The MK Safety plug

[Smiler.]

TheExcession said:

Smiler. said:

Jonesy23 said:

AlexC1981 said:

Anyone know what the hole is for in the top?

'Earth peep hole' as mentioned above? I guess so you could see if the earth core was present as the once wired up the cable might not make it obvious.

My immediate thought would be exhaust of hot air in the event of the fuse blowing. Or heat dissipation when under load. Intersesting point.

Sorry, but not wanting to call you all retards, that little lug on the top, it's there to help you align the top/cover over the plug

Think about it, you've wired the plug and cables, so you turn it upside down in your hand with the back in your palm and the other prickly part in your other hand and then some genius came up with the idea ' what if we put in a notch so that you can quickly align back and front'

Genious!

Why the gap?

[AlexC1981]

I didnt see the comment about the peephole. That makes sense

formula27 said:

OldGermanHeaps said:

As far as electricity is concerned all things being equal, moisture, salinity, distance, area in contact with the source etc then due to ohms law as voltage increases current flow increases in relation so with 240v applied a lot more current flows through you than at 55v, and its the current flow that harms you, voltage doesn't really harm you from a current limited source, you can be zapped with 100000v and just feel a tickle as long as there isn't much current available, but in terms of a supply which has enough grunt to kill you lower voltage = lower current frowing through your bodies fixed resistance = safer.

Correct , well done .

So (always a so with me)

We (UK) dont have the safest system in the world.
As for the plugs
As this thread , a lot of people dont know how to wire them safely and what fuses to use.

Ring mains ,PME ,230 V , plugs that lay pins up , and rewirable fuses.all unecesary, and. Cost related rather than safety.

formula27, I'm no expert but I understand that you are correct that 240V is cheaper because the cabling only needs to be half the diameter of 110V because it only needs half the current for the same amount of energy. The low current used in 240V also means less heat is generated so less energy is wasted as heat.

I don't know how true this is, but I have read somewhere that 110V is just as dangerous because it's enough voltage to make your muscles contract so you can't let go. With 240v you are more likely to get thrown back. At least with UK plugs and sockets you are much less likely to electrocute yourself in the first place. The UK system would seem to be the best compromise between safety, efficiency and cost.

[TheExcession]

Smiler. said:

Why the gap?

Might you be a bit more specific, there are gaps all over the place, which gap are you referring to?

[AlexC1981]

The mysterious hole.

I'm going along with the idea that it is a peep hole so you can see if the appliance has an earth lead. The plug is old enough that there would have been a lot of non-earthed appliances around when it was manufactured.

[anonymous-user]

AlexC1981 said:

I've got an old sleeveless MK plug that's been hanging around in drawers for years and looks like it's had a hard life. It's got the connectors that you wrap the cable round and then screw a clamp down onto it.

Anyone know what the hole is for in the top?

(It's on an ironing board cover by the way, not stained bedsheets )

Thank you
I was going to mention in my original post how the MK Safety Plug "took over" from its predecessor model. I actually remembered that we had some of the older plugs on stuff when I was younger. But I just couldn't actually remember what it looked like. Genuine thanks.

[Perd Hapley]

Top earthin'



This site says:

"The hole at the top above the earth pin was provided for inspection purposes, so that the connection could be seen without opening the plug. Another, probably less accurate explanation is that some older radios had a separate wire for the earth, and this could have been connected via this hole so that is was kept well away from the live pins."

http://www.flameport.com/electric_museum/plugs_13A...

So it sounds like no-one really knows for sure, so I'm accepting nothing less than scans from 1960s MK documentation.

[anonymous-user]

CRT's wonderful things, worst shock I ever had was from one of these, dodgy HV regulator in an oscilloscope that had supposedly been repaired. 36kV and woke up on the floor.

So glad crt's are history and everything is lcd.

[speedyman]

I once put my hand across a dc rectifier because some idiot left the cover off a machine. Burnt fingers and the gritted teeth from the resulting shock I will never forget.

[Who me ?]

techiedave said:

Plugs are not the most interesting subjects and most people won't give them a second thought but I'm referring to this :




By my reckoning 30+ years old now and still a great plug. At one point it was used by Granada TV as their plug of choice admittedly with a Granada Logo on it (I still have 2 of those bad boy variants)as ell as every device in the kitchen having the standard MK safety plug attached to it

It might be pricey now but those secure screw down terminals and flexible cable clip makes it worthwhile
Thank you

A great PLUG for an old PLUG.

[Silent1]

.:ian:. said:

Wacky Racer said:

If you can never remember which colour wire goes where, In the 1980's, I devised this simple rule.

I call it the second letter rule.....

Note:- UK only



sTriped to the Top

bLue to the Left

bRown to the Right.


Saved me from electrocution many times.

Alternatively,
bLue - Live
Brown - the same colour as earth
Green & yellow - neutral as it's two different colours

Served me well and only had a few near fatal incidents

Im surprised no one else has mentioned this but blue is neutral and brown is live, if you swap them the appliance will probably still work but you're switching the neutral meaning the device is always at live potential so if you grab hold of it and the earth has failed whilst switched off you will become the earth and get a shock.

[Jonesy23]

gottans said:

CRT's wonderful things, worst shock I ever had was from one of these, dodgy HV regulator in an oscilloscope that had supposedly been repaired. 36kV and woke up on the floor.

A dodgy scope tried to get me years ago, not really a belt as much an interesting feeling that took a while to go away. Interesting enough that after the first tingle I went back for a second go before I decided it was a bad idea. Very different from a bit of 240Vac or 50Vdc.

Silent1 said:

Im surprised no one else has mentioned this but blue is neutral and brown is live, if you swap them the appliance will probably still work but you're switching the neutral meaning the device is always at live potential so if you grab hold of it and the earth has failed whilst switched off you will become the earth and get a shock.

Swap earth and live and you can end up with a situation where you're wondering why the fan is spinning but the box isn't working, turn it off, realise what's going on and then feel thankful you didn't grab the bare metal case. Important lesson in making sure which pin is which on a custom connector. And fitting an independent safety earth.

[anonymous-user]

Veering slightly off topic but as regards CRT'S
Years ago I lived in a static caravan on a residential site. I can honestly say its ste and I don't recommend it. When it rained it was like people were lobbing peanuts at your roof. The gas bottle worked great on the cooker but was ste at powering the hot water boiler. I must have wasted a dozen bottles with 20% gas left in them before I realised it was still ok for the gas fire.
But I digress -Caravans get VERY COLD in winter
Anyway I had a Philips G8 TV I rented. and what would happen is that if you switched it on the tripler would go "qitik katak zap, bang BANG" as the thing took the shortest route across the surface. Hard to explain but some of you older nay mature gentleman will know what I mean. It didn't matter if the TV was switched on when the room was cold or after it was heated up it would still make no manner of aggressive cracky sounding noises. Actually worse if the room was heated then the telly switched on. I suspect condensation may have had a part to play in this.
Unfortunately sitting there and reading a book whilst the TV acclimatised wasn't an option at the best of times It took me an hour to cycle home and on Mondays Blake's Seven was on so the TV had to go on.
I once decided to clear the area round the tripler and you sort of roll back the rubber coating then squeeze the metal prongs together through the rubber and unhook it from the tube. I once touched the metal prongs - Jeez that hurt like hell remember it to this day. I doubt even if fited with an MK Safety plug it would have been less hurtful

Edited by anonymous-user on Thursday 15th December 03:52

[speedyman]

I worked on Atari video games in the mid 1970's, space invader's, Breakout etc. So I know all about replacing crt's without discharging them. Hair raising stuff Lol

[Halmyre]

A bloke turned up to service one of our Uninterruptible Power Supplies, including capacitor replacement. Opened it up, full of massive capacitors the size of soup tins. He worked very, very carefully!

[speedyman]

A bit more electrical nostalgia. I rewired quite a few houses that had been first wired with lead sheathed cabled. The two internal wires were rubber and cambric covered and the earth was obtained by having wires soldered to the lead sheathing. We made a few bob pulling out the old cables and selling them to the scrap merchant.

[brrapp]

Halmyre said:

A bloke turned up to service one of our Uninterruptible Power Supplies, including capacitor replacement. Opened it up, full of massive capacitors the size of soup tins. He worked very, very carefully!

I was repairing our tumble drier las week , reckoned it was a fault with the motor or the capacitor that starts it so was having a guddle about. I'd unplugged it at the mains but it looked like quite a big capacitor so only half thinking, I stuck my screwdriver across the terminals to see if was still holding a charge.... it was and my screwdriver is no more .

[anonymous-user]

speedyman said:

I worked on Atari video games in the mid 1970's, space invader's, Breakout etc. So I know all about replacing crt's without discharging them. Hair raising stuff Lol

Me too, I cut my teeth on repairing classic arcade games. Many an hour spent on my knees in a busy arcade trying to troubleshoot a faulty AR2.

I took a full hit to the chest from a crt that I was carrying, I still managed to keep hold of it but there was some swearing and my arm went numb for a while afterwards.

[ou sont les biscuits]

Silent1 said:

Im surprised no one else has mentioned this but blue is neutral and brown is live, if you swap them the appliance will probably still work but you're switching the neutral meaning the device is always at live potential so if you grab hold of it and the earth has failed whilst switched off you will become the earth and get a shock.

If you think about it, the appliance must work. On the continent with Schuko plugs, you can put them in either way round. The appliances always work no matter which orientation you use.

[Silent1]

ou sont les biscuits said:

Silent1 said:

Im surprised no one else has mentioned this but blue is neutral and brown is live, if you swap them the appliance will probably still work but you're switching the neutral meaning the device is always at live potential so if you grab hold of it and the earth has failed whilst switched off you will become the earth and get a shock.

If you think about it, the appliance must work. On the continent with Schuko plugs, you can put them in either way round. The appliances always work no matter which orientation you use.

Isn't that also why most European sockets are unswitched? So that you can't isolate the neutral in a device?

[Morningside]

speedyman said:

I started an apprenticeship as an electrician in 1968. I saw quite a few diy electrical bodges. 5amp rewireable fuses for lighting circuits which had been rewired with 30amp fuse wire or just plain copper wire strands. A friend of mine said he saw one where a nail had been used as a fuse. Also a heater wired above a bath tied onto a nail with string are just a couple of the most memorable ones. Always made me wonder why the public hardly ever touched gas, but you can smell it. Hardly ever touched water, but you can see it. But electricity lots of people have a good old fiddle with lol.

That's nothing. Found my friend had put some lights up in the shed using bell wire and coax insulated using sellotape! Seeing the hotchpotch cable festooned from the kitchen did make me go cold.

His reply "wire is wire"!