[OT] Dodgy electrolytic in 3COM hub

From: jpero_at_sympatico.ca <(jpero_at_sympatico.ca)>
Date: Mon Mar 15 15:12:07 2004

> > -----Original Message-----
> > From: cctalk-bounces_at_classiccmp.org
> > [mailto:cctalk-bounces_at_classiccmp.org] On Behalf Of John Honniball
> > Sent: 15 March 2004 21:13
> > To: General_at_neptune.easily.co.uk;
> > Discussion_at_neptune.easily.co.uk:On-Topic and Off-Topic Posts
> > Subject: Re: [OT] Dodgy electrolytic in 3COM hub
> >
> > > http://www.wowrarelook.co.uk/cap.jpg
> >
> > Great domain name!
> :oD
> It had to be done once I discovered it hadn't been taken...it's the place I
> host my ebay pictures for sales :)
> Adrian/Witchy

Beauiful photo of this swelled up electrolytic capacitor. :-) What
is that digital photo camera?

The 7 legged "transistor" is a efficient regulator IC switcher that
down converts input voltage to specific voltage. Good to about 1
amp or so with little heatsinking.

That whistle is the noise of that regulator switcher it works at high
freq. They runs too high freqs to hear but when they get loaded down
or bad caps, they decrease in PWM (more ON time) trying to keep
voltage up (more power transfer, then u can hear the noise. The
swelled up cap is already GONE btw. I have seen all descriptionss of
failed caps. 1. that looks fine and clean but ESR is totally gone,
are *most common*, hence ESR meter is a must. 2, leaking either
end, some types of electrolytes is corrosive & stinky to heavens (1
year old rotten fish) when heated. 3. Swelled up or split top or
uncorked rubber bung. 4. Bad cap that tests good but no good,
that's rare few and diffcult to find. 5. Plain exploded spewed brown
fluff and shreds of spiraled ribbons everywhere.

Dipped blue or yellow disks caps (1KV and up) does vent cloud of pink
smoke. I was amazed when I saw it go.



> Owner & Webmaster, Binary Dinosaurs
> www.binarydinosaurs.co.uk - possibly the UK's biggest online computer museum
> www.snakebiteandblack.co.uk - ex-monthly gothic shenanigans :o(
Received on Mon Mar 15 2004 - 15:12:07 GMT

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