6 Sep
2014
6 Sep
'14
12:37 p.m.
Chuck & All,
On Fri, Sep 5, 2014 at 4:23 PM, Chuck Guzis <cclist at sydex.com> wrote:
I think you should stop working on the Altair and sort out your workshop
wiring. Before you plug soemthing in with a serious leak and get
electrocuted.
Regardless, it doesn't answer the question about why the chassis isn't
grounded. The 8800 was most certainly equipped with a 3-conductor line
cord.
You'll have to look up a bit for the answer.
The chassis most certainly +does+ have a 3-wire cord, and it's properly
connected. Thing is, I live in a really old house (for the USA, anyway) and
it turns out that one of the circuits that's near my workbench doesn't
actually have a ground wire - and it turns out that's the circuit which was
being used to power the Variac which in turn powers the Altair.
I only discovered this issue last week, in the process of working on the
Altair, when I felt that tell-tale buzz on my fingertips as they happened
to lightly graze the chassis at one point. Same feel you get from a vintage
amp with a 2-wire cord and an AC line bypass to chassis.. the so-called
"Death Cap", in the lingo of some guitar doofuses who don't seem to grasp
the concept of impedances, and how little current that 50-100nF cap can
actually pass through the resistance of a human body at 60hz.
Well, 100nF on a 110V 60Hz supplywill pass over 4mA. That could be enough
to be dangerous under certain condtions. You certainly would not get me
to tocuh an unearthed chasssis connected to the live side of the mains
through a 100nF capacitor.
-tony