh, don't all you people watch THE SIMPSONS? How do you make it
through the week?! cctalk content: it's > 10 yrs old now.
I think
spacecraft programmers know about this sort of thing, but you
could probably design a power supply that presupposed possible failures
like this, but basically no one but us lunatics care about electronic
objects lasting more than five, never mind 10 or 20 years.
It's not guaranteed, even there. There are spacecraft instruments in
build with single capacitors in a circuit where fail-short means the
instrument can't turn on. Same job could have been done with two
capacitors in series. Then if either fails short, the circuit still
works. (It might exceed its timing spec, but it'll work.) In fact I
have caused that addition to be made in some instruments and power
supplies, but the design engineers don't seem to learn easily. And
there are some I didn't get to review until "too late" in the design
cycle. Sigh.
Good trick. Design-for-failure isn't a popular subject in
cost-sensitive, quick-to-market business, but it's fascinating work.
I'm working with 5th-year EE students who don't even know how to make
real-world input protection networks, or do real bypassing, but boy can
they crank out SPICE simulations of CMOS gates. You should see their
solenoid driver designs -- >shudder<. Never heard of inductive power
resistors. Reading the fine print in capacitor specs? Fat chance. We're
all doomed.
8:14 a.m.
On Wed, 18 Feb 2004, Tom Jennings wrote:
[much snippage]
I'm working with 5th-year EE students who
don't even know how to make
real-world input protection networks, or do real bypassing, but boy can
they crank out SPICE simulations of CMOS gates. You should see their
solenoid driver designs -- >shudder<. Never heard of inductive power
resistors. Reading the fine print in capacitor specs? Fat chance. We're
all doomed.
My Ex sent me an interesting article she dug up - basically how
40/50/60 year old analog engineers (who still want to work) are able to
literally write their own ticket - starting salaries are in the $100K (US)
range - entirely because of this syndrome.
It's also interesting that Vietnam seems to be turning out very
competent analog design Gurus - 'Nguyen Tranh, BSEE' translates to "You
got it made, buddy!"
I myself have fielded more than one juicy offer by various Gummint
contractor companies - but I'm happy where I am. Nice to know that the
Original Nerds are finally getting their Just Revenge....
Now where's that damn pocket protector...
Cheers
John (BSEE '71)
8:21 a.m.
On Wed, 2004-02-18 at 14:14, John Lawson wrote:
Now where's that damn pocket protector...
Notes that his is sitting right under his monitor next to the slide
rule. It is filled with drafting pens & pencils for use with the
adjacent flow-chart template.
--
Christopher L McNabb Tel: 540 231 7554
Operating Systems Analyst Email: cmcnabb(a)vt.edu
Virginia Tech ICBM: 37.205622N 80.414595W
GMRS: WPSR255 ARS: N2UX Grid Sq: EM97SD
8:42 a.m.
On 18 Feb 2004, Tom Jennings wrote:
On Tue, 2004-02-17 at 15:45, Mark Tapley wrote:
It's all Southpark on my end. The Simpsons became boring to me about 10
years ago. Futurama is much better.
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
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>Seriously, I think you just have to change
them often, eg. decadely.
>(That's a perfectly cromulent word.)
"Decadely" I accept, it makes sense by
analogy with "weekly".
But "cromulent"? Communication is not being served. Got a synonym I
can look up?
Sheesh, don't all you people watch THE SIMPSONS? How do you make it
through the week?! cctalk content: it's > 10 yrs old now. 
2:38 p.m.
Vintage Computer Festival wrote:
It's all Southpark on my end. The Simpsons became
boring to me about 10
years ago. Futurama is much better.
I don't like satire, so I will stick to Japanese Animation.
Mind You this hobby is almost as expensive as Computers or
Real Electronics.
PS. The Nascom 2's do look nice since home brewing today
means umm ... putting your computer into a neon light
case and running RED HAT LINUX.
7461
days inactive
7463
days old
14 comments
13 participants
participants (13)
-
bfranchuk＠jetnet.ab.ca -
cmcnabb＠4mcnabb.net -
dan_williams＠ntlworld.com -
holger.veit＠ais.fhg.de -
jpero＠sympatico.ca -
jpl15＠panix.com -
mike＠ambientdesign.com -
msokolov＠ivan.Harhan.ORG -
mtapley＠swri.edu -
pcw＠mesanet.com -
pkoning＠equallogic.com -
tomj＠wps.com -
vcf＠siconic.com