Tantalum Capacitors

B

bitrex

Guest
So I'm working on repairing a Korg MS2000B synthesizer for a friend with
a dead power supply. Here's the service manual:

http://www.loscha.com/scans/Korg_MS2000_Service_Manual.pdf

The first thing I notice when looking inside is that the small SMT 100uF
10V tantalum capacitor C109 has completely vacated - it appears to be
gone, blown right off the board. There are some little fragments
rattling around in the case.

I have little experience with tantalum capacitors. Any suggestions for
a more reliable replacement?
 
"bitrex" <bitrex@de.lete.earthlink.net> wrote in message
news:5601ad59$0$5917$4c5ecfc7@frugalusenet.com...
So I'm working on repairing a Korg MS2000B synthesizer for a friend with a
dead power supply. Here's the service manual:

http://www.loscha.com/scans/Korg_MS2000_Service_Manual.pdf

The first thing I notice when looking inside is that the small SMT 100uF
10V tantalum capacitor C109 has completely vacated - it appears to be
gone, blown right off the board. There are some little fragments rattling
around in the case.

I have little experience with tantalum capacitors. Any suggestions for a
more reliable replacement?
Click to expand...

Use 2.5 times the applied voltage or more.

Or use an aluminum electrolytic 2 - 3 times capacitance.
 
On Tue, 22 Sep 2015 15:34:51 -0400, bitrex
<bitrex@de.lete.earthlink.net> wrote:

So I'm working on repairing a Korg MS2000B synthesizer for a friend with
a dead power supply. Here's the service manual:

http://www.loscha.com/scans/Korg_MS2000_Service_Manual.pdf

The first thing I notice when looking inside is that the small SMT 100uF
10V tantalum capacitor C109 has completely vacated - it appears to be
gone, blown right off the board. There are some little fragments
rattling around in the case.

I have little experience with tantalum capacitors. Any suggestions for
a more reliable replacement?
Click to expand...

I don't think there's a reliability issue here. C109 (located on the
Power / MIDI board schematic, is the initial output filter capacitor
in a 3.3V switching power supply. There are other 100 uf caps
surrounding it, but it seems to be the only tantalum cap, which
suggests that the designer needed some specific characteristic of the
cap to make things work. Methinks a change of capacitor type might
not be such a great idea.

What would make the cap explode? My guess(tm) is that someone plugged
in a wrong voltage power supply, which blew up FET (F1) which then
applied overvoltage to the tantalum. It much have been quite a large
jolt as tantalums using produce a low resistance "short" which then
gets hot and starts smoking toxic fumes. I would look around for
other parts in the power supply section that may be been destroyed,
such as the other caps along the 3.3V rail.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On 9/22/2015 3:56 PM, Jeff Liebermann wrote:
On Tue, 22 Sep 2015 15:34:51 -0400, bitrex
bitrex@de.lete.earthlink.net> wrote:

So I'm working on repairing a Korg MS2000B synthesizer for a friend with
a dead power supply. Here's the service manual:

http://www.loscha.com/scans/Korg_MS2000_Service_Manual.pdf

The first thing I notice when looking inside is that the small SMT 100uF
10V tantalum capacitor C109 has completely vacated - it appears to be
gone, blown right off the board. There are some little fragments
rattling around in the case.

I have little experience with tantalum capacitors. Any suggestions for
a more reliable replacement?

I don't think there's a reliability issue here. C109 (located on the
Power / MIDI board schematic, is the initial output filter capacitor
in a 3.3V switching power supply. There are other 100 uf caps
surrounding it, but it seems to be the only tantalum cap, which
suggests that the designer needed some specific characteristic of the
cap to make things work. Methinks a change of capacitor type might
not be such a great idea.

What would make the cap explode? My guess(tm) is that someone plugged
in a wrong voltage power supply, which blew up FET (F1) which then
applied overvoltage to the tantalum. It much have been quite a large
jolt as tantalums using produce a low resistance "short" which then
gets hot and starts smoking toxic fumes. I would look around for
other parts in the power supply section that may be been destroyed,
such as the other caps along the 3.3V rail.
Click to expand...

I notice now that there seems to be some very light heat discoloration
around the common mode choke L10-L11-L12.

I don't see anything immediately wrong with F1 and it passes the "smell
test" so I dunno.
 
On Tue, 22 Sep 2015 12:56:56 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Tue, 22 Sep 2015 15:34:51 -0400, bitrex
bitrex@de.lete.earthlink.net> wrote:

So I'm working on repairing a Korg MS2000B synthesizer for a friend with
a dead power supply. Here's the service manual:

http://www.loscha.com/scans/Korg_MS2000_Service_Manual.pdf

The first thing I notice when looking inside is that the small SMT 100uF
10V tantalum capacitor C109 has completely vacated - it appears to be
gone, blown right off the board. There are some little fragments
rattling around in the case.

I have little experience with tantalum capacitors. Any suggestions for
a more reliable replacement?

I don't think there's a reliability issue here. C109 (located on the
Power / MIDI board schematic, is the initial output filter capacitor
in a 3.3V switching power supply. There are other 100 uf caps
surrounding it, but it seems to be the only tantalum cap, which
suggests that the designer needed some specific characteristic of the
cap to make things work. Methinks a change of capacitor type might
not be such a great idea.

What would make the cap explode? My guess(tm) is that someone plugged
in a wrong voltage power supply, which blew up FET (F1) which then
applied overvoltage to the tantalum. It much have been quite a large
jolt as tantalums using produce a low resistance "short" which then
gets hot and starts smoking toxic fumes. I would look around for
other parts in the power supply section that may be been destroyed,
such as the other caps along the 3.3V rail.
Click to expand...

Dry-slug tantalums across power rails are bad news. High dV/dT
literally ignites them; MnO2 is the oxidizer and tantalum is the fuel.

Derate them 3:1 on voltage, or use something else. Polymer aluminums
are good, and some come in a tantalum-like surface mount package.
 
On 22/09/2015 21:40, John Larkin wrote:
On Tue, 22 Sep 2015 12:56:56 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:

On Tue, 22 Sep 2015 15:34:51 -0400, bitrex
bitrex@de.lete.earthlink.net> wrote:

So I'm working on repairing a Korg MS2000B synthesizer for a friend with
a dead power supply. Here's the service manual:

http://www.loscha.com/scans/Korg_MS2000_Service_Manual.pdf

The first thing I notice when looking inside is that the small SMT 100uF
10V tantalum capacitor C109 has completely vacated - it appears to be
gone, blown right off the board. There are some little fragments
rattling around in the case.

I have little experience with tantalum capacitors. Any suggestions for
a more reliable replacement?

I don't think there's a reliability issue here. C109 (located on the
Power / MIDI board schematic, is the initial output filter capacitor
in a 3.3V switching power supply. There are other 100 uf caps
surrounding it, but it seems to be the only tantalum cap, which
suggests that the designer needed some specific characteristic of the
cap to make things work. Methinks a change of capacitor type might
not be such a great idea.

What would make the cap explode? My guess(tm) is that someone plugged
in a wrong voltage power supply, which blew up FET (F1) which then
applied overvoltage to the tantalum. It much have been quite a large
jolt as tantalums using produce a low resistance "short" which then
gets hot and starts smoking toxic fumes. I would look around for
other parts in the power supply section that may be been destroyed,
such as the other caps along the 3.3V rail.

Dry-slug tantalums across power rails are bad news. High dV/dT
literally ignites them; MnO2 is the oxidizer and tantalum is the fuel.

Derate them 3:1 on voltage, or use something else. Polymer aluminums
are good, and some come in a tantalum-like surface mount package.
Click to expand...

+1

Cheers
--
Syd
 
On 9/22/2015 4:40 PM, John Larkin wrote:
On Tue, 22 Sep 2015 12:56:56 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:

On Tue, 22 Sep 2015 15:34:51 -0400, bitrex
bitrex@de.lete.earthlink.net> wrote:

So I'm working on repairing a Korg MS2000B synthesizer for a friend with
a dead power supply. Here's the service manual:

http://www.loscha.com/scans/Korg_MS2000_Service_Manual.pdf

The first thing I notice when looking inside is that the small SMT 100uF
10V tantalum capacitor C109 has completely vacated - it appears to be
gone, blown right off the board. There are some little fragments
rattling around in the case.

I have little experience with tantalum capacitors. Any suggestions for
a more reliable replacement?

I don't think there's a reliability issue here. C109 (located on the
Power / MIDI board schematic, is the initial output filter capacitor
in a 3.3V switching power supply. There are other 100 uf caps
surrounding it, but it seems to be the only tantalum cap, which
suggests that the designer needed some specific characteristic of the
cap to make things work. Methinks a change of capacitor type might
not be such a great idea.

What would make the cap explode? My guess(tm) is that someone plugged
in a wrong voltage power supply, which blew up FET (F1) which then
applied overvoltage to the tantalum. It much have been quite a large
jolt as tantalums using produce a low resistance "short" which then
gets hot and starts smoking toxic fumes. I would look around for
other parts in the power supply section that may be been destroyed,
such as the other caps along the 3.3V rail.

Dry-slug tantalums across power rails are bad news. High dV/dT
literally ignites them; MnO2 is the oxidizer and tantalum is the fuel.

Derate them 3:1 on voltage, or use something else. Polymer aluminums
are good, and some come in a tantalum-like surface mount package.
Click to expand...

Is there anything I can use temporarily in its place, that I might have
in stock, to try and get that switcher up and running while I wait for
the appropriate part?
 
In sci.electronics.repair John Larkin <jjlarkin@highlandtechnology.com> wrote:
On Tue, 22 Sep 2015 15:34:51 -0400, bitrex
bitrex@de.lete.earthlink.net> wrote:

http://www.loscha.com/scans/Korg_MS2000_Service_Manual.pdf

What's with the 21 resistors between AGND and DGND? That's crazy.
Click to expand...

They're all marked "NU", which seems to mean Not Used. Other parts of
that sheet have "NU" resistors in similar nonsensical places, like
across the fuse or across the power switch. I suspect there are places
for all of these resistors on the board, but they don't populate them at
the factory except for test.

Matt Roberds
 
On Tue, 22 Sep 2015 20:22:49 -0400, bitrex
<bitrex@de.lete.earthlink.net> wrote:

On 9/22/2015 4:40 PM, John Larkin wrote:
On Tue, 22 Sep 2015 12:56:56 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:

On Tue, 22 Sep 2015 15:34:51 -0400, bitrex
bitrex@de.lete.earthlink.net> wrote:

So I'm working on repairing a Korg MS2000B synthesizer for a friend with
a dead power supply. Here's the service manual:

http://www.loscha.com/scans/Korg_MS2000_Service_Manual.pdf
Click to expand...

What a horrible schematic! A mosfet is "F1" and a fuse is "FU1" !
Connector names are all over the place. And worse.

Replace C109 with most any 100 uF cap.

What's with the 21 resistors between AGND and DGND? That's crazy.
 
On Tue, 22 Sep 2015 13:40:36 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

Dry-slug tantalums across power rails are bad news. High dV/dT
literally ignites them; MnO2 is the oxidizer and tantalum is the fuel.
Click to expand...

That's what I've read everywhere. Yet, I spent 10 years shipping
marine radios that were literally crammed with dipped and molded
tantalum caps on power supply rails with never a problem. The only
ones I've ever seen go up in smoke were reverse polarized (which
produced an impressive red glowing piece of slag and plenty of white
smog). Mostly, these caps were 25V caps on the 12V (nominal) power
supply lines and 16V caps on the 8 and 10V regulated lines. There
were also a bunch used in audio circuits.

However, we never used tantalums on the output of a switcher, where I
would expect problems. I guess using a tantalum in this 3.3V switcher
would qualify. However, at the time (1970's) the literature declared
that high voltage spikes were the culprit, not voltage slew rate.
Since these often appear together, I can see where there might be some
confusion.

Derate them 3:1 on voltage, or use something else. Polymer aluminums
are good, and some come in a tantalum-like surface mount package.
Click to expand...

The original cap is a 100uF 10v tantalum which is already 3:1 derated
in a 3.3 VDC power supply. However, that doesn't included voltage
spikes from the nearby inductor.

Judging by the age of the Korg, I would guess(tm) axial leads not SMT.
100uf 10-16V From Digikey:
<http://www.digikey.com/product-search/en?pv13=67&pv63=19&pv63=11&pv63=449&pv63=489&pv69=80&FV=fff40002%2Cfff80532&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25>
For fast delivery, there's probably something on eBay:
<http://www.ebay.com/sch/i.html?_nkw=polymer+capacitor+100uf>


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On 9/22/2015 8:55 PM, Jeff Liebermann wrote:
On Tue, 22 Sep 2015 13:40:36 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

Dry-slug tantalums across power rails are bad news. High dV/dT
literally ignites them; MnO2 is the oxidizer and tantalum is the fuel.

That's what I've read everywhere. Yet, I spent 10 years shipping
marine radios that were literally crammed with dipped and molded
tantalum caps on power supply rails with never a problem. The only
ones I've ever seen go up in smoke were reverse polarized (which
produced an impressive red glowing piece of slag and plenty of white
smog). Mostly, these caps were 25V caps on the 12V (nominal) power
supply lines and 16V caps on the 8 and 10V regulated lines. There
were also a bunch used in audio circuits.

However, we never used tantalums on the output of a switcher, where I
would expect problems. I guess using a tantalum in this 3.3V switcher
would qualify. However, at the time (1970's) the literature declared
that high voltage spikes were the culprit, not voltage slew rate.
Since these often appear together, I can see where there might be some
confusion.

Derate them 3:1 on voltage, or use something else. Polymer aluminums
are good, and some come in a tantalum-like surface mount package.

The original cap is a 100uF 10v tantalum which is already 3:1 derated
in a 3.3 VDC power supply. However, that doesn't included voltage
spikes from the nearby inductor.

Judging by the age of the Korg, I would guess(tm) axial leads not SMT.
100uf 10-16V From Digikey:
http://www.digikey.com/product-search/en?pv13=67&pv63=19&pv63=11&pv63=449&pv63=489&pv69=80&FV=fff40002%2Cfff80532&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25
For fast delivery, there's probably something on eBay:
http://www.ebay.com/sch/i.html?_nkw=polymer+capacitor+100uf
Click to expand...

Nope, the power supply is almost all SMT, including the tantalum. The
only through hole parts is the switcher inductor and the other large
capacitors, which are a mix of organic polymer and regular electrolytic.
 
On 9/22/2015 8:55 PM, Jeff Liebermann wrote:
On Tue, 22 Sep 2015 13:40:36 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

Dry-slug tantalums across power rails are bad news. High dV/dT
literally ignites them; MnO2 is the oxidizer and tantalum is the fuel.

That's what I've read everywhere. Yet, I spent 10 years shipping
marine radios that were literally crammed with dipped and molded
tantalum caps on power supply rails with never a problem. The only
ones I've ever seen go up in smoke were reverse polarized (which
produced an impressive red glowing piece of slag and plenty of white
smog). Mostly, these caps were 25V caps on the 12V (nominal) power
supply lines and 16V caps on the 8 and 10V regulated lines. There
were also a bunch used in audio circuits.

However, we never used tantalums on the output of a switcher, where I
would expect problems. I guess using a tantalum in this 3.3V switcher
would qualify. However, at the time (1970's) the literature declared
that high voltage spikes were the culprit, not voltage slew rate.
Since these often appear together, I can see where there might be some
confusion.

Derate them 3:1 on voltage, or use something else. Polymer aluminums
are good, and some come in a tantalum-like surface mount package.

The original cap is a 100uF 10v tantalum which is already 3:1 derated
in a 3.3 VDC power supply. However, that doesn't included voltage
spikes from the nearby inductor.

Judging by the age of the Korg, I would guess(tm) axial leads not SMT.
100uf 10-16V From Digikey:
http://www.digikey.com/product-search/en?pv13=67&pv63=19&pv63=11&pv63=449&pv63=489&pv69=80&FV=fff40002%2Cfff80532&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25
For fast delivery, there's probably something on eBay:
http://www.ebay.com/sch/i.html?_nkw=polymer+capacitor+100uf
Click to expand...

This thing cost an arm and a leg when it was new 15 years ago. Inside
the very large case there actually isn't very much - there's a board
which holds all the front panel controls, and everything else including
the power supply and output jacks are on a single mainboard measuring
maybe 8"x10".
 
On Tue, 22 Sep 2015 17:55:51 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Tue, 22 Sep 2015 13:40:36 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

Dry-slug tantalums across power rails are bad news. High dV/dT
literally ignites them; MnO2 is the oxidizer and tantalum is the fuel.

That's what I've read everywhere. Yet, I spent 10 years shipping
marine radios that were literally crammed with dipped and molded
tantalum caps on power supply rails with never a problem. The only
ones I've ever seen go up in smoke were reverse polarized (which
produced an impressive red glowing piece of slag and plenty of white
smog). Mostly, these caps were 25V caps on the 12V (nominal) power
supply lines and 16V caps on the 8 and 10V regulated lines. There
were also a bunch used in audio circuits.
Click to expand...

The tantalum thing is very erratic. Some batches blow up, some are
fine.


However, we never used tantalums on the output of a switcher, where I
would expect problems. I guess using a tantalum in this 3.3V switcher
would qualify. However, at the time (1970's) the literature declared
that high voltage spikes were the culprit, not voltage slew rate.
Since these often appear together, I can see where there might be some
confusion.
Click to expand...

I know for sure that tantalums sometimes blow up at below their rated
voltages, with no overshoot spikes. It's dV/dT, namely peak current,
that can ignite tiny particles of tantalum, which then burn in the
solid MnO2 electrolyte.


Derate them 3:1 on voltage, or use something else. Polymer aluminums
are good, and some come in a tantalum-like surface mount package.

The original cap is a 100uF 10v tantalum which is already 3:1 derated
in a 3.3 VDC power supply. However, that doesn't included voltage
spikes from the nearby inductor.
Click to expand...

Could be. Or maybe there was a lot of dV/dT. Or maybe some other
failure mechanism.

Tantalums are just right for some things, but have to be used
carefully.

https://dl.dropboxusercontent.com/u/53724080/Parts/Caps/Bang.jpg

https://dl.dropboxusercontent.com/u/53724080/Parts/Caps/Fried_Tant_1.JPG
 
On Tue, 22 Sep 2015 21:23:47 -0400, bitrex
<bitrex@de.lete.earthlink.net> wrote:

Judging by the age of the Korg, I would guess(tm) axial leads not SMT.
100uf 10-16V From Digikey:
http://www.digikey.com/product-search/en?pv13=67&pv63=19&pv63=11&pv63=449&pv63=489&pv69=80&FV=fff40002%2Cfff80532&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25
For fast delivery, there's probably something on eBay:
http://www.ebay.com/sch/i.html?_nkw=polymer+capacitor+100uf

Nope, the power supply is almost all SMT, including the tantalum. The
only through hole parts is the switcher inductor and the other large
capacitors, which are a mix of organic polymer and regular electrolytic.
Click to expand...

Bad guess(tm). Sorry. I couldn't tell from the "manual" because none
of the caps are listed in the parts list.

This should work for SMT on Digikey:
<http://www.digikey.com/product-search/en?pv13=67&pv63=19&pv63=11&pv63=449&pv63=489&pv69=3&FV=fff40002%2Cfff80532&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25>
The eBay link includes both through-hole and SMT.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
On 23/09/2015 5:34 AM, bitrex wrote:
So I'm working on repairing a Korg MS2000B synthesizer for a friend with
a dead power supply. Here's the service manual:

http://www.loscha.com/scans/Korg_MS2000_Service_Manual.pdf

The first thing I notice when looking inside is that the small SMT 100uF
10V tantalum capacitor C109 has completely vacated - it appears to be
gone, blown right off the board. There are some little fragments
rattling around in the case.

I have little experience with tantalum capacitors. Any suggestions for
a more reliable replacement?
Click to expand...

**Tants are not unreliable. In fact, IME, they're more reliable than
aluminium electros (not a scientific study though - just seat of the
pants). They do not tolerate reverse Voltages particularly well though.

Use another tantalum. Solid are best, but hard to find.

--
Trevor Wilson
www.rageaudio.com.au

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
 
On Tue, 22 Sep 2015 17:55:51 -0700, Jeff Liebermann wrote:

On Tue, 22 Sep 2015 13:40:36 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

Dry-slug tantalums across power rails are bad news. High dV/dT literally
ignites them; MnO2 is the oxidizer and tantalum is the fuel.

That's what I've read everywhere. Yet, I spent 10 years shipping marine
radios that were literally crammed with dipped and molded tantalum caps
on power supply rails with never a problem. The only ones I've ever
seen go up in smoke were reverse polarized (which produced an impressive
red glowing piece of slag and plenty of white smog). Mostly, these caps
were 25V caps on the 12V (nominal) power supply lines and 16V caps on
the 8 and 10V regulated lines. There were also a bunch used in audio
circuits.

However, we never used tantalums on the output of a switcher, where I
would expect problems. I guess using a tantalum in this 3.3V switcher
would qualify. However, at the time (1970's) the literature declared
that high voltage spikes were the culprit, not voltage slew rate.
Since these often appear together, I can see where there might be some
confusion.
Click to expand...

Tantalums have such a low HF resistance that it is sometimes recommended
to put a current limiting resistor in series if there is a serious ripple
voltage around. I've witnessed a lot of IGBT's being blown up because
those resistors were failing. The voltage feeding the tantalums had such
a large HF ripple due to the switching of the IGBT's that it blew the
tantalums out of the control board, after which the IGBT's also went to
pieces.

joe


Derate them 3:1 on voltage, or use something else. Polymer aluminums are
good, and some come in a tantalum-like surface mount package.

The original cap is a 100uF 10v tantalum which is already 3:1 derated in
a 3.3 VDC power supply. However, that doesn't included voltage spikes
from the nearby inductor.

Judging by the age of the Korg, I would guess(tm) axial leads not SMT.
100uf 10-16V From Digikey:
http://www.digikey.com/product-search/en?
Click to expand...
pv13=67&pv63=19&pv63=11&pv63=449&pv63=489&pv69=80&FV=fff40002%
2Cfff80532&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25>
For fast delivery, there's probably something on eBay:
http://www.ebay.com/sch/i.html?_nkw=polymer+capacitor+100uf
Click to expand...
 
On Tue, 22 Sep 2015 19:02:33 -0700, John Larkin wrote:

On Tue, 22 Sep 2015 17:55:51 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:

On Tue, 22 Sep 2015 13:40:36 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

Dry-slug tantalums across power rails are bad news. High dV/dT
literally ignites them; MnO2 is the oxidizer and tantalum is the fuel.

That's what I've read everywhere. Yet, I spent 10 years shipping marine
radios that were literally crammed with dipped and molded tantalum caps
on power supply rails with never a problem. The only ones I've ever
seen go up in smoke were reverse polarized (which produced an impressive
red glowing piece of slag and plenty of white smog). Mostly, these caps
were 25V caps on the 12V (nominal) power supply lines and 16V caps on
the 8 and 10V regulated lines. There were also a bunch used in audio
circuits.

The tantalum thing is very erratic. Some batches blow up, some are fine.



However, we never used tantalums on the output of a switcher, where I
would expect problems. I guess using a tantalum in this 3.3V switcher
would qualify. However, at the time (1970's) the literature declared
that high voltage spikes were the culprit, not voltage slew rate. Since
these often appear together, I can see where there might be some
confusion.

I know for sure that tantalums sometimes blow up at below their rated
voltages, with no overshoot spikes. It's dV/dT, namely peak current,
that can ignite tiny particles of tantalum, which then burn in the solid
MnO2 electrolyte.
Click to expand...

That's why in those cases a series resistor might be recommended in order
to limit the current spikes.

joe

Derate them 3:1 on voltage, or use something else. Polymer aluminums
are good, and some come in a tantalum-like surface mount package.

The original cap is a 100uF 10v tantalum which is already 3:1 derated in
a 3.3 VDC power supply. However, that doesn't included voltage spikes
from the nearby inductor.

Could be. Or maybe there was a lot of dV/dT. Or maybe some other failure
mechanism.

Tantalums are just right for some things, but have to be used carefully.

https://dl.dropboxusercontent.com/u/53724080/Parts/Caps/Bang.jpg

https://dl.dropboxusercontent.com/u/53724080/Parts/Caps/Fried_Tant_1.JPG
Click to expand...
 
On 9/23/2015 12:20 AM, joe hey wrote:
On Tue, 22 Sep 2015 19:02:33 -0700, John Larkin wrote:

On Tue, 22 Sep 2015 17:55:51 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:

On Tue, 22 Sep 2015 13:40:36 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

Dry-slug tantalums across power rails are bad news. High dV/dT
literally ignites them; MnO2 is the oxidizer and tantalum is the fuel.

That's what I've read everywhere. Yet, I spent 10 years shipping marine
radios that were literally crammed with dipped and molded tantalum caps
on power supply rails with never a problem. The only ones I've ever
seen go up in smoke were reverse polarized (which produced an impressive
red glowing piece of slag and plenty of white smog). Mostly, these caps
were 25V caps on the 12V (nominal) power supply lines and 16V caps on
the 8 and 10V regulated lines. There were also a bunch used in audio
circuits.

The tantalum thing is very erratic. Some batches blow up, some are fine.



However, we never used tantalums on the output of a switcher, where I
would expect problems. I guess using a tantalum in this 3.3V switcher
would qualify. However, at the time (1970's) the literature declared
that high voltage spikes were the culprit, not voltage slew rate. Since
these often appear together, I can see where there might be some
confusion.

I know for sure that tantalums sometimes blow up at below their rated
voltages, with no overshoot spikes. It's dV/dT, namely peak current,
that can ignite tiny particles of tantalum, which then burn in the solid
MnO2 electrolyte.


That's why in those cases a series resistor might be recommended in order
to limit the current spikes.
Click to expand...

Add series resistance to a tantalum cap and you have just created an
electrolytic replacement.

--

Rick
 
On Wed, 23 Sep 2015 00:40:00 -0400, rickman wrote:

On 9/23/2015 12:20 AM, joe hey wrote:
On Tue, 22 Sep 2015 19:02:33 -0700, John Larkin wrote:

On Tue, 22 Sep 2015 17:55:51 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:

On Tue, 22 Sep 2015 13:40:36 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

Dry-slug tantalums across power rails are bad news. High dV/dT
literally ignites them; MnO2 is the oxidizer and tantalum is the
fuel.

That's what I've read everywhere. Yet, I spent 10 years shipping
marine radios that were literally crammed with dipped and molded
tantalum caps on power supply rails with never a problem. The only
ones I've ever seen go up in smoke were reverse polarized (which
produced an impressive red glowing piece of slag and plenty of white
smog). Mostly, these caps were 25V caps on the 12V (nominal) power
supply lines and 16V caps on the 8 and 10V regulated lines. There
were also a bunch used in audio circuits.

The tantalum thing is very erratic. Some batches blow up, some are
fine.



However, we never used tantalums on the output of a switcher, where I
would expect problems. I guess using a tantalum in this 3.3V
switcher would qualify. However, at the time (1970's) the literature
declared that high voltage spikes were the culprit, not voltage slew
rate. Since these often appear together, I can see where there might
be some confusion.

I know for sure that tantalums sometimes blow up at below their rated
voltages, with no overshoot spikes. It's dV/dT, namely peak current,
that can ignite tiny particles of tantalum, which then burn in the
solid MnO2 electrolyte.


That's why in those cases a series resistor might be recommended in
order to limit the current spikes.

Add series resistance to a tantalum cap and you have just created an
electrolytic replacement.
Click to expand...

Sorry, I forgot to mention to put the resistance in between the power
line and the tantalum.

joe
 
In sci.electronics.repair Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 09/22/2015 06:18 PM, Syd Rumpo wrote:
On 22/09/2015 21:40, John Larkin wrote:
On Tue, 22 Sep 2015 12:56:56 -0700, Jeff Liebermann <jeffl@cruzio.com
wrote:

On Tue, 22 Sep 2015 15:34:51 -0400, bitrex
bitrex@de.lete.earthlink.net> wrote:

So I'm working on repairing a Korg MS2000B synthesizer for a friend
with
a dead power supply. Here's the service manual:

http://www.loscha.com/scans/Korg_MS2000_Service_Manual.pdf

The first thing I notice when looking inside is that the small SMT
100uF
10V tantalum capacitor C109 has completely vacated - it appears to be
gone, blown right off the board. There are some little fragments
rattling around in the case.

I have little experience with tantalum capacitors. Any suggestions for
a more reliable replacement?

I don't think there's a reliability issue here. C109 (located on the
Power / MIDI board schematic, is the initial output filter capacitor
in a 3.3V switching power supply. There are other 100 uf caps
surrounding it, but it seems to be the only tantalum cap, which
suggests that the designer needed some specific characteristic of the
cap to make things work. Methinks a change of capacitor type might
not be such a great idea.

What would make the cap explode? My guess(tm) is that someone plugged
in a wrong voltage power supply, which blew up FET (F1) which then
applied overvoltage to the tantalum. It much have been quite a large
jolt as tantalums using produce a low resistance "short" which then
gets hot and starts smoking toxic fumes. I would look around for
other parts in the power supply section that may be been destroyed,
such as the other caps along the 3.3V rail.

Dry-slug tantalums across power rails are bad news. High dV/dT
literally ignites them; MnO2 is the oxidizer and tantalum is the fuel.

Derate them 3:1 on voltage, or use something else. Polymer aluminums
are good, and some come in a tantalum-like surface mount package.

+1

Cheers

Al polys can make voltage regulators oscillate. Tantalums have a nice
middle-of-the-road ESR that makes 7800s happy.

The ignition problem is quite real--see
http://electrooptical.net/www/sed/TantalumCapReforming_25272-what_a_cap_astrophe.pdf
Click to expand...

Can somebody decode "postprocessing fixture" back into English? I have
idea what the author is talking about or what the "fix" really was.
 
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