Changing a mains lead

[Graeme]

Been playing with an old toy train transformer/controller (H&M Powermaster, for those with long memories), circa 1960, 0-12v DC output, up to 2.5 amps. The mains lead, woven outer (like an iron) contains rubber covered wires (old colours, of course), and the rubber has perished.

Changed for a modern flex, but the original earth was soldered directly to the all metal chassis. I have soldered a tag to the earth, and attached it to the chassis with a nut, washer and bolt. Metal all cleaned and shiny. Hope that is OK?

Curiously, although the mains lead was rubber, all the internal wiring is PVC, and looks fine. Probably constructed about the time rubber flex was being replaced by PVC?

[Brian Gaff]

Yes sounds like an old iron flex. Interestingly though most of my old train and slot racing transformers had pace cables and those mostly did the earthing via a tag under one of the transformer fixing bolts, with a strain relief elsewhere to stop rotation and pulling moving it. The airfix ones were very good with hammer finish metal boxes, shame their controllers tended to melt after a while though. The train controllers seemed to be wirewound pots in a plastic box with a cut out button that pinged if there was a short. The transformers were in plastic as well, at least the Triang ones I had were. You could make a good psu with the airfix ones as plenty of room for some capacitors and a voltage regulator bolted to the case. The volts if bridge rectified instead of that naff metal one they used was 16 v. Brian

[John Rumm]

Coo that's posh... I had a H&M Safety Minor - one big rotary control and a half wave switch, and not much else!

ISTR it became my experimentation PSU of choice (because it was all I had) when I first started dabbling with electronics and electrics.

Yup, sounds fine.

Yup PVC was commonly available by the 60's

[invalid]

If you are worried fit a RCD plug on it.

[Harry Bloomfield, Esq.]

Graeme laid this down on his screen :

Iron flexes were always rubber, probably still are, more heat resistant than PVC - but I have no idea why on a power supply. Maybe they bought a cheap batch?

[Dave Plowman (News)]

Yup.

Dunno why they'd have used that type of mains lead. Perhaps they had plenty in stock?

[Dave W]

I thought cloth-covered mains lead was used for everything irrespective of whether it was necessary.

[Dave Liquorice]

Flat or shake proof washer? *Very* slight chance that a flat washer could allow the joint loosen.

[tabbypurr]

Any washer can. shakeproofs aren't.

NT

[Graeme]

Not shake proof :-(

Temporary hiatus. Wife now home from hospital, but that seems to give even less time for toys! Add in son now home from uni for a week, and one of his friends visiting us in a couple of days, time is tight (as Booker T would say).

Back with photos later.

[Dave Liquorice]

chassis

washer

Wouldn't loose any sleep over it in this instance, assuming the nut anb bolt were well tightened.

[Dave Liquorice]

washer

Fascinating. Though only a split spring washer was tested not a shakeproof one. This one does split ring and shakeproof and they turn out pretty much the same:

[Graeme]

Yes, well tightened. The unit itself is unlikely to be moved during use, and the incoming mains lead is firmly held in a grip, within the unit, so should be OK.