clover leaf computer leads insulation fault.

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My son was asked on the way home from work to pop into a school and find out why a trolley with 20 lap tops was tripping a RCD but the results have got us scratching our heads. Half the clover leaf moulded leads were showing low insulation readings on all cores varying from between 0.1MΩ and 0.25MΩ he did not have the time to cut open the leads but we can’t work out how leads could deteriorate like this? I have read the report about a recall with substandard cable but the description does not seem to explain the high number of leads all failing within a few months since my son was called to same trolley and found a filter faulty.

I asked about any signs of liquid and he assures me the trolley was clean.

Has anyone else had problems with clover leaf computer leads?
 
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Do you know whether these leads have in-built filters?



Regards
 
Do you know whether these leads have in-built filters?
That's a very obvious question, although I've never heard of any such leads which do have filters. When I saw eric's post last night, I did some googling, but could find no mention of any such leads with filters - although that obviously doesn't prove that they don't exist.

Eric's post seems to imply that L-N, L-E and N-E IRs were all similarly low in many of the leads. That seems very odd, even with mechanical damage - and my first reaction (like eric's) would probably be to wonder whether the connectors/plugs at one end or the other were 'full of water'. Although nothing is impossible, to get multiple pairs of insulated conductors showing IRs in the range 0.1 - 0.25 MΩ (rather than very much lower than that) as a result of mechanical damage would seem exceedingly improbable.

Kind Regards, John
 
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I was scratching my head the only thing I could think of was flux on soldered joints being wrong type and slowly etching its way through the cables.

My son tells me no sign of liquid or cable damage and just can't think of anything in a simple cable which could cause the fault. My son wants an old cable to cut open as he also can't think of anything in a cable which could cause the fault.
 
I was scratching my head the only thing I could think of was flux on soldered joints being wrong type and slowly etching its way through the cables. ... My son tells me no sign of liquid or cable damage and just can't think of anything in a simple cable which could cause the fault. My son wants an old cable to cut open as he also can't think of anything in a cable which could cause the fault.
Yes, it really is extraordinarily odd. It only takes a micron or two of intact PVC to give a very high IR, and the moment the PVC ceases to be 'intact', one is more likely to get an IR close to zero than 0.1 MΩ or above. Maybe there is something very odd about the material of the insulation, and something very strange has happened to it? I have to say that my 'first reaction' would still be to suspect ingress of liquid (which could explain the findings), but your son seems to be pretty sure that such is not the case.

Do you know if the leads are of a 'reputable' make/source, or are they simply 'anonymous'?!

Kind Regards, John
 
I import a lot of Chinese stuff direct and a couple of times Ive had a PAT tester come back to me saying the cable is faulty. Once we had a fire on a workboat caused by an overheated cloverleaf cable. luckily no disaster, just a nasty smell!

I suspect that the PVC might be "filled" with something less insulating... Ive hacked a few leads to pieces and the quality is atrocious, variation in wall thicknesses, very little conductor, cracked insulation etc etc.

you can usually tell the quality outwardly, because the finish is poor, sometimes the plugtop is too small (think that might contravene regs), the joins to the pins inside the plugtop are bad, the armour makes the cable overly rigid....

once I got a load of cctv cameras & peripherals that stank of wee. god knows what that was all about. Luckily they were going into cowsheds.

the gear is so cheap I don't worry about it, just replace the cables with good ones from CPC.

I believe the Chinese have even come up with their own CE scheme, bless them, which has a very similar mark to the European CE mark. not that [/i]that means anything.

get a sample of the "PVC" from the leads, heat it up a bit and then megger it?
 
I believe the Chinese have even come up with their own CE scheme, bless them, which has a very similar mark to the European CE mark. not that [/i]that means anything.

That's a myth. They just copy the CE mark, as well as any other approval marks they think relevant.
 
Seems odd. The only laptop trolleys I have seen (and only as a user) just had the extra-low-voltage lead coming out of a grommeted hole long enough to go to the laptops power socket when it was in its slot, and I think a fan at the bottom drawing in cool air to push out of vents at the top.

Rightly or wrongly I assumed in the bottom of the trolley there was a pair of 16 way mains adapters and mess of laptop chargers trying not to overheat.

At which point none of the leads are exposed to mechanical damage. Maybe the whole lots just got really hot and soft, but I doubt its got the hot without noticable external re-shaping.

Sounds like time to replace the leads....


Daniel
 
Rightly or wrongly I assumed in the bottom of the trolley there was a pair of 16 way mains adapters and mess of laptop chargers trying not to overheat.

At which point none of the leads are exposed to mechanical damage. Maybe the whole lots just got really hot and soft, but I doubt its got the hot without noticable external re-shaping.


Daniel

If the materials are substandard the insulation could easily be compromised by temperatures as low as 50C. You'll find the average loaded laptop power supply will easily exceed this in a confined space.

I would make the fair assumption that all the leads are of substandard quality and replace them, and take care to ensure they do not rest on hot surfaces.
 
Thank you for the reply. The faulty leads will of course be replaced but there must be loads of these trolleys and the worry is more to do with the rest.

When I asked for a equipment register I was met with a blank expression. Other than the schools I have PAT tested it would seem there is no record as to what is in the school and clearly items like this are locked up so ensuring non miss inspection is hard.

Hence the question if others had also found the fault it may give pointers as to how common and how much time needs to be spent ensuring the leads are changed.

There was a filter on this trolley which went faulty around a month ago so we are sure there was no fault on leads a month ago which is rather worrying specially as being IT equipment which is unlikely to be damaged they have been given a 4 year PAT test. After this I would question giving them 6 months!
 
Thank you for the reply. The faulty leads will of course be replaced but there must be loads of these trolleys and the worry is more to do with the rest.

Which is why I said all the leads. Bulk prices of ~£2 aren't too hard to come across for proper leads.
 
There are several types of PVC that are intentionally conductive used mainly for anti-static applications.

I can think of situations where a signal cable with such conductivity between cores would be of benefit in discharging static charges before the cores were connected to a sensitive piece of equipment.

But not for mains leads.

As others have said the "quality" control in some Chinese factories ( aka kitchen table out workers ) does require come improvement.
 
This thread on the IEE forum might be of interest ... http://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=56355[/QUOTE]
As you say, that's interesting. It raises the possibility, which I hadn't even considered, that it could be the material of the moulded cloverleaf plug that is partially conductive, rather than a deterioration of insulation of the cable cores.

eric: Did your son by any chance test IR between cores and the material of the moulding of the connector?

Kind Regards, John
 

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