10 Feb
2003
10 Feb
'03
4:52 a.m.
From: "Bryan Pope"
<bpope(a)wordstock.com>
Hey all,
Awhile ago there was a thread about electrolytic capacitors popping and
then destroying the motherboard they are on. One of the ideas was to
replace them before they go.
Now I was wondering about another idea... Would it be okay to encase
the capacitor in silicone gel? Then when the capacitor pops, it wouldn't
spread its electrolyte all over the motherboard.
But would this cause other problems with heat or something? Would it
further shorten the life of the capacitor?
Cheers,
Bryan
Hi
There isn't much you could cover it with that would stop a cap
from blowing. The pressures can get to several thousand
PSI
if there isn't a relief someplace. Wrapping several layers of
paper towel around them might be better. This would at least
keep the mess from the PCB.
There was an article about some bad capacitors made in the
last few years. According to the story, someone stole a formula
for the electrolyte and the formula was missing some key
ingredient ( most likely a depolarizer ). The caps made this
way would out gas and rupture.
Dwight
10 Feb
10 Feb
5:16 a.m.
On Mon, 10 Feb 2003, Dwight K. Elvey wrote:
Why not just cover the cap with heat-shrink tubing? I've seen this done
quite a bit in high end switching power supplies. They often have about
3/8-1/2" extra sticking up from the top of the cap.
-Toth
Awhile ago
there was a thread about electrolytic capacitors popping
and then destroying the motherboard they are on. One of the ideas was
to replace them before they go.
Now I was wondering about another idea... Would it be okay to encase
the capacitor in silicone gel? Then when the capacitor pops, it
wouldn't spread its electrolyte all over the motherboard.
But would this cause other problems with heat or something? Would it
further shorten the life of the capacitor?
There isn't much you could cover it with that would stop a cap from
blowing. The pressures can get to several thousand PSI if there isn't a
relief someplace. Wrapping several layers of paper towel around them
might be better. This would at least keep the mess from the PCB.
There was an article about some bad capacitors made in the last few
years. According to the story, someone stole a formula for the
electrolyte and the formula was missing some key ingredient ( most
likely a depolarizer ). The caps made this way would out gas and
rupture. 
5:35 a.m.
Because the caps blow out the bottom. Most caps have a rubber seal at the
bottom, and the aluminum can is crimped around it. The caps (in my
experience) rarely split from this problem. Instead, they swell until they
force electrolyte out from the crimp area. I'm not convinced that anything
you can do will prevent damage. Better just to replace suspect caps.
--John
-----Original Message-----
From: cctalk-admin(a)classiccmp.org
[mailto:cctalk-admin@classiccmp.org]On
Behalf Of Tothwolf
Sent: Monday, February 10, 2003 14:22
To: cctalk(a)classiccmp.org
Subject: Re: Electrolytic cap "protection"
On Mon, 10 Feb 2003, Dwight K. Elvey wrote:
there isn't a
> Awhile ago there was a thread about
electrolytic
capacitors popping
> and then destroying the motherboard they are
on. One of
the ideas was
> to replace them before they go.
>
> Now I was wondering about another idea... Would it be
okay to encase
> the capacitor in silicone gel? Then when
the capacitor pops, it
> wouldn't spread its electrolyte all over the motherboard.
>
> But would this cause other problems with heat or
something? Would it
further
shorten the life of the capacitor?
There isn't much you could cover it with that would stop a cap from
blowing. The pressures can get to several thousand PSI if relief someplace. Wrapping several layers of
paper towel around them
might be better. This would at least keep the mess from the PCB.
There was an article about some bad capacitors made in the last few
years. According to the story, someone stole a formula for the
electrolyte and the formula was missing some key ingredient ( most
likely a depolarizer ). The caps made this way would out gas and
rupture.
Why not just cover the cap with heat-shrink tubing? I've seen
this done
quite a bit in high end switching power supplies. They often
have about
3/8-1/2" extra sticking up from the top of the cap.
-Toth 
6:25 a.m.
Actually the recent caps that have been failing have both leaked from
the botton seal and have had pressure build up to the point of splitting
the upper case top along the little cross hair crimp. So electrolyte has
been leaking from the top and bottom of each cap.
James
J.C.Wren wrote:
Because the caps blow out the bottom. Most caps have
a rubber seal at the
bottom, and the aluminum can is crimped around it. The caps (in my
experience) rarely split from this problem. Instead, they swell until they
force electrolyte out from the crimp area. I'm not convinced that anything
you can do will prevent damage. Better just to replace suspect caps.
--John
7940
days inactive
7940
days old
3 comments
4 participants
participants (4)
-
dwightk.elvey＠amd.com -
jcwren＠jcwren.com -
jrice54＠charter.net -
tothwolf＠concentric.net