Plug sockets

[johnpriceuk]

In the photo, it appears to be teo different cables but on further inspection it's just one, it was originally black but a portion has been painted white. Same deal for the speaker on the other side which has an identical arrangement.

Yep I guess you're right, it's probably a 100v feed from an old power amp somewhere as they definitely look like cheap passive speakers to me.

Not too important I guess as these speakers are fixed installation but I wonder what would happen if someone stumbled across this speaker with the mains plug attached and managed to find a 240v socket or an adaptor to plug it into a modern socket!

[julie_m]

So it's all just one cable? That makes a lot of sense, then. The speaker didn't look like a powered one.

I suppose the idea of the round-pin plugs and sockets was to use a connector that is sufficiently unusual for nobody ever to be likely to plug a speaker inadvertently into the mains. They may even have been rescued from an earlier rewiring job .....

[Nickthedentist]

The plug and socket look pretty ancient to me, whereas the speakers are modern, so presumably are not original to the installation.


Nick.

[Lucien Nunes]

I see this in a number of places, my primary school was the first. There were four 2A 3-pin sockets parallel connected, wired in pyro. Two in likely positions for the source and one either side of the stage proscenium for speakers. I remember the arrival of the new-fangled Sanyo music centre, and the headmaster wiring it in. I watched him wiring two DIN speaker plugs to the one 3-pin plug, explaining as he did so that he had tested for continuity between the speaker output -ve terminals on the two channels to prove that the outputs weren't bridge driven and could have one side paralleled. Decent chap he was, always had time to explain and discuss.

There was another 2A 3-pin socket on stage for the input to the 100V line system that ran throughout the school. That had C&S continental-style outlets but for some unknown reason the socket used for input was 3-pin.

[BGmidsUK]

I have an ivory example of the first in post 65 in my back bedroom. Someone had connected it in to the new ring main using a 5-amp rated junction box, the thick steel cable prevented the screws fitting in the terminals and one had fallen out altogether, found amongst the lath said junction box was resting on (kindling?)

This was put right and is still in use nearly two decades later.

I'll see if I can get in there with my camera, there's currently a TV in the way!


Brian

[Rhgbristol]

Some more info on MK history, based on my 40 years plus electrical installation knowledge:

Mk changed from Ivory coloured Bakelite to white, in about 1973.
Mk round edge sockets / switches went to square edge 'logic' range in 1975
This square edge logic range changed to current 'logic plus range' in 1995/96
The 646 safety plug went to the sleeve pin variety with wedge cordgrips in about 1972
In the period 1972/1974 mk made a range of sockets where the screws bore down on a plate which then clamped the conductors - as a measure to work with the aluminium cables we in the uk had to endure at that time, due to copper shortage. It was found that traditional screws would just chew straight through such relatively small aluminium conductors.

[Rhgbristol]

Ref screw sizes
The original flush bs1363 standard accessories and associated backboxes, used 4BA gauge raised head screws.

When the electrical industry went metric between mid 1969 and late 1972, the standard changed to M3.5 size, which is slightly smaller and a different thread pitch and angle to 4BA

[johnpriceuk]

Interesting selection of old sockets on this site... I've included an image but all credit to http://riverview.scotgate.org/?p=23

I'm thinking of starting a blog of photos of interesting sockets spotted still in-situ out and about, user submissions will be accepted of course!

[dseymo1]

Originally Posted by Rhgbristol

Some more info on MK history, based on my 40 years plus electrical installation knowledge:
Mk changed from Ivory coloured Bakelite to white, in about 1973.

To correspond with the introduction of 'brilliant white' paint, perhaps?

[julie_m]

Originally Posted by johnpriceuk

I'm thinking of starting a blog of photos of interesting sockets spotted still in-situ out and about, user submissions will be accepted of course!

Excellent idea! Be sure to post a discreet link if / when you do get it up and running .....

[Refugee]

Have a look at these.
NOS Bakelite ones no less.

[Herald1360]

Just the job for a vintage extension lead!

[Refugee]

I had been keeping an eye out for a couple of un-switched sockets for some time for use on my bench for the isolating transformer output.
I also got 10 NOS modern doubles for £1 for my test equipment bays that have started getting short of sockets.

[Skywave]

Originally Posted by Refugee

. . . a couple of un-switched sockets . . . for use on my bench for the isolating transformer output.

If I have understood that correctly, you intend to have the O/P of a mains isol. transformer feeding two sockets, presumable wired in parallel. In some quarters, that practice of two outlets thus wired is frowned upon as a potential safety hazard.
You are probably well-aware of that, but others reading this thread might not be.

Al.

[Herald1360]

That's odd-the big blue Carroll & Meynell lump I run my shed from has just that- two parallel output sockets, one either side of the box.

[Refugee]

You are right.
The Bakelite sockets are single and un-switched and are ideal for the job.
My big Variac is wired in parallel with the socket for convenience so I do have to take care with that and if two power supplies are required I have another smaller Variac and isolating transformer for a second isolated supply.

[ms660]

There could be a problem if an ac/dc chassis is connected to one socket and another one connected to the other socket if one of the ac/dc chassis has the plug wired up wrong.

There may be other scenarios?

Lawrence.

[Refugee]

Well the isolating transformer is just that and an AC/DC chassis will only be on test as a single unit adopting its earth from any item of test equipment that may be connected. Once complete the unit will have the covers on and there will be no problem.

Perhaps the Variac could be wired with a double pole change over switch so that only the socket or the the Variac itself is live at any one time?

[ms660]

To avoid any confusion I was referring to post#94.

Lawrence.

[Refugee]

Yes post 98 was in response to yours and post 94.
The set-up is a large isolating transformer under the test gear rack with a steel double socket attached and the Variac plugged permanently connected to one of the sockets.
If I do not want the Variac powered an extension lead has to be used by reaching down under the test gear rack so the level of difficulty makes an accident very unlikely.
Running isolated power up to the front of the test gear rack and fitting the double pole switch and socket would make it easier.