My electrical theory is fair but not great. Can someone please
I have an old Anglepoise lamp with painted metal arms and painted
metal lampshade (Anglepoise model 90). It has a two-core mains
lead. I am in the UK so this is all at 230-240 volts.
Today I touched the outside of the lampshade and got a sort of vey
mild tingle feeling which felt "odd". When I used a mains tester
screwdriver on the exposed metal (at the joint of the lampshade
and support arm) then it glowed as if the metal of the Anglepoise
lamp was live.
I unplugged the lamp and tested the resistence between the live
pin on the mains plug and some exposed metal on the lamp. I got
no resistence reading at all (i.e. it must have been a very high
resistence). I then tested the neutral pin in the same way and
got the same high resistence result.
So the lamp seems ok. But something seems to be wrong!
QUESTION: Is my lamp safe to use and could I get a shock from it
in its present condition?
QUESTION: If my lamp is unsafe then is there a repair I can do?
Thank you for any info.
PS: Picture of Anglepoise model 90:
I would guess that the insulation is failing somewhere. Your test with
the meter wasn't high voltage and didn't show it up. You need proper
equipment to do that test.
I would guess that replacing all the wiring would probably do it. It
*might* be the lamp holder, but I'd change the wiring first. If you do
replace the lampholder, it's probably a special heat resistant one
We have an Art Deco brass lamp which I can feel 'tingling'or 'trembling'
when I touch the base or the stem. The wiring has been checked and renewed
several times and it still happens - and Spouse is absolutely thorough about
doing a good job mainly to prove me wrong because he can't feel it. I can
still feel it.
I could also, once upon a time, feel the same thing from a metal electric
kettle and nobody else could. The kettle was taken away by the first child
to go to university. Over the years we lost all our electric kettles like
that which is why we're left with an ancient copper one on the gas hob, it
used to be used by Spouse's grandmother on their coal fire. But that's a
It's not a shock and it can only be felt with the lightest possible touch -
but it's very definitely there and can only be sensed when the lamp is
plugged in and the outlet switch is on. The lamp itself doesn't have to be
I've never suffered and I doubt that the OT will either. If he were going to
he would have done by now.
On a sunny day (Wed, 27 Apr 2005 21:48:01 +0100) it happened "Mary Fisher"
It is a common case, and possibly capacitive coupling between the hot wire
and the metal frame (if no isolation problem).
The responsible things to do is use a 3 lead mains cable and plug, and connect
the ground to the metal frame.
ANY other configuration will leave the possiblity of a short between a live
wire and the frame, causing the metal to become live.
When ground is connected a short will blow the fuse.
Then it is probably not being plugged into a properly grounded outlet.
At the very least, you should have him install a GFI outlet in the place
that the lamp is used. Better is to make sure that the safety ground on
the outlet really has a good, low impedence run to the main breaker box.
Of course, he may have failed to properly connect the safety ground to the
metal parts of your lamp. :)
please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
Once had lots of problems like this, and when i got a shock off the
earth I did something about it. It turned out lots of the various earth
connections around the house were just copper cable twisted together,
so of course the joints had gone high R over time. Also the earth rod
was disconnected, so there was no E anywhere anyway. Just glad there
was no shower.
Following fitting the earth connection, does it tingle even
when switched off at the wall socket?
If so , it sounds like you are discharging a static charge
into the lamp, rather than getting a charge from it.
Touching something that is earthed (eg wall radiator)
shortly before touching the lamp should prove/disprove this.
But don't touch the two at the same time until you have had
the lamp professionally tested for safety - I wouldn't have
trusted my hublet with anything electrical..
On a sunny day (Wed, 27 Apr 2005 22:20:56 +0100) it happened "Mary Fisher"
Well, I was in this house once, where they also earthed the stuff, but it
then turned out the earth (I had to install some equipment there) was not
connected to anything, it was originally connected to water pipes, but
somebody had just cut the wire.
You (he) can test if earth is there with say a 40 W lightbulb between earth and
live. It should light.
Then test between live and your lamp frame, it should light too.
The only alternative is that you pick up something from the floor (bad wiring
conductive carpet), anything goes.
Its not safe... how good your meter is and how good you are
using are open to question..but the tingle is proof positive
you have some degree of short or current leak in the lamp
wiring to the lamp base metal. Rewire it.
If you get a continuous tingle, then it's _highly_ unlikely to
be a capacitive/inductive/static leak (as others have suggested).
Last time I touched a device and got a minor tingle, repeating
that test while holding on to something grounded was something
I'm not going to repeat. That hurt! Dumb me. At least
we're only 120V...
You say "old", and the picture shows that the wiring in the
lamp is being moved whenever you adjust the lamp. Possibly
abraded and the conductors may now be intermittently contacting
I recommend removing the wiring and inspecting both it and
the lamp socket as others have suggested. The socket may need
cleaning. If you see worn spots in the wiring, replace it.
If you don't see any obvious worn spots, now you really worry
about the fixture.
Measuring resistance won't be particularly reliable, fancy
equipment or not, because if you have a bare spot on the wiring
in the arms, the slightest bit of movement may break/make the
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
I'd strip it down and check it thoroughly, and if you're still not happy,
destroy and dispose of it safely. Better still, pass it on to trading
standards in case it has a design flaw.
I must point out though that it is rare for UK approved double insulated
appliances to fail and present a shock hazard. If you find a design fault
which could have contributed to the case becoming live, be sure to report it
to trading standards so it can be investigated.
Is it a constant tingling feeling or a momentary minor jolt? It's very
common to get static discharges to metal appliances, but there's also an odd
gentle 'vibrating' or 'buzzing' sensation which can sometimes be felt
touching the metalwork of double insulated appliances. These are perfectly
to check the leak resistance of mains circuits you need a special
"megger"meter.This is usually in the range of Mohms, so usually a normal
multimeter shows infinite resistance (sometimes modern digital ones are
capable of measuring this resistance).It's very dangerous to use something
that gives you (even) a slight shock.If you find it's too much money to have
it professionaly repaired (maybe a worn out cable that touches the frame?)
then better trash it, than put your life in danger.
major in electrical engineering, freelance electrician
FH von Iraklion-Kreta, freiberuflicher Elektriker
dimtzort AT otenet DOT gr
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