The lamp is grounded (earthed) is it not?
You almost certainly have a laptop PSU utilising a 2 pin mains cord. You need to change the laptop PSU to a version with 3 pin mains cord, this can be free if you telephone the laptop maker's service line. Otherwise check ebay but it would be advisable to only buy a genuine OEM laptop PSU.
Several makes have had this problem, Sony, Acer, Dell, HP etc; it is stupid penny pinching.
Ok I think I know what this is.
Many laptops have a two wire mains supply at some level and the mains filtering is applied between live and neutral and the (unearthed) chassis.
That puts the chassis at a very high impedance 115vAC more or less.
if your body is between that and earth you will get a tingle.
It proved enough to blow a serial port on one crap laptop I had dealings with, as well.
2 pin figure of 8.
Yes
OK.
OK. Mine is a Medion. In fact I recently had to do a repair on the low voltage side of the charger. The plug that goes into the laptop is right-angled and there is then about 3" of cable between the plug and one of those barrel shaped devices around the cable (not sure what that does...). The laptop stopped charging and I discovered that the cable had broken internally between the cable and the 'barrel'. It was a co-axial cable and I had to cut through it at the break and then solder the core together, wrap insulation around it - then unwrap a length of the outer conductor and solder that together, before wrapping even more insulating tape around the entire repair. I enclused a couple of matchsticks within the insulation to try and stop the repair from flexing. I don't know if this repair might have increased the likelihood of this problem occurring.
OK. I take it though that there is nothing dangerous about this?
Since you have effected a repair you might want to monitor Ebay for a replacement charger, =A35-13 seems to be the range with a genuine item somewhere in that and probably a 3 pin cloverleaf type too. The lump is to prevent RF going out of the laptop and using the lead as a transmission line. They are an annoyance.
OK. Thanks for the tips.
OK, that suggests it not a fault downstream of the lamp switching... point.
ok, since you have a multimeter, set it on a low ohms range and test for continuity between the metal of the lamp and the earth pin of the plug.
Then connect the extension lead and test between lamp and earth pin of the leads plug. In both cases you should see less than 1 ohm of resistance.
Use a high ohms range and measure between live and earth and neutral and earth. You should see either open circuit or a very high reading (>2 MOhms)
Assuming that is all good, then the next check would be to unscrew the socket faceplate and have a peek behind - make sure the earth is connected to it.
If that is ok then things get a bit more tricky since you will need to be comfortable opening and CU (with the power off!).
You need to test earth continuity from the socket to the CU. There are several ways of doing this. First step would be to disconnect the earth, live and neutral wires for that circuit. If its a radial then the will be one of each, for a ring two of each. You can identify the right set by which MCB they connect to.
Now in the case of a ring, do a low ohms continuity check between the pair of earths, the pair of lives and the pair of neutrals. You should expect a low reading for each (under an ohm probably), with a slightly higher reading on the earth (but only a fraction of an ohm) because the wire is thinner.
Now at the CU, twist the live, neutral, and earth together on one end of the ring (or the only end of the radial). Go back to the socket and measure low ohms between L & E, N & E, and L & N. Again you should get three low readings, with the L & N test fractionally less than the other two.
If you get through that lot without finding a fault, then post back for more!
Sounds like TN-C-S (aka PME - may even have a yellow PME sticker on it). That should provide a very effective earth - hence there is no circumstance where this sensation is "normal".
Ah, should have read this one before posting the last set of fault finding tips... ho hum..
Sounds like the mains input filter on the laptop charger is leaving its output loosly connected to about half mains due to the lack of an earth connection. If there is any part of the conductive chassis of the laptop that is touching you, then that is where you will be picking up the voltage, and in turn feeling it when you touch something earthed. Its maybe even possible that just being in close proximity to the laptop (i.e. on your lap) will be enough to capacitively couple you to the voltage even if you are not directly contacted via metal parts.
Its not generally a safety hazard however.
The problem either isnt really a problem, or is an unearthed lamp, as has been said. We cant tell you which, testing it with a megger is the way to find out. That's part of a proper PAT test, in case such is readily available to you. Its your choice if you earth it or dont.
FWIW I dont like unearthed free standing metal lamps, too high a risk of a live case.
NT
Yeah, at the time I posted I was wondering if the lamp used 12V halogens, with an external transformer and was possibly in a socket with faulty earth.
As soon as the laptop was mentioned that became obvious that it wasn't really an earthing /problem/. My own laptop will do the same if you sit it on your lap while wearing shorts, or if it's standing on top of an earthed data cabinet, and you touch both the cabinet and laptop while it's charging.
You should get a short circuit (0 ohms) earth pin to case. If it isn't
0 on the 200 ohm scale there is one problem.Another check with the meter is to measure the voltage between the case and a central heating or other water pipe (ensure the connection is on the copper pipe and not through paint). Set the meter to 250V ac, or higher to start with. If it reads at all the internal insulation within the lamp is breaking down.
Unlikely to be a general mains problem but one has to consider all eventualities.
Thanks for that John - and apologies for having put you to the trouble of typing out your comprehensive trouble-shooting tips higher up the thread. It was only once I had started on some trouble-shooting that the actual problem became apparent!
Tis ok, might be useful to someone at some point ;-) (anyway - I should have read more of the responses before replying!)
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