On Dec 18, 11:38*am, "Gareth Magennis"
wrote:
"klem kedidelhopper" wrote in message
...
I've been reading the other thread about Quartz halogen lamps and have
found it very interesting. However since this is a bit off that track
I've started this new thread.
I seems like in the last few years it has become impossible to buy
small Christmas light series strings that have conventional lamps in
them. IE: When a filament goes out they all go out. I've noticed that
"something" happens to these *new lamps that effectively makes them a
dead short when the filament opens. This then maintains the continuity
of the string and keeps the other lamps lit. But of course this comes
with a high price. A higher voltage is placed across each of the
remaining good lamps when this happens.
Little by little as they over cook, and each filament reaches the
premature end of it's life and opens, that lamp is essentially
replaced by another dead short, thereby running the remaining good
filaments at even a higher voltage. Naturally catastrophic failure of
all the rest of the string is inevitable and systematically occurs
unless this "shorting" action fails on a particular lamp and it
actually "opens". Then the remaining lamps are spared.
I know this is what's happening because I've tried to repair several
strings like this. Last night I looked at two identical 50 lamp
strings. One had about six lamps out with one open. There were 35
lamps out on the other, all with with shorts across them except for
one that was "open". The remaining lamps were still good.
My wife seems to think that not having all the lights go out when one
filament opens represents convenience, and trying to explain series
circuit theory to her is an exercise in futility. So anyhow I now have
one string which I've added 8 additional lamps to for a total of 58
2.4 V lamps on it. It runs a bit dimmer but it should last a lot
longer. I also now have a few spare lamps as well.
As much as it ****es me off you have to give the Chinese credit for
figuring out a way to sell more Christmas lights under the guise of
"convenience".
Does anyone know what is actually happening in these lamps to turn an
open filament into a dead short and begin this "runaway" effect? *Lenny
http://people.howstuffworks.com/cult...days/christmas...
That reminds me - when I was about 11, our christmas tree lights failed due
to a faulty bulb socket rather than a bulb. *I thought I'd be dead clever,
and find the faulty socket by, carefully pushing pins through the isulation
either side, and touching them together to bypass the socket, all while
connected to the mains.
The method actually worked, and I found my dead socket without getting
shocked. Hurrah.
So I cut the wires either side of the socket. *Then bared one end, then
bared the other end, and picked up the two ends, one in each hand, to twist
them together.
Only I'd forgotten to unplug the mains.
I got 240v straight through my chest. *I was squatting down at the time, and
my legs spasmed and shot me backwards halfway across the room. *It was about
5 minutes before my heart calmed down enough to be able to breathe properly.
Christmas? *bah, humbug, its dangerous.
Gareth.
As we say here in America you literally got "knocked on your ass".
It's amazing considering some of the stunts we've all probably tried
in the interest of them being a learning experience that we're still
alive.
I remember when I was a teenager grabbing an old tube type TV chassis
off the bench on a hot Summer day. I caught 450VDC from one arm to the
other. I think that the only thing that saved me and my heart was
possibly the skin effect of my soaking wet sweaty Tee shirt. Lenny