Scented ICs

[Gene & Debby Stopp]

I built my own power amps a few years back (not really cost effective, but
a great learning experience as you will see).

Since a power amp is really a big power supply modulated by an audio signal
into some inductive loads, I kind of over-did the power supply end by using
huge transformers and big heat-sunk diode bridges into big waste-basket
sized electrolytic capacitors. During the course of building, I had to
power things up once in a while to check things, and I had a big power
resistor that I used to discharge the big caps after power-down so I could
work on things.

Well the capacitors have big screw terminals on them and I held them in
place with a big plate of aluminum, which also served as the ground side of
each cap. One time, as I powered things up and poked around with a
voltmeter and powered things down again, I forgot to discharge the caps. I
was scraping off one of the cap terminals with an X-acto knife to clean it,
and I shorted across the screw terminal and the plate. I was blown over by
something - expanding gas, photon pressure, sheer fright, who knows - it
was like a lightning strike and it sounded like a .38 pistol going off.

The X-acto knife blade was vaporized, and there were molten metal bits
splashed across the aluminum plate. I like JDM's idea of knowing when to
wear goggles!

- Gene

----------
> From: David Halliday (Volt Computer) <a-davidh at microsoft.com>
> To: synth-diy at horus.sara.nl
> Subject: RE: Scented ICs
> Date: Tuesday, August 12, 1997 1:30 PM
> 
> I worked for Tapco about 15 years ago doing final test on their new line
> of power amplifiers.  We had a lot of QC problems plus the design was
> running *right* on the edge of unstability.
> 
> It was a basic given that out of ten amps, one of them would blow up
> spectacularly - most times, the power supply electrolytics would go
> along for the ride...  The amp was since reworked and Tapco was sold to
> JBL
> 
> > -----Original Message-----
> > From:	J.D. McEachin [SMTP:jdm at synthcom.com]
> > Sent:	Tuesday, August 12, 1997 5:52 AM
> > To:	synth-diy at horus.sara.nl
> > Subject:	Re: Scented ICs
> > 
> > On Mon, 11 Aug 1997, R.Fahl wrote:
> > 
> > > So, can anyone tell me why chips stink so terribly when they blow
> > up?
> > > 
> > > Couldn't manufacturers start making opamps and transistors with a
> > variety
> > > of aromas?  Everybody lets the smoke out of an IC once in a while,
> > might as
> > > well smell good.
> > 
> > While they're at it, maybe they could make chips that visibly and
> > audibly
> > fail.  I remember powering up a new pcb once with the power & ground
> > lines
> > to some TI high current output drivers reversed - a loud pop and
> > ceramic 
> > bits flying out of the enclosure ensued.  I found ceramic bits
> > embedded 
> > in the ceiling!  Which reminds me kids, always wear your safety
> > goggles 
> > when testing boards - you never know what's going to happen!
> > 
> > JDM
> >