small valves and RE: OT

[Allison]

>
>Subject: Re: small valves and RE: OT
>   From: ard at p850ug1.demon.co.uk (Tony Duell)
>   Date: Wed, 27 Apr 2005 00:49:28 +0100 (BST)
>     To: cctalk at classiccmp.org
>
>However, there are plenty of other people reading this list, who might 
>come across similar sets. I would hope they might now realise that the 
>chassis could be live.

Ah, threin lies the reason.  However good point.  

People here play with power in the form of higher voltages, also in 
the form of high energy.  Some of those computer supplies designed 
to pump out dozens to sometimes  hundres of amps of power posess 
the capability to melt off a ring (and the encircled finger), watch
or cause a splatter of melted metal in the eye.  Trust me, I have 
been been to 1500volts and back due to fools around me and their
pointing fingers. I've also seen what an 80amp regulated power 
supply can do to a 1/4" shank screw driver.  That little ditty 
vaporized in a nice UV rich arc.  Had me seeing spots for a 
week(welders burn). Oh and the guy fixing it was quick state he 
had unplugged it. So yes, a reminder for those listening is far
from out of order.

>[1] The presence of a mains transformer in a valve radio does not imply an
>isolated chassis!. It was not unhead-of for the transformer to be to
>supply the heaters only, with the HT coming by half-wave rectifying the 
>mains, thus giving a live chassis. Some UK sets even had the heaters in 
>series, runn from the mains via an autotransformer... 

Yep, that too!  

I might add that something "grounded" can be more unsafe until your 
sure there is NO POTENTIAL differences.  I got dinged in NYC one 
fine day due to a mere 65vac differential in grounds between the
12th and 14th floor.  And they couldn't understand why the RS232 
drivers were being fried all over the place.  Seems equipment 
ground wasn't.

Electrons are our friends, they have a dark side too.  Always play 
nice and use proper technique.  Failure to do so really can take 
the fun out of it.


Allison