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Capacitor

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November 15, 2004 11:23:49 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

Hello,

perhaps this is dumb, but I do not know an answer.

I got 2 machines at work which work like a charm. No hangups, no bluescreen.
Perfect.

Now as I opened them for cleaning I noticed 2 capacitors with brown crusting
on the top. Seems as they had those for a little while. Nowhere else was the
crusting and it has dried.

Now my question is: The machines work, without a flaw, beleve it or not. Do
I have to change the mobo´s (boards) or can I stick with the present ones?
Like never change a running system?

Thanks for any advice-

More about : capacitor

Anonymous
a b V Motherboard
November 15, 2004 11:23:50 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Frank" <schmidt@bth.de> wrote in message
news:419902ad$0$154$9b622d9e@news.freenet.de...
| Hello,
|
| perhaps this is dumb, but I do not know an answer.
|
| I got 2 machines at work which work like a charm. No hangups, no
bluescreen.
| Perfect.
|
| Now as I opened them for cleaning I noticed 2 capacitors with brown
crusting
| on the top. Seems as they had those for a little while. Nowhere else
was the
| crusting and it has dried.
|
| Now my question is: The machines work, without a flaw, beleve it or
not. Do
| I have to change the mobo´s (boards) or can I stick with the present
ones?
| Like never change a running system?
|
| Thanks for any advice-
|
|

Typically, an electrolytic capacitor (a metal cylindrical can with a
rubber plug in one end, and 2 leads protruding out of the rubber plug)
will leak at the end where the rubber plug or seal is inserted.
Additionally, when they go bad, oftentimes an electrolytic capacitor
will "bulge" on top due to the internal pressure generated when the
cap got to hot and the electrolyte therein vaporized thus causing
extreme pressure to buildup internally. Perhaps if you can post a
picture on the net, informed users could comment. It is rather
unusual for a cap to allow fluid to leak out the "metal" side of the
can, tho I suppose anything is possible.
--
Best regards,
Kyle
Anonymous
a b V Motherboard
November 15, 2004 11:32:46 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <419902ad$0$154$9b622d9e@news.freenet.de>, schmidt@bth.de
says...
> Hello,
>
> perhaps this is dumb, but I do not know an answer.
>
> I got 2 machines at work which work like a charm. No hangups, no bluescreen.
> Perfect.
>
> Now as I opened them for cleaning I noticed 2 capacitors with brown crusting
> on the top. Seems as they had those for a little while. Nowhere else was the
> crusting and it has dried.
>
> Now my question is: The machines work, without a flaw, beleve it or not. Do
> I have to change the mobo=3Fs (boards) or can I stick with the present ones?
> Like never change a running system?

Caps, the ones you're talking about, filter ripples out of the power
signal and provide a stable (flat) voltage for the circuitry to use.

A cap that has bulged or busted, even around the "X" or "/" pattern on
the top is indeed defective. There are two things that commonly happen
to the circuit when this happens:

1) The filtering of the ripple is nullified and causes the voltage to
ripple which may or may not have an immediate impact on the system. It
is possible that the defective cap, if not shorted, will have no impact
on the system that you can see.

2) The cap, can short - meaning that it will cross the + and ground
lines and can burn the traces on the motherboard, can cause a section of
the board to stop working, and cause a small fire.

In any even the solution that first bubbles out of the cap is corrosive
and can, over time, even when it looks dry, can eat through traces on
the board - even when it looks dry it can absorb moisture out of the
air.

Replace the CAP as soon as possible or at least remove it.

--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
Related resources
November 16, 2004 12:11:46 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

> Typically, an electrolytic capacitor (a metal cylindrical can with a
> rubber plug in one end, and 2 leads protruding out of the rubber plug)
> will leak at the end where the rubber plug or seal is inserted.
> Additionally, when they go bad, oftentimes an electrolytic capacitor
> will "bulge" on top due to the internal pressure generated when the
> cap got to hot and the electrolyte therein vaporized thus causing
> extreme pressure to buildup internally. Perhaps if you can post a
> picture on the net, informed users could comment. It is rather
> unusual for a cap to allow fluid to leak out the "metal" side of the
> can, tho I suppose anything is possible.
> --
> Best regards,
> Kyle

First thanks for the reply, but is is exactly as you said it normally cannot
be.

On the top of the thingie, there are two curves in the metal cover where the
capacitor should break up if the pressure is too big. It seems that it broke
up, but only that far that a liitle amount of electrolyte came out like two
or three needle tops. This dried on the top, I think sealing it again. It
stands perfectly flat on the mobo, no rubber out or else, just a little
brown dried liquid on the top, really not more than 2 or 3 needle tops, or
heads, sorry I´m German, do not know the exact word for it.

Frank
November 16, 2004 12:45:13 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

> air.
>
> Replace the CAP as soon as possible or at least remove it.
>
> --

What do you mean? Remove the Cap of the capacitor or the whole capacitor? If
I remove the cap of the capacitor it will be open. I?m not good at
soldering, so I won?t be able to solder a new one onto it.
Anonymous
a b V Motherboard
November 16, 2004 12:45:14 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <419915be$0$179$9b622d9e@news.freenet.de>, schmidt@bth.de
says...
> > air.
> >
> > Replace the CAP as soon as possible or at least remove it.
> >
> > --
>
> What do you mean? Remove the Cap of the capacitor or the whole capacitor? If
> I remove the cap of the capacitor it will be open. I?m not good at
> soldering, so I won?t be able to solder a new one onto it.

There is no "CAP" on a capacitor - the term CAP means Capacitor in the
industry. What I was suggesting was, if you are not going to have it
replaced, then you would be better served my completely removing it,
cleaning the area with 99% alcohol. ALL POWER MUST BE REMOVED BEFORE
ATTEMPTING A DEVICE REMOVAL, not just turned off, actually remove the
power cord from the power supply, remove any device connections (modem,
monitor, scanner, USB devices....).

If you can't solder, if you can get near it, you could just clip the
leads (but I'm betting that you can't even see the leads).

You may get years of trouble free operation, or it may die in seconds,
it may short out and take the board with it, or the corrosive
electrolyte may eat through something.... In any case, I would remove it
at the very least and clean it.



--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
November 16, 2004 12:50:24 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

>
> 1) The filtering of the ripple is nullified and causes the voltage to
> ripple which may or may not have an immediate impact on the system. It
> is possible that the defective cap, if not shorted, will have no impact
> on the system that you can see.
>

Thinking again, the defective caps are near the AGP slot and the LCD
connected to the Geforce MX shows colour differencies in a solid colour
screnn. What I try to say is that the screen is divided into three section
that look like ribbons in slight different colour.

Could that behaviour be related to the caps?

I did not think of these effect because I thought it mitght be related to 8
hours use a day for 3 years now.
Is it obious these effects are leated? I must say that the LCD does not
chance if I chande brightness and contrast in the OSD of the LCD, so I think
it is a LCD problem and not related to the Mobo.


Frank
Anonymous
a b V Motherboard
November 16, 2004 2:44:31 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

Am Mon, 15 Nov 2004 21:11:46 +0100 schrieb Frank:

[Kondensatorenprobleme]

> heads, sorry I´m German, do not know the exact word for it.

Wenn du sowieso aus Deutschland kommst, antworte ich einfach auch mal auf
deutsch ;)  Über kurz oder lang werden sich die geplatzten Kondensatoren
bemerkbar machen. Bei mir ist das System dann immer sporadisch eingefroren
(nach einem Reset lief es direkt wieder). Davon, die Kondensatoren selbst
auszutauschen, würde ich dir dringend abraten. Du machst mit an Sicherheit
grenzender Wahrscheinlichkeit mehr kaputt, als du reparierst (es sei denn,
du bist zufällig vom Fach). Solltest du noch Garantie haben: nichts wie hin
zum Händler und reparieren/tauschen lassen. Sollte normalerweise problemlos
über die Bühne gehen, da die Probleme mit den defekten Kondensatoren
mittlerweile wohl bei jedem Hersteller bekannt sind. Wenn nicht, arbeite
solange es geht mit dem Board weiter und tausch es gegen ein Neues aus,
sobald Fehler auftreten.

HTH

Gruß
Carsten
November 16, 2004 3:17:48 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Leythos" <void@nowhere.org> wrote in message
news:MPG.1c02dd7c4ad1dc9c989a57@news-server.columbus.rr.com...
>
> Replace the CAP as soon as possible or at least remove it.

Removing a cap from a switching power supply, where it is likely to belong,
might disable the board completely. I actually found a similar problem on my
old Aopen mobo (in my case the caps are definitely belong to the main CPU
switching power supply), so I went and bought a new ASUS mobo :)  But I am
going to replace the caps on the old board and then build a second computer.

/MM
Anonymous
a b V Motherboard
November 16, 2004 8:29:43 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <dqWdndAEi68TEATcRVn-1Q@rogers.com>, mbmsv@yahoo.com says...
> "Leythos" <void@nowhere.org> wrote in message
> news:MPG.1c02dd7c4ad1dc9c989a57@news-server.columbus.rr.com...
> >
> > Replace the CAP as soon as possible or at least remove it.
>
> Removing a cap from a switching power supply, where it is likely to belong,
> might disable the board completely. I actually found a similar problem on my
> old Aopen mobo (in my case the caps are definitely belong to the main CPU
> switching power supply), so I went and bought a new ASUS mobo :)  But I am
> going to replace the caps on the old board and then build a second computer.

The onboard PSU is normally not a switching unit, the Switching PSU's
are the large metal units that you connect AC to. Most of the
"regulators" on the motherboard have no PSU to them, they are just
voltage regulators. A regulator, using the existing DC signal from the
PSU, uses the CAP's to clean the ripple out of the "switched" DC supply
from the PSU.

Removing a CAP, from the PSU would indeed cause problems, as they use
the caps to provide ripple rejection to the DC output.

The caps on a motherboard, in almost every instance, are to spot signal
filtering or for ripple rejection at the point.

--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
November 16, 2004 8:29:44 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Leythos" <void@nowhere.org> wrote in message
news:MPG.1c035b4953c1ab79989a64@news-server.columbus.rr.com...
>
> The onboard PSU is normally not a switching unit, the Switching PSU's
> are the large metal units that you connect AC to. Most of the
> "regulators" on the motherboard have no PSU to them, they are just
> voltage regulators. A regulator, using the existing DC signal from the
> PSU, uses the CAP's to clean the ripple out of the "switched" DC supply
> from the PSU.

This is completely wrong!!!! All of the modern high-current onboard PSUs
used in digital circuits are in fact switchers. The only place where you can
still find linear regulators these days are in sensitive analog electronics.
I am a board designer myself, so I know what I am talking about. A typical
mobo will have a bunch of coils near the CPU. That's where you have a hefty
switching regulator generating CPU core voltage/voltages. If they used a
linear regulator they would have to waste half of the power since core
voltages are so low and the lowest voltage available from the big PSU is
3.3V.

/MM
Anonymous
a b V Motherboard
November 16, 2004 5:08:14 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Frank" <schmidt@bth.de> wrote in message
news:419902ad$0$154$9b622d9e@news.freenet.de...
> Now my question is: The machines work, without a flaw, beleve it or not.
> Do I have to change the mobo´s (boards) or can I stick with the present
> ones?

Find someone who is handy with a soldering iron and get him (or her) to
change the capacitors. It isn't difficult (or expensive) if you know what
you are doing - but make sure the new capacitors are the same value as the
old ones and they are installed with the polarity (+ and -) the same.

Tom S
Anonymous
a b V Motherboard
November 16, 2004 5:56:40 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <WKWdnRzKYcgNCwTcRVn-pQ@rogers.com>, mbmsv@yahoo.com says...
>
> "Leythos" <void@nowhere.org> wrote in message
> news:MPG.1c035b4953c1ab79989a64@news-server.columbus.rr.com...
> >
> > The onboard PSU is normally not a switching unit, the Switching PSU's
> > are the large metal units that you connect AC to. Most of the
> > "regulators" on the motherboard have no PSU to them, they are just
> > voltage regulators. A regulator, using the existing DC signal from the
> > PSU, uses the CAP's to clean the ripple out of the "switched" DC supply
> > from the PSU.
>
> This is completely wrong!!!! All of the modern high-current onboard PSUs
> used in digital circuits are in fact switchers. The only place where you can
> still find linear regulators these days are in sensitive analog electronics.
> I am a board designer myself, so I know what I am talking about. A typical
> mobo will have a bunch of coils near the CPU. That's where you have a hefty
> switching regulator generating CPU core voltage/voltages. If they used a
> linear regulator they would have to waste half of the power since core
> voltages are so low and the lowest voltage available from the big PSU is
> 3.3V.

He said AGP slot, not CPU area. Many of the motherboards I own and have
seen still use a number of the 3 pin regulators on them.

> If they used a
> linear regulator they would have to waste half of the power since core
> voltages are so low and the lowest voltage available from the big PSU is
> 3.3V.

What's wrong is that statement - you don't "waste" anything, the
regulator doesn't "waste" anything from the PSU. You can easily drop the
+12VDC supply down to any lower voltage without "wasting" anything.


--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
Anonymous
a b V Motherboard
November 16, 2004 6:16:05 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Leythos" <void@nowhere.org> wrote in message
news:MPG.1c03b1412e6fe94d989a65@news-server.columbus.rr.com...
> In article <WKWdnRzKYcgNCwTcRVn-pQ@rogers.com>, mbmsv@yahoo.com says...
> >
> > "Leythos" <void@nowhere.org> wrote in message
> > news:MPG.1c035b4953c1ab79989a64@news-server.columbus.rr.com...
> > >
> > > The onboard PSU is normally not a switching unit, the Switching
PSU's
> > > are the large metal units that you connect AC to. Most of the
> > > "regulators" on the motherboard have no PSU to them, they are just
> > > voltage regulators. A regulator, using the existing DC signal from
the
> > > PSU, uses the CAP's to clean the ripple out of the "switched" DC
supply
> > > from the PSU.
> >
> > This is completely wrong!!!! All of the modern high-current onboard
PSUs
> > used in digital circuits are in fact switchers. The only place where
you can
> > still find linear regulators these days are in sensitive analog
electronics.
> > I am a board designer myself, so I know what I am talking about. A
typical
> > mobo will have a bunch of coils near the CPU. That's where you have a
hefty
> > switching regulator generating CPU core voltage/voltages. If they used
a
> > linear regulator they would have to waste half of the power since core
> > voltages are so low and the lowest voltage available from the big PSU
is
> > 3.3V.
>
> He said AGP slot, not CPU area. Many of the motherboards I own and have
> seen still use a number of the 3 pin regulators on them.
Only for the +/-12v for the serial port.

> > If they used a
> > linear regulator they would have to waste half of the power since core
> > voltages are so low and the lowest voltage available from the big PSU
is
> > 3.3V.
>
> What's wrong is that statement - you don't "waste" anything, the
> regulator doesn't "waste" anything from the PSU. You can easily drop the
> +12VDC supply down to any lower voltage without "wasting" anything.
Do you understand how a linear regulator works?. If you generate a 1A 3.3v
supply from a 12v supply, using a linear regulator, you inherently have to
lose 8.8v at 1A as heat. 8.8W 'wasted'. A switching supply doing the same
job, will only typically lose perhaps half a watt. Given the current
required on the AGP supply rail (and processor supply rails) now, a system
based on linear regulators, would typically be putting over 200W out as
heat. No modern board can afford to do this, either in terms of the
temperature generated, or in terms of the actual source power available
from the supply. A common trick though is to use a 'composite' system,
with a switcher generating perhaps 5v, and then using an LDO linear
regulator from this. This is used in a few high quality boards. However
the '3 pin' devices you are seeing, are allmost certainly the switching
FETs, since the thermal limits of the TO220 package, make it unlikely to
be a linear regulator in this area.

Best Wishes
Anonymous
a b V Motherboard
November 16, 2004 6:30:45 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <VQomd.194$im.132@newsfe5-gui.ntli.net>,
rogerspamignored@ttelmah.demon.co.uk says...
> Do you understand how a linear regulator works?.

Yea, I if I take the 7812, 7805, LM317, etc... regulator device, and
look in my Linear data book, it's the same as it's been since the 80's.
The device does not disapate heat or waste anything to provide the
specified power from the supply voltage.

I don't see it as disapating anything to provide the drop to the
requested level, I see it disapating heat to provide the X volts at y
MA, through the circuit. The drop doesn't generate the heat, the load on
the regulator does.

--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
Anonymous
a b V Motherboard
November 16, 2004 6:57:32 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <MPG.1c03e7d2c54a749989a68@news-server.columbus.rr.com>,
void@nowhere.org says...
> In article <VQomd.194$im.132@newsfe5-gui.ntli.net>,
> rogerspamignored@ttelmah.demon.co.uk says...
> > Do you understand how a linear regulator works?.
>
> Yea, I if I take the 7812, 7805, LM317, etc... regulator device, and
> look in my Linear data book, it's the same as it's been since the 80's.
> The device does not disapate heat or waste anything to provide the
> specified power from the supply voltage.
>
> I don't see it as disapating anything to provide the drop to the
> requested level, I see it disapating heat to provide the X volts at y
> MA, through the circuit. The drop doesn't generate the heat, the load on
> the regulator does.

One thing to keep in mind, the OP said the cap was blown and in my
experience, if it was part of the switching power circuit, it would
almost certainly mean problems for his system.

Since he's not having any problems with it, then it must be OPEN and not
shorted and certainly not doing it's job. This leads me to believe that
it's just for filtering ripple on the board at some critical point that
requires flat voltage levels.

One last thing, if I setup a 7805 or LM317 regulator, and supply it with
12VDC and set the output to 5V, the heat generated under a 1A load is no
different than when I supply it with a 24VDC input.


--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
Anonymous
a b V Motherboard
November 16, 2004 7:34:53 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Leythos" <void@nowhere.org> wrote in message
news:MPG.1c03ee1a9bee7388989a69@news-server.columbus.rr.com...
> In article <MPG.1c03e7d2c54a749989a68@news-server.columbus.rr.com>,
> void@nowhere.org says...
> > In article <VQomd.194$im.132@newsfe5-gui.ntli.net>,
> > rogerspamignored@ttelmah.demon.co.uk says...
> > > Do you understand how a linear regulator works?.
> >
> > Yea, I if I take the 7812, 7805, LM317, etc... regulator device, and
> > look in my Linear data book, it's the same as it's been since the
80's.
> > The device does not disapate heat or waste anything to provide the
> > specified power from the supply voltage.
> >
> > I don't see it as disapating anything to provide the drop to the
> > requested level, I see it disapating heat to provide the X volts at y
> > MA, through the circuit. The drop doesn't generate the heat, the load
on
> > the regulator does.
It is the product of the current, and the voltage drop.

> One thing to keep in mind, the OP said the cap was blown and in my
> experience, if it was part of the switching power circuit, it would
> almost certainly mean problems for his system.
>
> Since he's not having any problems with it, then it must be OPEN and not
> shorted and certainly not doing it's job. This leads me to believe that
> it's just for filtering ripple on the board at some critical point that
> requires flat voltage levels.
>
> One last thing, if I setup a 7805 or LM317 regulator, and supply it with
> 12VDC and set the output to 5V, the heat generated under a 1A load is no
> different than when I supply it with a 24VDC input.
You really don't understand it do you. On a 1A load from a 12v input, a
7805, will have to dissipate 7W. From a 24v supply, it'll have to
dissipate 19W. The heat most definately _is_ different.
Anonymous
a b V Motherboard
November 16, 2004 7:34:54 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Roger Hamlett" <rogerspamignored@ttelmah.demon.co.uk> wrote in
message news:N_pmd.234$cd.93@newsfe3-gui.ntli.net...
|
| "Leythos" <void@nowhere.org> wrote in message
| news:MPG.1c03ee1a9bee7388989a69@news-server.columbus.rr.com...
| > In article
<MPG.1c03e7d2c54a749989a68@news-server.columbus.rr.com>,
| > void@nowhere.org says...
| > > In article <VQomd.194$im.132@newsfe5-gui.ntli.net>,
| > > rogerspamignored@ttelmah.demon.co.uk says...
| > > > Do you understand how a linear regulator works?.
| > >
| > > Yea, I if I take the 7812, 7805, LM317, etc... regulator device,
and
| > > look in my Linear data book, it's the same as it's been since
the
| 80's.
| > > The device does not disapate heat or waste anything to provide
the
| > > specified power from the supply voltage.
| > >
| > > I don't see it as disapating anything to provide the drop to the
| > > requested level, I see it disapating heat to provide the X volts
at y
| > > MA, through the circuit. The drop doesn't generate the heat, the
load
| on
| > > the regulator does.
| It is the product of the current, and the voltage drop.
|
| > One thing to keep in mind, the OP said the cap was blown and in my
| > experience, if it was part of the switching power circuit, it
would
| > almost certainly mean problems for his system.
| >
| > Since he's not having any problems with it, then it must be OPEN
and not
| > shorted and certainly not doing it's job. This leads me to believe
that
| > it's just for filtering ripple on the board at some critical point
that
| > requires flat voltage levels.
| >
| > One last thing, if I setup a 7805 or LM317 regulator, and supply
it with
| > 12VDC and set the output to 5V, the heat generated under a 1A load
is no
| > different than when I supply it with a 24VDC input.
| You really don't understand it do you. On a 1A load from a 12v
input, a
| 7805, will have to dissipate 7W. From a 24v supply, it'll have to
| dissipate 19W. The heat most definately _is_ different.
|
|
|

Roger is correct, a switching PS circuit is far more "efficient" than
a traditional linear regulator circuit. Roger's explanation is
technically accurate in all respects. Since the cap in issue is near
the agp slot, I suspect it is not being used in a switching PS
circuit.

A review of a LM341/7805 datasheet
http://www.national.com/ds/LM/LM341.pdf reveals the following heat
dissipation formula:

PD = (VIN-VOUT) IL + VIN*IG

PD=Power Dissipation
VIN=input voltage
VOUT=output voltage
IL= load current driven into the "load"
VIN*IG=input voltage * Ig (regulator current usage)

It should be clear that the difference between Vin and Vout directly
and linearly impacts heat dissipation in the device.
--
Best regards,
Kyle
Anonymous
a b V Motherboard
November 16, 2004 11:04:51 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <2vurf5F2rc889U1@uni-berlin.de>, me@privacy.net says...
> It should be clear that the difference between Vin and Vout directly
> and linearly impacts heat dissipation in the device.

You would think so, and technically, I agree that I'm wrong, but in
practice it does not appear so. I have the same books, even the ones
from the 80's on those devices, and they say the same thing. What I see,
in the lab does not show what the book states.

And, yes, I clearly understand that a switching PSU is more efficient
that a linear one, that was never a question.

The question is that the OP posted that a cap had burst, that the
solution had leaked, and that he noticed no difference in operation.
While I am wrong on in power dissipation, I'm not wrong in the
reason/use of the caps on the board. The caps are used to filter the
ripple out of the supply source being used on the board. Since the cap
has not caused any noticeable difference, it's safe to assume that the
cap is Open and not shorted, that he could remove it without any change
in current operation, and that it most likely has nothing to do with a
switching power circuit on the board.


--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
Anonymous
a b V Motherboard
November 17, 2004 12:39:36 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

Tom S wrote:
> Find someone who is handy with a soldering iron and get him (or her)
> to change the capacitors. It isn't difficult (or expensive) if you
> know what you are doing - but make sure the new capacitors are the
> same value as the old ones and they are installed with the polarity
> (+ and -) the same.

Or install the new capacitors with the correct polarity 'cos the original
ones may have been inserted the wrong way round which is why they leaked.
The value is not the most important factor, electrolytics have extremely
wide tolerances (-10 to 50/75%?). IMO, not fitting too high or too low a
voltage rating as a replacement is more important. Just as well that they
aren't tantalum caps - they usually go short circuit!

Regards
Anonymous
a b V Motherboard
November 17, 2004 4:02:25 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Frank" <schmidt@bth.de> wrote in message news:<419902ad$0$154$9b622d9e@news.freenet.de>...
> Hello,
>
> perhaps this is dumb, but I do not know an answer.
>
> I got 2 machines at work which work like a charm. No hangups, no bluescreen.
> Perfect.
>
> Now as I opened them for cleaning I noticed 2 capacitors with brown crusting
> on the top. Seems as they had those for a little while. Nowhere else was the
> crusting and it has dried.
>
> Now my question is: The machines work, without a flaw, beleve it or not. Do
> I have to change the mobo´s (boards) or can I stick with the present ones?
> Like never change a running system?
>
> Thanks for any advice-

If the caps are part of the switching power supply that converts the
the power supply voltages to the core voltages of the CPU, then I
doubt that your computer would still be working. However, the caps may
be filter caps that are spread around the board to provide some
additional filtering and noise reduction to the switching transients
on the ground and power planes. This is a fairly standard board design
practice. If that's the case, you'd probably never know the
difference.

arnie
Anonymous
a b V Motherboard
November 17, 2004 5:39:16 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Roger Hamlett" <rogerspamignored@ttelmah.demon.co.uk> wrote in message
news:N_pmd.234$cd.93@newsfe3-gui.ntli.net...
>> One last thing, if I setup a 7805 or LM317 regulator, and supply it with
>> 12VDC and set the output to 5V, the heat generated under a 1A load is no
>> different than when I supply it with a 24VDC input.

> You really don't understand it do you. On a 1A load from a 12v input, a
> 7805, will have to dissipate 7W. From a 24v supply, it'll have to
> dissipate 19W. The heat most definitely _is_ different.

That guy doesn't understand Ohm's law, Roger, or how linear regulators work.

Tom S
Anonymous
a b V Motherboard
November 17, 2004 6:38:55 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Tom S" <toms@dontspampacbell.net> wrote in message
news:o oJmd.22248$6q2.16034@newssvr14.news.prodigy.com...
>
> "Roger Hamlett" <rogerspamignored@ttelmah.demon.co.uk> wrote in message
> news:N_pmd.234$cd.93@newsfe3-gui.ntli.net...
> >> One last thing, if I setup a 7805 or LM317 regulator, and supply it
with
> >> 12VDC and set the output to 5V, the heat generated under a 1A load is
no
> >> different than when I supply it with a 24VDC input.
>
> > You really don't understand it do you. On a 1A load from a 12v input,
a
> > 7805, will have to dissipate 7W. From a 24v supply, it'll have to
> > dissipate 19W. The heat most definitely _is_ different.
>
> That guy doesn't understand Ohm's law, Roger, or how linear regulators
work.
Either that, or he has managed to invent perpetual motion by a
'roundabout' method (if the regulator still generates the same heat in the
lower voltage feed case, with the same load, he is getting power from
nowhere.... :-)

Best Wishes
Anonymous
a b V Motherboard
November 17, 2004 9:12:12 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <ooJmd.22248$6q2.16034@newssvr14.news.prodigy.com>,
toms@dontspampacbell.net says...
>
> "Roger Hamlett" <rogerspamignored@ttelmah.demon.co.uk> wrote in message
> news:N_pmd.234$cd.93@newsfe3-gui.ntli.net...
> >> One last thing, if I setup a 7805 or LM317 regulator, and supply it with
> >> 12VDC and set the output to 5V, the heat generated under a 1A load is no
> >> different than when I supply it with a 24VDC input.
>
> > You really don't understand it do you. On a 1A load from a 12v input, a
> > 7805, will have to dissipate 7W. From a 24v supply, it'll have to
> > dissipate 19W. The heat most definitely _is_ different.
>
> That guy doesn't understand Ohm's law, Roger, or how linear regulators work.

Sure I do, but I don't have to live in theory only, try it some time.
Take a regulator of your choice, the 7805 is a nice package, use an
input voltage of 24VDC and then 12VDC with a load of 500ma on the 5v
side - you won't notice the difference in temp.

--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
November 17, 2004 9:12:13 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

> Sure I do, but I don't have to live in theory only, try it some time.
> Take a regulator of your choice, the 7805 is a nice package, use an
> input voltage of 24VDC and then 12VDC with a load of 500ma on the 5v
> side - you won't notice the difference in temp.

Sure, you don't. 7805 will either blow up or will go into internal thermal
protection mode should you put it into such a circuit. It is a 100 mA
regulator and there is no way it can dissipate (24-5)*0.5=9.5W of power or
even 3.5W in case of 12V input.... Sorry.

/MM
Anonymous
a b V Motherboard
November 18, 2004 12:00:36 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <301q2dF2pdul4U1@uni-berlin.de>, mbmsv@yahoo.com says...
> > Sure I do, but I don't have to live in theory only, try it some time.
> > Take a regulator of your choice, the 7805 is a nice package, use an
> > input voltage of 24VDC and then 12VDC with a load of 500ma on the 5v
> > side - you won't notice the difference in temp.
>
> Sure, you don't. 7805 will either blow up or will go into internal thermal
> protection mode should you put it into such a circuit. It is a 100 mA
> regulator and there is no way it can dissipate (24-5)*0.5=9.5W of power or
> even 3.5W in case of 12V input.... Sorry.

Try again, the LM7805 will handle 1A if properly heatsinked.
http://www.national.com/pf/LM/LM7805C.html


--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
November 18, 2004 12:00:37 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

> Try again, the LM7805 will handle 1A if properly heatsinked.
> http://www.national.com/pf/LM/LM7805C.html

OK, I was looking at LM78L05, which is a lower power version of the LM7805.
With the original LM7805 you might be able to actually dissipate your 9.5W,
but take a look at the Maximum Power Dissipation graphs in the datasheet, it
will only work with a hefty heatsink or in a fridge. The bigger device
doesn't change the basics of the Ohm's law. It is actually bigger because of
these basics!


/MM
Anonymous
a b V Motherboard
November 18, 2004 12:50:34 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <301uugF2rhsgmU1@uni-berlin.de>, mbmsv@yahoo.com says...
> > Try again, the LM7805 will handle 1A if properly heatsinked.
> > http://www.national.com/pf/LM/LM7805C.html
>
> OK, I was looking at LM78L05, which is a lower power version of the LM7805.
> With the original LM7805 you might be able to actually dissipate your 9.5W,
> but take a look at the Maximum Power Dissipation graphs in the datasheet, it
> will only work with a hefty heatsink or in a fridge. The bigger device
> doesn't change the basics of the Ohm's law. It is actually bigger because of
> these basics!

In looking at the T0-3 unit, with heat-sink, sitting near my desk in a
power supply, and another one with the TO-220 style package, with heat-
sink, also sitting here (since I have about 30 of the 7805 devices and
another 10 LM338 and 317's and a bunch of power transistors and others.
I can assure you that the TO-3 and TO-220 units can deliver a sustained
500MA draw with little problem using a normal heat-sink (even one from
RadioShack) and a minimal amount of HSP.

They can also provide a sustained 1A of power, but, with a standard
heat-sink, you do notice a little heat from the fins. I would imagine if
you were to push beyond 1A a cooling fan might be required.


--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
November 18, 2004 12:50:35 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

> I can assure you that the TO-3 and TO-220 units can deliver a sustained
> 500MA draw with little problem using a normal heat-sink (even one from
> RadioShack) and a minimal amount of HSP.

I've no doubt it can deliver 500 mA, the question is how big a voltage drop
it can handle with this load. Somehow you don't want to admit the obvious.
The maximum junction temperature for both of these cases (TO3 and TO220) is
150 C. The junction-to-case thermal resistance is 4 C/W. Assuming your
heatsink has 10C/W resistance to ambient (which is pretty good) we get 14
C/W junction-to-ambient minimum resistance. At 9.5W of power dissipation
you'll have 9.5*14=133 C temperature differential between the junction and
ambient. Since the temperature in a computer case is usually higher than in
a room, let's say 35 C, you will have your junction at 168 C, which is well
above the spec. Do you still want to try 1 A at 24VDC input (19W to
dissipate)? Let us know how well it worked.


/MM
November 18, 2004 1:38:45 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

> If the caps are part of the switching power supply that converts the
> the power supply voltages to the core voltages of the CPU, then I
> doubt that your computer would still be working. However, the caps may
> be filter caps that are spread around the board to provide some
> additional filtering and noise reduction to the switching transients
> on the ground and power planes. This is a fairly standard board design
> practice. If that's the case, you'd probably never know the
> difference.
>


Thanks for all the answers. As for now I´m no good at soldering, I have no
warranty on these 2 machines. I got 2 spare boards in the closet, so I´m set
for all things that can happen. As the still work like a charm I´m not doing
anything by now. Thanks for all the help, again.

Frank
November 18, 2004 1:39:40 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

.. Wenn nicht, arbeite
> solange es geht mit dem Board weiter und tausch es gegen ein Neues aus,
> sobald Fehler auftreten.
>
Hallo Carsten,

danke für die Hilfe, und genau das werde ich tun.

Gruß

Frank
Anonymous
a b V Motherboard
November 18, 2004 3:38:41 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <30216dF2og258U1@uni-berlin.de>, mbmsv@yahoo.com says...
> > I can assure you that the TO-3 and TO-220 units can deliver a sustained
> > 500MA draw with little problem using a normal heat-sink (even one from
> > RadioShack) and a minimal amount of HSP.
>
> I've no doubt it can deliver 500 mA, the question is how big a voltage drop
> it can handle with this load. Somehow you don't want to admit the obvious.
> The maximum junction temperature for both of these cases (TO3 and TO220) is
> 150 C. The junction-to-case thermal resistance is 4 C/W. Assuming your
> heatsink has 10C/W resistance to ambient (which is pretty good) we get 14
> C/W junction-to-ambient minimum resistance. At 9.5W of power dissipation
> you'll have 9.5*14=133 C temperature differential between the junction and
> ambient. Since the temperature in a computer case is usually higher than in
> a room, let's say 35 C, you will have your junction at 168 C, which is well
> above the spec. Do you still want to try 1 A at 24VDC input (19W to
> dissipate)? Let us know how well it worked.

While you won't like my answer, and I'm sure you say it's not true, I've
been doing it for years. Almost always use +24 to the supply side for
the +15, +10, +5 supply circuits, and -24 for the -15, -10 circuits. The
have handled 500MA loads for years with the standard heat-sink and HSP.

You and I can both read the spec's, and I have never disagreed with
them, not once, but what works in the real world is different that the
specs many times. Heck, I even have one +/- 15vdc follower that I built
in the early 80's that still works (changed the caps a few years back),
and it still follows within about 3mv all day long.

--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
November 18, 2004 3:38:42 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Leythos" <void@nowhere.org> wrote in message
news:MPG.1c05bb2aa1024f3b989a7c@news-server.columbus.rr.com...
>
> While you won't like my answer, and I'm sure you say it's not true, I've
> been doing it for years. Almost always use +24 to the supply side for
> the +15, +10, +5 supply circuits, and -24 for the -15, -10 circuits. The
> have handled 500MA loads for years with the standard heat-sink and HSP.

You are a strange person I should say. There is a huge difference between
15V and 5V output in this case! With 5V at 500mA you are on the edge of what
can be done with a 7805. At 15V you do have some margin.

> You and I can both read the spec's, and I have never disagreed with
> them, not once, but what works in the real world is different that the
> specs many times.

If this happens, it usually means either error in measurements or in how
these measurements are being interpreted. Besides, this time you are
challenging much more than a spec, you are challenging one of the basic laws
of physics.

/MM
Anonymous
a b V Motherboard
November 18, 2004 7:16:34 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <302gr6F2ptuihU1@uni-berlin.de>, mbmsv@yahoo.com says...
> "Leythos" <void@nowhere.org> wrote in message
> news:MPG.1c05bb2aa1024f3b989a7c@news-server.columbus.rr.com...
> >
> > While you won't like my answer, and I'm sure you say it's not true, I've
> > been doing it for years. Almost always use +24 to the supply side for
> > the +15, +10, +5 supply circuits, and -24 for the -15, -10 circuits. The
> > have handled 500MA loads for years with the standard heat-sink and HSP.
>
> You are a strange person I should say. There is a huge difference between
> 15V and 5V output in this case! With 5V at 500mA you are on the edge of what
> can be done with a 7805. At 15V you do have some margin.

Maybe I should have been more clear - the +15 and +10 are not done with
the LM78XX series. The 5V is and works fine, even at loads of 1A over
hours of continuous operation.

> > You and I can both read the spec's, and I have never disagreed with
> > them, not once, but what works in the real world is different that the
> > specs many times.
>
> If this happens, it usually means either error in measurements or in how
> these measurements are being interpreted. Besides, this time you are
> challenging much more than a spec, you are challenging one of the basic laws
> of physics.

Ah, the old, specs could be wrong, physics could be wrong, something
must be wrong, cause you can't explain how it can work on paper when it
works in real life.

Here's and Idea, instead of telling me something that I'm doing can't be
done, that the spec's don't allow for it, try it yourself, the LM7805C's
are cheap, pick your package type, and try it - just try it yourself
before you tell me what I'm doing isn't possible.

--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
November 18, 2004 7:16:35 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Leythos" <void@nowhere.org> wrote in message
news:MPG.1c05ee3e50bc0dc9989a7e@news-server.columbus.rr.com...
works in real life.
>
> Here's and Idea, instead of telling me something that I'm doing can't be
> done, that the spec's don't allow for it, try it yourself, the LM7805C's
> are cheap, pick your package type, and try it - just try it yourself
> before you tell me what I'm doing isn't possible.

I am doing this kind of thing pretty much every day. That's what I am being
paid to do. So far, I haven't been able to break the Ohm's law. Why don't
YOU try to load your perpetum mobile with a 5A load and feed it with 100VDC.
It shouldn't make any difference in heat, right? Go and measure your
voltages, currents and temperatures properly and then we can see whether
theory is coherent with practice.

/MM
Anonymous
a b V Motherboard
November 18, 2004 2:47:54 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <Up-dnQw5WtrnpAHcRVn-pg@rogers.com>, mbmsv@yahoo.com says...
> "Leythos" <void@nowhere.org> wrote in message
> news:MPG.1c05ee3e50bc0dc9989a7e@news-server.columbus.rr.com...
> works in real life.
> >
> > Here's and Idea, instead of telling me something that I'm doing can't be
> > done, that the spec's don't allow for it, try it yourself, the LM7805C's
> > are cheap, pick your package type, and try it - just try it yourself
> > before you tell me what I'm doing isn't possible.
>
> I am doing this kind of thing pretty much every day. That's what I am being
> paid to do. So far, I haven't been able to break the Ohm's law. Why don't
> YOU try to load your perpetum mobile with a 5A load and feed it with 100VDC.
> It shouldn't make any difference in heat, right? Go and measure your
> voltages, currents and temperatures properly and then we can see whether
> theory is coherent with practice.

I hear that same rhetoric from people all the time. I don't care if
you're paid to do it, like that means your qualified. I don't care if
you just want to whine about it not being possible. I don't care if you
don't seem to understand that it's already being done and working. I've
been building power supply units since the 70's, and unlike you, I've
not been blinded by the "I can only do what the spec's say I can do"
mentality.

Like I said, try it yourself, put aside your big headed idea that it's
not possible, just try it, you might surprise yourself. What I've seen
from your replies is symptomatic of the typical "the spec's say it can't
work, so it can't work type of people". Open your eyes once and quit
being such a closed minded person and just try it, it's a simple
circuit, you should be able to build it in under an hour (even if you
have to solder it yourself). You might even have the parts, since you're
pretty much paid to do this this every day - if you don't have the TO-3
LM7805 you can order one for about $5 from suppliers.

One of these days you might want to actually try something before you
speak out that it's impossible, when you do try it you're going to look
funny posting that it did work (not that I expect that from someone like
you).


--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
November 18, 2004 2:47:55 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Leythos" <void@nowhere.org> wrote in message
news:MPG.1c0656948ac2f4fd989a80@news-server.columbus.rr.com...
>
> Like I said, try it yourself, put aside your big headed idea that it's
> not possible, just try it, you might surprise yourself.
>
You are not hearing me. I am trying this kind of thing every day and I am
not seeing the results you see. If you want me to try something be more
specific. What it is precisely you want me to try and what it is I will see?
What are the design goals/parameters:

Input voltage, load, max and min ambient temperature, heat sink thermal
resistance, etc?

/MM
Anonymous
a b V Motherboard
November 18, 2004 10:14:33 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <WcudnZu1PdTDOwHcRVn-1Q@rogers.com>, mbmsv@yahoo.com says...
> "Leythos" <void@nowhere.org> wrote in message
> news:MPG.1c0656948ac2f4fd989a80@news-server.columbus.rr.com...
> >
> > Like I said, try it yourself, put aside your big headed idea that it's
> > not possible, just try it, you might surprise yourself.
> >
> You are not hearing me. I am trying this kind of thing every day and I am
> not seeing the results you see. If you want me to try something be more
> specific. What it is precisely you want me to try and what it is I will see?
> What are the design goals/parameters:
>
> Input voltage, load, max and min ambient temperature, heat sink thermal
> resistance, etc?

Here's what you've said:

Based on the spec's, the LM7805 can not provide reliable output of 5v at
500MA (or even 1A) with a standard heat sink with an supply voltage of
24VDC.

I said:

Wrong, it works, is working, and has worked on many systems for at least
about 20 years that I know of and have DIRECT experience with. I also
said that I have read and understand the technical specs, but that
sometimes you have to just believe what you see in the real world and
not just on paper.

I think you can figure out what you have to test based on the two
statements above.

--
--
spamfree999@rrohio.com
(Remove 999 to reply to me)
November 18, 2004 10:14:34 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Leythos" <void@nowhere.org> wrote in message
news:MPG.1c06bf4f8b968e0989a82@news-server.columbus.rr.com...
>
> Here's what you've said:
>
> Based on the spec's, the LM7805 can not provide reliable output of 5v at
> 500MA (or even 1A) with a standard heat sink with an supply voltage of
> 24VDC.
>
> I said:
>
> Wrong, it works, is working, and has worked on many systems for at least
> about 20 years that I know of and have DIRECT experience with. I also
> said that I have read and understand the technical specs, but that
> sometimes you have to just believe what you see in the real world and
> not just on paper.
>
> I think you can figure out what you have to test based on the two
> statements above.

1. What the hell is a "standard" heatsink?
2. What is the ambient temperature?

I don't have more time to spend on this BS. I've done my labs to prove the
Ohm's law many years ago in Grade 7 or 8. There is nothing to be gained from
this experiment. The last board I designed has 5 switching regulators and
over a dozen of linear ones. Every and each of them work according to the
known laws of physics and dissipate precisely the amount of heat I
calculated. Yes, you can run semiconductors at 150C or some even higher, but
reliable things are not designed this way. Have you ever heard of derating?
Have you ever seen a curve demonstrating failure frequency depending on
junction temperature? As I can see it, you look at a datasheet, notice the
max current and max input voltage and then you plug it in a circuit and
experiment. You might be lucky and it "works" most of the times, but have
you tried to qualify your circuit to work in avionics equipment where
ambient temperatures can easily reach 70 C and where cooling air coming from
a fan is sometimes just as hot? If people were doing designs your way we
would still be in a crystal radio age. Why do you believe the output voltage
spec and don't believe power and temperature rating specs? You don't expect
to see 7V or 17V output from your favorite 7805, but somehow you expect that
other parts of the spec along with fundamental laws of physics can be
stretched to whatever lengths. Finally, back to your 500mA 24VDC PSU. I
didn't say it can't work, but it is on the edge depending on your heatsink.
If you increase the current to 1A it will most likely fail (again depending
on the heatsink, ambient temperature and fan speed).

/MM


/MM
Anonymous
a b V Motherboard
November 19, 2004 12:10:27 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <304g0cF2rjqo9U1@uni-berlin.de>, mbmsv@yahoo.com says...
> 1. What the hell is a "standard" heatsink?

Something you can find for sale in the common electronics supply
catalogs - not something that is the size of a Refrige.

> 2. What is the ambient temperature?

Room temp, don't ask what room, pick one in your house, on a normal day.

> I don't have more time to spend on this BS. I've done my labs to prove the
> Ohm's law many years ago in Grade 7 or 8. There is nothing to be gained from
> this experiment.

Sure there is, but, as I figured, you don't like to be wrong, so you
absolve yourself of it by saying that your labs and specs are right.

> The last board I designed has 5 switching regulators and
> over a dozen of linear ones. Every and each of them work according to the
> known laws of physics and dissipate precisely the amount of heat I
> calculated.

And I never suggested that your designs don't work, never suggested that
Ohms law was wrong, or anything of the sort. If you want to boast about
your abilities, I was doing the above in the late 70's, and still have
parts cabinets full of chips - but who cares.

If you are going to make a statement that the LM7805 can not operate at
5V providing 500MA in a stable configuration with a supply voltage of +
24V then you ought to be able to prove it. I did, it works, got a couple
of them right here, working for years. I'm not asking you to take my
word for it alone, I'm saying that it works, is stable, and does not
fail, and that if you don't believe it, try it yourself. If you can't be
big enough to at least try it, then quit whining about how it can't
work!


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Anonymous
a b V Motherboard
November 19, 2004 3:40:49 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

Re: "The onboard PSU is normally not a switching unit, the Switching
PSU's are the large metal units that you connect AC to."

That is totally wrong. The Vcore power supply for the CPU, which is on
the motherboard, most definitely IS a switching power supply.

The correct advice here is to remove AND REPLACE the bad capacitors.
Frankly, I'd replace any other SIMILAR capacitors at the same time.
About 2-3 years ago, the industry was flooded with several hundred
million bad electrolytic capacitors. It happened because a chemical
company that was going bankrupt, in an attempt to save money, left a
critical but expensive chemical out of their production of electrolyte
used by the capacitor makers in Taiwan. I'm guessing that you have some
of those caps.

There really is no solution other than to remove and replace them, which
will require soldering. You don't need an exact replacement. If in
doubt, get parts with higher capacitance and/or higher voltage. I have
an oscilloscope that I built in 1980 that I was into to replace a pilot
lamp, and I noticed a 3000 uF 15 volt capacitor blown completely apart,
the scope worked fine without it. I temporarily replaced it with a 1000
uf 25 volt part (closest I could come at radio shack), but later
installed a 3000 uf 30 volt part.


Leythos wrote:
> In article <dqWdndAEi68TEATcRVn-1Q@rogers.com>, mbmsv@yahoo.com says...
>
>>"Leythos" <void@nowhere.org> wrote in message
>>news:MPG.1c02dd7c4ad1dc9c989a57@news-server.columbus.rr.com...
>>
>>>Replace the CAP as soon as possible or at least remove it.
>>
>>Removing a cap from a switching power supply, where it is likely to belong,
>>might disable the board completely. I actually found a similar problem on my
>>old Aopen mobo (in my case the caps are definitely belong to the main CPU
>>switching power supply), so I went and bought a new ASUS mobo :)  But I am
>>going to replace the caps on the old board and then build a second computer.
>
>
> The onboard PSU is normally not a switching unit, the Switching PSU's
> are the large metal units that you connect AC to. Most of the
> "regulators" on the motherboard have no PSU to them, they are just
> voltage regulators. A regulator, using the existing DC signal from the
> PSU, uses the CAP's to clean the ripple out of the "switched" DC supply
> from the PSU.
>
> Removing a CAP, from the PSU would indeed cause problems, as they use
> the caps to provide ripple rejection to the DC output.
>
> The caps on a motherboard, in almost every instance, are to spot signal
> filtering or for ripple rejection at the point.
>
Anonymous
a b V Motherboard
November 19, 2004 3:49:39 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

The first poster was correct. Linear regulators, including 3-terminal
regulators like 7805's, drop the voltage by WASTING the excess as heat.
Essentially, they drop the voltage by putting an electronically
variable resistance between the higher voltage and the desired lower
voltage.

Say you are using a 7805 to drop 12 volts (which might be unregulated as
well) down to 5 volts. The extra 7 volts is across the 7805. If the
current draw at 5 volts is 100ma (0.1 amps), then you are "wasting" .7
watts in the regulator (7 volts across the regulator x .1 amps through
the regulator). That might not sound like much, but the load is only
using .5 watts (5 volts, 0.1 amps), so you are "wasting" more than you
are using. The wasted power appears as heat (the regulator gets hot,
and may require a heat sink).

3 terminal regulators can only dissipate about 2-3 watts total at most,
and only then with a good heat sink. So while a 7805 can supply 1 amp,
you can forget about it if you want to drop 24 volts to 5 volts, because
it would have to dissipate 19 watts (1 amp, 19 volts across the
regulator). On the other hand, if you were working from an 8 volt
supply, it could handle it, because the power dissipation would now only
be 3 watts (near the limit of the regulator, but manageable with a good
heat sink).

The whole reason for using a switching regulator is that they have high
efficiency, they don't waste power. That's because they don't "drop"
the output voltage from the input voltage, rather they generate the
output voltage "from scratch".


>
>>If they used a
>>linear regulator they would have to waste half of the power since core
>>voltages are so low and the lowest voltage available from the big PSU is
>>3.3V.
>
>
> What's wrong is that statement - you don't "waste" anything, the
> regulator doesn't "waste" anything from the PSU. You can easily drop the
> +12VDC supply down to any lower voltage without "wasting" anything.
>
>
Anonymous
a b V Motherboard
November 19, 2004 3:50:33 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

Leythos, you are just totally wrong, and have no understanding of how
these parts work.


Leythos wrote:

> In article <VQomd.194$im.132@newsfe5-gui.ntli.net>,
> rogerspamignored@ttelmah.demon.co.uk says...
>
>>Do you understand how a linear regulator works?.
>
>
> Yea, I if I take the 7812, 7805, LM317, etc... regulator device, and
> look in my Linear data book, it's the same as it's been since the 80's.
> The device does not disapate heat or waste anything to provide the
> specified power from the supply voltage.
>
> I don't see it as disapating anything to provide the drop to the
> requested level, I see it disapating heat to provide the X volts at y
> MA, through the circuit. The drop doesn't generate the heat, the load on
> the regulator does.
>
Anonymous
a b V Motherboard
November 19, 2004 3:58:08 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

The cap is probably neither open nor shorted, in fact it's quite
possibly still working .... as a capacitor.

The problem with the defective electrolyte that was used in a few
hundred million capacitors made a couple years ago was that a chemical
that reduced "gassing" was left out. The capacitors then could produce
excessive gas pressure and eventually the "can" would ruture somewhere.

While this can destroy the capacitor in either an open or a short mode,
sometime all that happens is that the can ruptures, electrolyte leaks
out, but the capacitor basically isn't catastrophically destroyed (at
least not immediately).

The loss of electrolyte will reduce the effective capacitance of the
capacitor, but this normally isn't critical until towards the end (when
either most of the electrolyte has leaked out or dried out). Also, as
was noted, the electrolyte is corrosive and can "eat through" the traces
on the circuit board. The capacitor should be replaced, but IN THIS
INSTANCE, it may well have neither shorted nor opened, and may, for the
moment, still be functioning "adequately".

[One other possibility is that it IS open, but these circuits often have
quite a few capacitors in parallel, and the remaining capacitors (which
have not failed YET) may be adequate to keep things working ok.]


>
> One thing to keep in mind, the OP said the cap was blown and in my
> experience, if it was part of the switching power circuit, it would
> almost certainly mean problems for his system.
>
> Since he's not having any problems with it, then it must be OPEN and not
> shorted and certainly not doing it's job. This leads me to believe that
> it's just for filtering ripple on the board at some critical point that
> requires flat voltage levels.
>
> One last thing, if I setup a 7805 or LM317 regulator, and supply it with
> 12VDC and set the output to 5V, the heat generated under a 1A load is no
> different than when I supply it with a 24VDC input.
>
>
Anonymous
a b V Motherboard
November 19, 2004 4:10:58 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

First, you are wrong both in theory and in practice. A 7805 dropping 12
volts to 5 will dissipate more than twice as much power (heat) as one
dropping 8 volts to 5 (assuming the same current draw). And the
difference is VERY, VERY real.

Second, actually, the capacitor is NOT necessarily being used as a
ripple filter here, but rather as an "energy storage reservoir". There
is no ripple in the output of a linear regulator whose input is DC. And
while the output of a switching power supply would have ripple, the
frequency is VERY high (80-120 KHz is a common range) and is easily
filtered with small, tiny capacitors.

The reason for the large electrolytic caps is the same as the reason for
using 1 FARAD $200 capacitors in ultra-powerful automotive stereo
systems (the ones that you can FEEL when the guy whose car it's in parks
next to you). The reason is that the peak, instantaneous current
requirements of some modern CPU and video chips is tremendous. Some
Pentium 4's have peak Vcore current requirements in excess of 70 amps.
But these peaks last for nanoseconds or microseconds. The power
supplies, by themselves, can't supply that kind of power, and the large
electrolytic caps are present meet these demands, not to filter ripple.


Leythos wrote:

> In article <2vurf5F2rc889U1@uni-berlin.de>, me@privacy.net says...
>
>>It should be clear that the difference between Vin and Vout directly
>>and linearly impacts heat dissipation in the device.
>
>
> You would think so, and technically, I agree that I'm wrong, but in
> practice it does not appear so. I have the same books, even the ones
> from the 80's on those devices, and they say the same thing. What I see,
> in the lab does not show what the book states.
>
> And, yes, I clearly understand that a switching PSU is more efficient
> that a linear one, that was never a question.
>
> The question is that the OP posted that a cap had burst, that the
> solution had leaked, and that he noticed no difference in operation.
> While I am wrong on in power dissipation, I'm not wrong in the
> reason/use of the caps on the board. The caps are used to filter the
> ripple out of the supply source being used on the board. Since the cap
> has not caused any noticeable difference, it's safe to assume that the
> cap is Open and not shorted, that he could remove it without any change
> in current operation, and that it most likely has nothing to do with a
> switching power circuit on the board.
>
>
November 19, 2004 4:37:55 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

"Leythos" <void@nowhere.org> wrote in message
news:MPG.1c06da7b78658b87989a86@news-server.columbus.rr.com...
>
> If you are going to make a statement that the LM7805 can not operate at
> 5V providing 500MA in a stable configuration with a supply voltage of +
> 24V then you ought to be able to prove it.

I haven't made this statement. I believe it will work in a room temperature
with an adequate heatsink. Are you happy now? However, using a linear
regulator this way is generally a bad design practice these days unless
there are very strong reasons for it.

I think we should stop here. This is way OT for this newsgroup. It should be
moved to the sci.electronics.basics should you wish to continue.

/MM
Anonymous
a b V Motherboard
November 19, 2004 5:12:38 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <419D4570.50807@neo.rr.com>, WatzmanNOSPAM@neo.rr.com says...
> Leythos, you are just totally wrong, and have no understanding of how
> these parts work.

Um, lets see - build 24V DC output, connect to basic LM7805 circuit,
load to 500MA, leave loaded and running for weeks. Leave DVM connected
to PC tracking output in 30 second intervals over 12 hour period, record
shows stable output at each point - logged data represents real world
experience.

So, what part am I missing? It seems to me that while no one here is
arguing the specs, the physics behind it, or the heat, that what you are
failing to understand is that it's working, running fine, and has worked
for many years. I can't make it any simpler for you, it just works!


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Anonymous
a b V Motherboard
November 19, 2004 6:46:24 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

Linear regulators (eg Series 80nn) MAY waste huge amount of power
(power means watts or volt-amps or whatever you understand)..under
several situations.

If the diff. between Vin and Vout is significant...I'l use the text
book case where it specifies that Vin should be at least 3 volts over
the desired Vout.

The regulation can and will generate tons of heat...but this is reated
to the current (A) being drawn by the load connected to Vout.

If, forexample, you use a TO-220 package 7805 regulator, and feed it
say 9volts and consume ~ 1A@ 5Volts...you'll feel some real heat!!!

That's why the databooks indicate heatsink requiremnets and so
forth...Linear regulators...under real load...are not very efficient
and the lost efficiency makes heat!!







On Tue, 16 Nov 2004 16:34:53 GMT, "Roger Hamlett"
<rogerspamignored@ttelmah.demon.co.uk> wrote:

>
>"Leythos" <void@nowhere.org> wrote in message
>news:MPG.1c03ee1a9bee7388989a69@news-server.columbus.rr.com...
>> In article <MPG.1c03e7d2c54a749989a68@news-server.columbus.rr.com>,
>> void@nowhere.org says...
>> > In article <VQomd.194$im.132@newsfe5-gui.ntli.net>,
>> > rogerspamignored@ttelmah.demon.co.uk says...
>> > > Do you understand how a linear regulator works?.
>> >
>> > Yea, I if I take the 7812, 7805, LM317, etc... regulator device, and
>> > look in my Linear data book, it's the same as it's been since the
>80's.
>> > The device does not disapate heat or waste anything to provide the
>> > specified power from the supply voltage.
>> >
>> > I don't see it as disapating anything to provide the drop to the
>> > requested level, I see it disapating heat to provide the X volts at y
>> > MA, through the circuit. The drop doesn't generate the heat, the load
>on
>> > the regulator does.
>It is the product of the current, and the voltage drop.
>
>> One thing to keep in mind, the OP said the cap was blown and in my
>> experience, if it was part of the switching power circuit, it would
>> almost certainly mean problems for his system.
>>
>> Since he's not having any problems with it, then it must be OPEN and not
>> shorted and certainly not doing it's job. This leads me to believe that
>> it's just for filtering ripple on the board at some critical point that
>> requires flat voltage levels.
>>
>> One last thing, if I setup a 7805 or LM317 regulator, and supply it with
>> 12VDC and set the output to 5V, the heat generated under a 1A load is no
>> different than when I supply it with a 24VDC input.
>You really don't understand it do you. On a 1A load from a 12v input, a
>7805, will have to dissipate 7W. From a 24v supply, it'll have to
>dissipate 19W. The heat most definately _is_ different.
>
>
Anonymous
a b V Motherboard
November 19, 2004 2:38:55 PM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

In article <305im6F2taohgU1@uni-berlin.de>, mbmsv@yahoo.com says...
> I believe it will work in a room temperature
> with an adequate heatsink.

I agree.

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Anonymous
a b V Motherboard
November 20, 2004 4:23:32 AM

Archived from groups: alt.comp.periphs.mainboard.asus (More info?)

I suspect that what you think is happening, really isn't.

If you are getting 5 volts from a 7805 whose input is 24 volts, there is
19 volts across the 7805. That's not speculation or theory -- it's
simple physics, e.g. it's both theory AND real-world practice.

If you are pulling 500ma through ANY device with 19 volts across it,
it's GOING to dissipate 9.5 watts. Again, that's not speculation or
theory -- it's simple physics, e.g. it's both theory AND real-world
practice.

You can't dissipate 9.5 watts in a device the size of a 7805 without
some serious thermal considerations (and you may not be able to do it at
all, period).

My suggestion is that either the voltage or the current are not what you
say they are (or even believe that they are), or that you are just
making this up and have not really tried it.

[which, among other things, leaves me wondering if you know how to use a
multi-meter, especially to measure current]


Leythos wrote:

> In article <419D4570.50807@neo.rr.com>, WatzmanNOSPAM@neo.rr.com says...
>
>>Leythos, you are just totally wrong, and have no understanding of how
>>these parts work.
>
>
> Um, lets see - build 24V DC output, connect to basic LM7805 circuit,
> load to 500MA, leave loaded and running for weeks. Leave DVM connected
> to PC tracking output in 30 second intervals over 12 hour period, record
> shows stable output at each point - logged data represents real world
> experience.
>
> So, what part am I missing? It seems to me that while no one here is
> arguing the specs, the physics behind it, or the heat, that what you are
> failing to understand is that it's working, running fine, and has worked
> for many years. I can't make it any simpler for you, it just works!
>
>
!