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legg
Guest
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 Posted:
Tue Dec 21, 2004 1:38 am Post subject:
Re: 2200uF 60V tantalum capacitors |
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On Mon, 20 Dec 2004 14:34:27 GMT, Al <no.spam@wanted.com> wrote:
| Quote: | In article <umcbs05d07sfh6ml95lbprudlaak107iio@4ax.com>,
legg <legg@nospam.magma.ca> wrote:
On Sun, 19 Dec 2004 03:19:28 -0600, "Tim Williams"
tmoranwms@charter.net> wrote:
"legg" <legg@nospam.magma.ca> wrote in message
news:gl8as05ku905qt47q07ioerrthfvnpjguf@4ax.com...
Others may have other ideas where to stick them.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3861637697
Wow, that's a neat bit of black box...
Too bad tantalums are notorious for making messes...
I think the 'notorious' problems involved either non-hermetically
sealed parts, copper casings, or oversress / reverse stress of solid
types.
These ain't broke, but obviously could be killed if the user tried
hard enough,
Cheap tantalums do have reliability problems. I have worked in failure
analysis on military electronics for over 30 years and can tell you that
the number of electrically defective tantalums that I have come upon can
be counted on the fingers of one hand. And most of those were the ones
which used sulfuric acid as the electrolyte. A qualified production
line, burn-in and testing will insure trouble free operation for many
years.
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The switch to silver casings and hermetic glass-to-metal seals
addressed the problem with the electrolyte used in wet tantalums. The
later use of tantalum casings was apparently a belt-plus-braces
solution - the improved part types needed requalification, anyways, so
why not.......
All the wet ones I've seen fail, used rubber/plastic/epoxy types of
seals, or plated copper casings.
I inspected the guts of one assembly, in order to get a better idea of
what kind of aminal was being dealt with. No sign of corrosion,
oxidation, pitting, fatigue or leakage anywhere. It was a pain, but it
had to be done before their usefulness could be established to any
extent. Testing only tells you so much about a black box.
RL
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legg
Guest
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| Posted:
Sun Dec 26, 2004 8:23 am Post subject:
Re: 2200uF 60V tantalum capacitors |
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On Sun, 19 Dec 2004 06:48:53 GMT, legg <legg@nospam.magma.ca> wrote:
| Quote: |
One of the last stumbling blocks in getting simpler power supplies to
operate over a wide environmental range, is the capacitors.
Using tantalums gets predictable performance.
There are not too many places where the application pays - designers
tend to work their way around the problem, using other methods.
Others may have other ideas where to stick them.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3861637697
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Well, for whatever the reasons, it seems there are no bidders for such
critters.
http://makeashorterlink.com/?C41956A1A
RL |
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Gregg
Guest
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| Posted:
Sun Dec 26, 2004 3:19 pm Post subject:
Re: 2200uF 60V tantalum capacitors |
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Behold, legg signalled from keyed 4-1000A filament:
I see.
I would think they'd make great SS amp supply filters.
*rubs chin*
--
Gregg t3h g33k
"Ratings are for transistors....tubes have guidelines"
http://geek.scorpiorising.ca |
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Dwaine Garden
Guest
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| Posted:
Mon Dec 27, 2004 1:40 pm Post subject:
Re: 2200uF 60V tantalum capacitors |
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legg wrote:
| Quote: | On Sun, 19 Dec 2004 11:21:25 -0800, mike <spamme0@netscape.net> wrote:
There's a general trend toward INFLATED shipping charges on EBAY. I
suspect that fee avoidance is a part of it. Some openly admit to
padding their profit. Some buyers seem to lose sight of the total cost
and just bid the price up anyway, so it works.
A shipping charge >3X what might be considered reasonable and 40X the
opening bid is a RED flag. Deception in one area is a good indicator of
deception in other areas.
I have no information either way about this poster; just speaking generally.
The format provided by e-bay makes it difficult to enter an advert
without filling in a 'fixed' shiping cost, if origin is non-US. I
suppose there are ways to smooth it out, but I have no experience with
the format.
My research for insured, registered postal service to Australia gave
me a Cdn$80 figure; to UK it was Cdn$50. Obviously a customer would
likely choose a slower verion, at reduced expense, if he had some
confidence in the supplier and was in no great rush. Shipping to US is
likely less, but quoting a low 'fixed' rate could obviously create
problems for the supplier.
I personally prefer standard surface parcel post, which is quite
inexpensive, when purchasing. Strangely, some suppliers won't do it
that way.
While I'm on the soapbox...
There's also another interesting trend. Outright lying about the
product, either by comission or omission. Let the auction end then
disclose the problem. Buyers seem to just pay the inflated price
anyway. Most of what I've been involved with has to do with
missing or broken "accessory items" that are absolutely necessary to get
it to work.
I get annoyed when I lose the opportunity to buy a junker
at a junker price.
Though I haven't bought through e-bay for some years, I've always been
suspicious when bid limits were reached but not exceeded - suggesting
that someone had a method to probe your limit and get you to pay it,
without exposing themselves to the same risk.
It's easier to figure out how a last minute bid can beat you by a
piddling amount - just takes a well-synchronized clock.
Generally it's too expensive to buy junk this way - but lack of other
opportunities, andsome luck can nudge ebay's usefulness upwards, for
many.
RL
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I found my Dynaco ST70 on ebay for $102.00. It was a great find.
Dwaine. |
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legg
Guest
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| Posted:
Mon Dec 27, 2004 4:36 pm Post subject:
Re: 2200uF 60V tantalum capacitors |
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On Sun, 26 Dec 2004 10:19:50 GMT, Gregg <nospam@unknown.org> wrote:
| Quote: | Behold, legg signalled from keyed 4-1000A filament:
Well, for whatever the reasons, it seems there are no bidders for such
critters.
http://makeashorterlink.com/?C41956A1A
I see.
I would think they'd make great SS amp supply filters.
*rubs chin*
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Do you suppose offering four, might make that a more attractive idea?
I'd expected to see at least one bright spark in the audio fringe
pondering the possibility of an aluminium-free circuit.
All I was trying to do was turn a few of these into cash for an
'authentic' replacement part, needed in a 40yr old amp's repair. The
required 40,000uf (3"x3.9") parts don't grow on trees, and I'd never
bother to acquire any on spec, as they die 'on the shelf', unlike the
tantalums described.
ho hum.
RL |
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James Meyer
Guest
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| Posted:
Mon Dec 27, 2004 5:52 pm Post subject:
Re: 2200uF 60V tantalum capacitors |
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On Mon, 27 Dec 2004 03:40:04 -0500, Dwaine Garden <DwaineGarden@rogers.com>
wroth:
| Quote: |
I found my Dynaco ST70 on ebay for $102.00. It was a great find.
Dwaine.
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I found my ST70 in a pile of old, used, lab equipment in the hallway of
the university where I worked. It was waiting to be taken to the dump. I gave
it a new home for the price of picking it up.
Jim |
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