Scott:

> As a matter of interest, what appliances or equipment could not be
used with DC?
> I assume all heating equipment (cookers, radiators, kettles, irons
etc) would be okay but with heavier duty switches.
> I believe radios could be AC, DC or dual standard. Gramophones I
assume were similar.

Grams usually used a synchronoous motor, so no dc. Some old ones used a motor with centrifugal governor, ok on ac or dc, but less accurate speed

Universal or live chassis radios were fine on dc, if the plug was in the right way. Transformer sets not.

> Were incandescent lightbulbs the same or were the DC ones different
because the current would be continuous and not alternating?

same. The filament is just a heating wire.

> No
fluorescent lighting, I assume.

Flourescents were run on a resistor ballast on dc, less efficient.

> Were different motors needed for vacuum cleaners, washing machines,
fridges etc? Could they be dual standard?

Universal motors worked on either. Induction motors, typical of fridges, didn't. Gas fridges were one option, ammonia cycle fridges another, many of course had no fridge.

> Was rewiring needed or could it be assumed if the cables were suitable
for DC they would be equally suitable for AC? Did DC have an earth
cable?

no major difference in spec

nib:

> And also the knobs on the front were often just fitted to
> possibly live metal shafts, relying on just the bakelite knob for
> insulation. Sometimes they were even just clipped onto the shaft so you
> could pull them off and touch live metal. The other external touchable
> metal, the aerial socket, was isolated by capacitors.
>
> Good old days, hey! Electrical safety has come a long way.

the worst were knobs with grub screws. Some were recessed, some not. The 'not' grub screws often came close to the knob surface & were insulated with a bit of wax. Time & inevitable repairs meant the wax was lost, and any slight wetness of hand would connect you to the often live grub screw. Ditto if the grub was replaced with one slightly longer, and that happened often enough.

Brian Gaff:

> 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.

curtain burners

Brian Gaff:

> In an old copy of Radio constructor was a DC fluorescent light design, but
> it did as I recall, flicker a bit.

dc supplies were in reality rectified multiphase ac

> I don't know about wearing out one end of
> the tube, Don't think anyone had thought of it.

of course they thought about it, fluorescent lighting was a thoroughly studied subject by the 1940s

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.

IIRC there were actually 3 standards created in the 1940s: BS1363 that we still use, D&S & I think the 3rd was Wylex.

Joe:

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

they are. Good option for freezers etc.

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.

The Sonys used a small audio transformer just for the earphone socket

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.

50% of customers got grounded -ve, 50% got grounded +ve. 3 wire split phase transmission is cheaper.

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?

little or no load on the secondary causes high voltages on the anode, as the transformer acts as a choke. It can cause failures.

Bob Eager

> We had 2A, 5A and 15A plugs/sockets on our DC mains. All 3 pin. But we
> also had 2 pin 2A ones for lamps etc.

2 pin 5A were common, both for wall sockets & appliance leads. Was it BS372? There was also a 2 pin 15A in the standards, though I don't remember seeing one. I think kettle leads were a derivative of it, adding side contact earthing.

Scott:

> Was it also necessary for DC switches to have a spring to prevent
arcing?

yes

> I remember in our house some of the sockets and light
switches were far more substantial than the newer ones.