>Let this be a warning to designers - don't rely on an external plug-in
>regulated supply alone to protect your hardware. Especially when using
>a standard plug & jack pair as would be found on any unregulated wall
>wart. Had this scanner had a voltage regulator on the main board, or a
>different type of power plug to the regulated supply, it would not have
>mattered if the wrong wall-wart was plugged into it. The regulator might
>have gotten hot and gone into thermal shut-down, or maybe popped a fuse.

I have seen worse than you describe. A company I worked for had a laptop and
one of those LCD displays you put on an overhead projector, both made by
Sharp. The two items had almost identical looking mains supplies with
identical connectors for the DC out, but one was reverse polarity to the
other. One day the inevitable happened while setting up a sales demo for a
very important client - result two very dead and expensive items.

If the laptop and display had been from different manufacturers you could
wear the different polarities out of the supplies, but when they came from
the same manufacturer ...

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