Capacitor

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-

"Frank" wrote in message
...
| 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

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

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.

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

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

"Leythos" wrote in message
...

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

"Leythos" wrote in message
...

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

"Frank" wrote in message
...
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

"Leythos" wrote in message
...
In article , says...

"Leythos" wrote in message
...

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