Trembling laptop

It is an interesting point about the correctness or otherwise of any reply to a post or indeed the competence, experience or otherwise of the responder.

There is no way anyone reading a forum can know and determine the competence of anyone posting a reply - the medium is simply not set up to do that. All anybody reading a thread can do is take at face value and evaluate for themselves the replies.

I am pleased that the OP went and got advice face to face as this allows at least a little more confidence in the replies.

Perhaps a prominent 'health warning' ought to appear on the site saying that all and every opinion expressed are solely those of the individual posters and no liability can be etc etc' sort of thing.

I am sorry that I may have lumped everyone who is competent together with those who just guess or work from a single example, but online there is no way to tell people apart - a reader must always make their own decision.

Edited By Nick Clarke 3 on 15/07/2020 14:28:59

Correct, but I did require a KNOWN erthed object, the screw was just an example. I'm sure someone would have complaind if I'd said to stick it in the earth hole of he socket , and that is not rellable unless you have a correct sized pin in it.

Robert G8RPI.

Hmm .... I interpreted that to mean a vibration or acoustic trembling. Everyone else seems to have understood electrical fault.

It's one of those things you have to have felt to understand. With very low currents at mains frequency light contact wit a live part e.g. with the bak of your hand, produces a feeling more lie a vibration thna a shock. Often firm contact produes no shock or other sensation. It seems to be dome kind of physiological effect with the skin and maybe short hairs. A bit weird but well established.

Robert G8RPI.

Bandersnatch,

You are not alone, I too thought it meanst some sort of vibration.

Robert,

News to me, but then what do I know!

I have experienced slight mains leakages which have felt like what they were - electricity, and which showed up on the mains testing screwdriver. No comments please about that one. I wonder if in fact it is very individualistic, ie only certain people can feel it.

Regards,

Peter G. Shaw

The OP refers to trembling. I also thought mechanical. Perhaps the OP could confirm.

Roy

I’m going to say something which will, I know, raise the ire of certain of our contributors, but first I wish to relate a personal anecdote. It does have a bearing on things, but initially it may not seem so.

50 or more years ago I casually mentioned at work that I was doing something either at home or at the church I attended in those days, and promptly got verbally jumped on by one of my colleagues. He claimed that I was taking work from someone else, and how would I like it if someone off the street came in and started doing my job? A silly argument because for anyone else to do my job presupposes that the “comer-in” knew what he/she was doing, that he/she had spent some considerable time being trained.

Interestingly, work in the home for that particular job, although reserved at that time to the company, may now be done by anyone, but that is unimportant at the present time.

Fairly obviously, my colleague was a union man through & through, and we all know about the stranglehold the unions had over industry back then, ie, pick up the nut you’ve just dropped, and cause an all-out strike!

So, back to today. I wonder how much of the present restrictions on home electrics has been caused by electrician unions persuading polititians, who are not necessarily the best technical people in the world, that electricity is too dangerous to be left to people who do not have the requisite pieces of paper to show that they have attended some sort of course. I’m sure we all know the stories of the house holder, someone with a degree in high voltage electrical planning, but did not have the requisite piece of paper, so wasn’t allowed to rewire his own house, or the polititian who got himself shocked by a faulty washing machine, etc., whilst there is a story of a qualified electrician who could not find the fault, and had to rely on the householder to do the faultfinding. Ok, maybe exaggerated perhaps, but like a lot of things, perhaps with a grain of truth therein.

It does seem to me that more and more we are being told to leave it to the experts, when in reality, anyone with even just a smidgeon of common sense could do the job easily and more cheaply.

Regards,

Peter G. Shaw

Edited to remove a superfluous postscript.

Edited By Peter G. Shaw on 16/07/2020 11:48:35

Trembling is a better description of the sensation than tingling. It's extremely slight and is eliminated if more pressure is applied. It's definitely a mains frequency. I'm told that not everybody can feel it, but my wife is also able to detect it. The screen has a metal bezel but the the trembling is not apparent on it; it's only apparent on the metal cover around the keyboard/touchpad.

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I feel a similar ‘tremble’ from the iPad sometimes [and I believe that’s because the level is liminal] ... regardless of whether it is plugged-in or not.

Source is most likely to be the onboard oscillator that drives the display, Methinks

MichaelG.

Not to belabour the point but "mains frequency" does not, ipso-facto, mean it's an electrical as opposed to mechanical sensation .... just that it (presumably) derives from an electrical source.

Feed a low-level 50Hz into a loudspeaker and put your fingertips on the cone and you'll feel a "mains frequency trembling". Many other mains frequency operated (thought not necessarily mains voltage) mechanical devices emit low-level mechanical vibrations at that frequency. (Probably hard to avoid if you specify a low enough detection point).

Check with an oscilloscope?

The "vibration" is definatly caused by low currents flowin through the skin under light contact. This can be proven by diverting the current i.e. get someone else to make good contac wih an other conductive part of the item. I only happensat very low currents.
You can also get the senstation by lightly touching something grounded but not connected ot the mains when also in firmer contact with an AC source. Again the source may nt be obvious.
The best check is still with an AC millameter to ground.

I have frequenly seen issues with visitors to the UK from north America using laptops (class 1 grounded ones) on travel adaptors that have no ground connection. The power supplies have two capacitors to ground, one from live and the other from neutral. These form a 50:50 votage divider to the ground connection so if you measure thee voltage on eposed metal like the USB port you see about 110V AC. The current is very low because the capacitors are the sme value. If one capacitor fails open circuit the item will still work but if you remove the earth there will be over 200V at much higher current available.

The sis similar issue with VFD EMI filters including those built in. These are large enough that significat current can flow if the earth is disconnected. You should never rely on the mouning screws for earthing, always connect an earth wire. Larger drives will trip a domestic 30mA RCD even when operating normally.

On qualifications, I'm not an electrican but am a professional eletronics engineer (Chartered Engineer)and apart form my current work on aircraft systems I have ben responsible for safety and EMI/EMC approval for equipment the used servo drives that are electrically the same as VFDs. I was lso taught and carried out elecriacl installation work many years ago.

Robert G8RPI.

" I wonder how much of the present restrictions on home electrics has been caused by electrician unions "

Peter, the Gas fitters got legislation through (and rightly so) so the sparkies had to have their pound of flesh. Having said that, an electrical fault could blow the incoming supply fuse, a gas fault could take the block out.

Pre "Corgi" a "Builder" fitted a bathroom into my rented house. He "forgot" to connect the bath overflow and when called back to explain wet patch on ceiling below, his retort was "Shouldn't have had bath so full". Next door neighbour said I'd done nothing but moan about the fitting (two weeks estimate two months actual) and the poor quality of workmanship. At the end of the day, not my property and not my money, so fine. Despite seeing the performance and c**p job, NDN had them fit a gas hall heater. I kept smelling gas and asked if ndn could. About a month later, the gas board had fitters converting everyone to North Sea Gas replacing Jets etc in all gas fittings. Despite the "New" Installation of their heater, Feed pipe from gas meter to fire had three leaks, gas fitter surprised they couldn't smell it.

Late father in law asked me to check an electric fire he'd added a couple of extension wires to. On a previous posting I said that wiring a 13A had six combinations, now multiply that by three. Told him NEVER to have a bash" again.

Regards Ian.

Ian,

I agree when it comes to gas - it's something I do not know about, or perhaps I should say that I do know enough about it to severely leave it alone.

Perhaps unfortunately, having had 35 years in the telecoms industry, I do have electrical knowledge, ok, maybe not to Regs 18 or whatever, but having seen what some of these so-called electricians do, I would much rather trust myself than them.

It's very unfortunate that my experience of the average so-called British workman is such that I now have a deep mistrust of them and as a result have ended up doing all my own technical work for many a year, that is everything from car maintenance to rewiring my own houses to repairing tv's, radios and other household appliances. Unfortunately, I am now of an age where it is becoming difficult to do it myself, so I am forced into a situation whereby I have to trust people. Maybe I've been lucky but where I now live, a rural location, I have managed to find reliable people, something that would have been difficult at my previous location.

A quote from my garage mechanic: "Living in a village means that I have to do a good job otherwise word quickly gets round and I go out of business." I think that may be why I find the quality of the workforce here so much higher.

Peter G. Shaw

MANY years ago the then london Electricity Board changed our meter. My wife started complaining that the plug "flashed" when she pulled it out of the socket. When checked, the polarities were reversed. the next LEB man came and went berserk wanting to bring all his superiors to see. "Not pygmalion likely, just swop the cables to where they should be" was my response.

I have lost count of the cars that where the garage mechanic has been incapable of adjusting things to to the manufacturer's settings. One tractor dealership shop manager actually boasted to me that on the first service they never retightened the head bolts on our engines! The manufacturer's Service manager was less than impressed by that!

Amazing how making the right settings can produce such an improvement in performance!

With the advent of yield tightening and electronic controls such incidents are , thankfully, less frequent.

"Fine tuning" was what it used to be called.

Howard