Electrolytic cap "protection"

From: J.C.Wren <jcwren_at_jcwren.com>
Date: Mon Feb 10 13:35:01 2003

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_at_classiccmp.org
> [mailto:cctalk-admin_at_classiccmp.org]On
> Behalf Of Tothwolf
> Sent: Monday, February 10, 2003 14:22
> To: cctalk_at_classiccmp.org
> Subject: Re: Electrolytic cap "protection"
>
>
> On Mon, 10 Feb 2003, Dwight K. Elvey wrote:
>
> > > 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.
>
> 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
Received on Mon Feb 10 2003 - 13:35:01 GMT