From: Marco Mailand (marco.mailand_at_gmail.com)
Date: Thu Dec 29 2005 - 23:25:08 PST
2005/12/30, James Wages <james_at_kiramek.com>:
> On 12/30/05 11:53 AM, Andrei Chichak <newton_at_chichak.ca> wrote:
> > Electrolytic capacitors do dry out...
> So unless you understand
> what type is needed in a particular design, replace with the same type
> capacitor.
The ElCos do not only dry out. We had 14 IBM desktop PCs (NetVista
M40, 866MHz) which reached their end of lease age (about 3 years +)
and which stopped working just a few weeks before the replacement day
with the reboot symptom. Because it just was the same time of one of
these big reboot virus attacks and it was fact that our IT-people
didn't approved the latest virus scan patch for about 10 days, we
checked the HD's of the defect NetVistas for the reboot virus. But
nope, there was none. A comparison of the Mobo's of all 14 machines
after the replacement showed that the 3 rebooting ones had each
between 2 to 6 cracked Elcos, just next to the processor cooler.
We replaced the first row Elcos (9 pcs) and can use the machines since
then w/o any problems nor reinstallation of the system or the like.
Finally I spoke with a colleague from one of our subsidaries in Sweden
and he confirmed exactly the same.
It is very likely that the Elcos cracked because of overheating due to
the proximity to the processor cooler. We measured their voltage but
it was with 2.7V way below the rated 10V. The detection of a defective
Elco or the proof of its failure is also not that easy because they
often do not have a hard short or change their electric behaviour if
they get exposed to voltage or get warm.
There is a lot of interesting side considerations to be aware off when
constructing proper electronics and even a big brand manufacurer may
fail. So don't trust anyone and nothing.
For the Newton we have one very positive thing to be mentioned: No
mechanically moving parts.
(I'm just now plagued by dying harddrives anywhere... :-( and what
coincidence: All made by IBM.)
Marco
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