-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Alan B. Pearce
Sent: Thursday, June 26, 2008 11:51 AM
To: Microcontroller discussion list - Public.
Subject: Re: [OT] Apologies to Olin


>I remember a colleague who should really have known a lot better, hooking 
>the ground terminal on the front panel of an oscilloscope to the ground of
>a computer he was looking to do some serving on, using about 3' of hook-up 
>wire, removing the ground lead from the scope probe because it was in the 
>way, and then wondering why he could not see any signals that he knew were 
>there, clocking at 20MHz. The big open loop just put so much 50Hz hum on
>the screen that the signal he was looking for was totally swamped.
>Unfortunately this is the sort of thing that does catch beginners out -
>after all a piece of wire is just that, forgetting that it becomes a turn
>on a transformer of a magnetic field that envelopes the environment that is
>full of 50Hz interference.


I did that with an early color "Computer", and BLEW out EVERYTHING.
It had a HOT chassis!  If you don't know what a hot chassis is,...
Be glad you live in an age where that is no longer allowed for sale.

Tom

  *
  |  __O    Thomas C. Sefranek  WA1RHP@ARRL.NET
  |_-\<,_   Amateur Radio Operator: WA1RHP
  (*)/ (*)  Bicycle mobile on 145.41MHz PL74.4
 
ARRL Instructor, Technical Specialist, VE Contact.
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