[sdiy] KN-75 optocoupler

[Colin Hinz]

On Fri, 21 Dec 2007, Gene Stopp wrote:

> Back in my early tech days we used to blow up LEDs for the heck
> of it at work. We had a 5-volt gazillion-amp power supply that
> had voltmeter cables on it for destroying hard-to-find short
> circuits on newly assembled circuit boards (we called it the
> "f*ck-you" power supply). The LEDs would pop like a .22 going
> off and the pieces would go "tink" all over the lab - eye
> protection needed. We did other silly things too like pour
> solder from the solder pot into vaious molds like coffee cups
> and burn things up with heat guns but that's another story.

Yeah, I've cleared PCB shorts using a monster-current low-voltage
supply. I've also learned that you can nicely pop the lids off
a bunch of ceramic-DIP ICs using a beefy 24V supply. Naturally,
the IC die no longer looks much like it used to....

An 1000 uF electrolytic capacitor with improper voltage applied
becomes the proverbial "lab rocket" (complete with rocket exhaust)
which is much kinder than what a tantalum capacitor does when
subjected to similar mistreatment.

Apple Computer Corp. saved a few pennies by using unshrouded headers
on the floppy disk controller boards for the Apple II. The drives
used a single ribbon cable for both signals and power, and plugging
in the cables incorrectly (the common "off by one row" problem)
would result in +12V going to the +5V logic ICs. The curl of
smoke wafting out of the floppy drive door is pretty tragic to see.
(This happened to a classmate and very good friend, not me. I was
the guy who was trying desperately hard not to laugh.)

I wish I could write something on-topic, but alas I haven't been
doing anything synth-ish lately. I recently stumbled across a heaped
mound of chord organ electronics, and it was all useless mangled
trash except for the reverb tank, which was pristine and unscathed!
One of these days I'll actually interface it to something....

- Colin Hinz
   Toronto, Canada