Electrical hacking (was Re: [Techtalk] [OT] charging USB device without a PC)

Maria Blackmore mariab at cats.meow.at
Sun Apr 13 14:21:20 EST 2003

On Sun, 13 Apr 2003, Telsa Gwynne wrote:

> I think the only thing I ever dared touch was a printer which Alan was
> convinced was dead. It was junk anyway as a result, so I took it apart
> and cleaned it.

Cool :)

> And good gods, it started working.

You do realise this might be as much because you took it apart and put it
back together again, but too many people use things to death without ever
cleaning them.  I once came across a printer as a field engineer that had
been used dozens of times a day, every day, for 2 years.  I tried to clean
it, but the ink had actually started to corrode the metal of the chassis,
and there was a stalagmite 2-3 inches tall in the bit where the head is

> I was proud. Of course, the advantage of a printer is that there's no
> things storing up some massive charge inside them.

hmm, I've got these two little brown spots on one of my fingers that would
suggest otherwise :)

Remember that things with a power supply always have capacitors in the
power supply in order to smooth the voltage.  Often these capacitors hold
quite chunky amounts of voltage, more than enough to overcome the
resistance of your skin and do what capacitors do best through you :)

Fortunately, this is rarely harmful, unless you get one arm connected to
each side of the capacitor, it's usually voltage flowing across your chest
in any direction that will kill.  Anything else just hurts

> In the case of my printer, I did it because it was that or tidying
> up (or something :)). And the time was worth less than the confidence 
> boost of discovering that I had just fixed something.

Cool :)

This is what I was talking about in my previous post :)

> It went down with "first card I put into my computer", "first computer
> I built from bits", "first install I did on my own" and, um, "first
> time I cleaned a mouse" (don't laugh: we have to start somewhere, and
> I didn't grow up knowing about these things).

See my previous post about not letting not knowing something to stop you
from doing it :)

> Yeah, knowing when to say "perhaps I won't do that, then" helps!

And knowing when to ask someone else about the possible risks.
People who haven't have given us some stunning darwin awards though ;)


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