Round-pin sockets (2023 Update)

[Brian Gaff]

Yes that would do it. I did much the same with a simple old car battery once. Brian

[Brian Gaff]

Well anything thathad a winding in it did not work, so many autochangers did not work. Most radios that used Valves in those days had a huge dropper inside and live earth as they needed to generate heater and ht voltages somehow. I had a little bakelite valve radio with medium and long wave like this and it had two pointers on the dial with station names on the inside of the glass. It eventually made a hole above the dropper and was tossed. Bit lethal, as indeed were those with so called line cord droppers where the mains cable itself was the voltage dropper and hence you could not curl it up or shorten it without the thing catching fire. DC was all gone domestically by 53, due to the problems it caused. Brian

[Brian Gaff]

In an old copy of Radio constructor was a DC fluorescent light design, but it did as I recall, flicker a bit. I don't know about wearing out one end of the tube, Don't think anyone had thought of it. You could use it to transmit audio though, Worked better than ordinary lights, since there was less thermal lag. Oh the fun we had with the orp

1. Brian

[Scott]

I think I have seen the ones where the fuse acts as the live pin. I have looked at a few websites (including MK) and these plugs do not appear to have protected pins. This seems very surprising.

[Brian Gaff]

The p prefix of valves were specifically created for series heater chains. The normal audio amp valve was Ecl 86, but the series heater one was Pcl 86. Often to protect the valves at the surge of switch on, they also used a Thermistor as well.

There were a lot of TVs that only ran on AC that had live chassis, and the only way to run those safely was to use an isolation transformer and earth the chassis on its secondary side. That was how we engineers worked on them. Brian

[nib]

The early 13A plugs had all-metal pins as well. I still have one!

nib

[Brian Gaff]

Actually, most of the first colour sets had live chassis, and any audio outputs were via high voltage capacitors. Of course once transistors took over things changed a lot as it was only the EHT generation that was using high voltages.

Brian

[Scott]

Wikipedia suggests the change was in 1984:

August 1984: BS 1363:1984 "Specification for 13 A fused plugs switched and unswitched socket-outlets" published. This standard superseded BS

1363:1967. Changes include the introduction of sleeved pins on Line and Neutral, metric dimensions replacing inches, specifications added for non-rewirable plugs and portable socket-outlets. The standard was aligned, where possible, with the proposed IEC standard for domestic plugs and socket-outlets.

[charles]

Only one?

[charles]

The fuse in the plug variety were made by Dorman & Smith (known as D&S). They were a rival to the now standard 13A, The BBC used them for technical supplies for a time. They were stocked in Selfridges whch make me thinkthat some of mansion blocks around Marble Arch were fitted with them.

[Joe]

Rectangular pins weren't shrouded for many years, either. It may make a difference where the design of plug causes your fingers to curl around it as you pull it out, but I never got a shock off the unshrouded type.

MK plugs had a flange on the plug top which you pulled, so there was never a chance of touching a pin.

A lot of early sockets were unswitched, but I don't know if they are legal to sell now.

[Scott]

It looks like they are:

[charles]

I'm sure they are. TLC has them in their current catalogue including some made by MK.

[Mike Clarke]

There's no mandatory requirement for sockets to have switches. They're just there as a convenience - it's much more convenient to switch off instead of pulling out a 13A plug to be left lying on the floor to be trod on by bare feet. Which probably accounts for switched sockets being very much a British thing.

[Bob Eager]

We still had DC until the late 1950s; this was in Brighton (the changover was piecemeal).

Some parts of the town didn't change until 1965.

[Max Demian]

I don't think many TVs had any kind of audio output. There were b/w portables that worked off mains or 12V DC (for caravans) and my 1978 Sony CTV which had earphone sockets.

[Max Demian]

I think that the negative of DC mains was more or less earth potential, and you had to put the 2-pin plug in the right way round for it to work.

With AC mains you could plug it in either way so the chassis could be live.

[Scott]

How did you know which was the right way round? Were there any three pin plugs in DC systems?

Same as DC then?

[John Walliker]

I added audio outputs to a few Decca colour TVs using an isolating transformer. These were valve/transistor hybrids with a live chassis. I think I took the audio from the FM discriminator and applied de-emphasis before the transformer driver. As far as I know none of them had official audio outputs. We used Decca because a friend was a manager at the factory so we could get staff prices. It was possible to get service manuals with complete schematics and realignment guidance in those days. In the end, Trinitron tubes were so much better than most conventional shadow mask ones so we switched to Sony despite the higher cost. John

[Scott]

Our radio repair man added a switch to allow the speaker to be turned off while recording via the 'Aux' output. This was a GEC valve radio. Some time later, the radio failed. Did he (Mr McLaughlin) break it?