"Boris Mohar" wrote in message
...
On Tue, 21 Jul 2009 19:40:49 +0100, "Arfa Daily"
wrote:


"Nicholas Bodley" wrote in message
news
On Thu, 16 Jul 2009 17:38:16 +0100, Arfa Daily wrote:

I don't think I have ever had a domestic incandescent light bulb [...]

This commentary reminded me of a quite-unpleasant experience in late
boyhood. Apparently, an incandescent bulb in the cellar had a film of
moisture on it (it had just been turned on). When I touched the glass, I
got a nasty shock; damp concrete floor, etc. The socket must have been
wired with its threaded shell to the hot side of the line.

Not the bulb's fault, of course.

Btw, hot glass is conductive, just about certain.

Regards,
--
Nicabod =+= Waltham, Mass.

Well, if it is, and I rather suspect it's not, the amount of conductivity
is
very small. I work a lot with power valves (tubes) which run hot enough to
take your fingerprints off in decimals of a second, and these often have
as
much as 800 volts on the anode pins. Some years back, I used to work with
high power audio distribution amplifiers on a community radio network. The
(foot high internally assembled with nuts and bolts) tubes on these 7 foot
tall amplifier cabinets, often used to run so hot that the glass was
actually glowing dull red. I have seen dents in the glass where the vacuum
has started sucking on areas that have got *so* hot that they have
softened.
The HT supply on these beasts was about 2.5Kv as I recall, derived from
mercury vapour rectifier tubes.

Given these facts, if the glass had much conductivity when hot, you would
pretty soon be into having leakage paths between the pins, and to the
grounded retainer metalwork, that holds the devices into their sockets,
wouldn't you ?

Arfa

Any links to these giants?
--
Boris

Friend of mine still has a couple I believe. I'll get him to check the
numbers on them (it's been a long while ago, and I can't remember any more).
I'll also see if I can get a coupla piccies of them. The amps in question
fed a radio relay network around large areas of the town. They were located
in the cellar of a house in the centre of town. Above them on the ground
floor, was our workshop, which was always lovely and warm in the winter :-)

On the first floor, above that, was the control room. The radio receivers
were located there, and a large patchboard, where the distribution lines
were routed, using the big old three pin Bulgin plugs and sockets. There was
also a desk console, with an array of meters, which measured 'load'. They
were actually measuring audio current going out on the lines.

We used to have fun on a slow Saturday afternoon, when there was no no
bosses about, by waiting for an important set of sports results, and then
either pulling the plug on a whole area, or switching in the spare receiver,
which we had pre-tuned to an offshore pirate radio station. Then wait for
the phone to start ringing off the hook down in the office, where some poor
part time lady would be located to take any service calls ... :-))

Arfa