Moulded mains plug failure

Hi, I've got a vintage Scope soldering iron, direct 240V connection (no transformer, the cord goes straight into the iron). It dates from early

80s IIRC, and has given faithful service over all this time. No model number marked so I can't provide it here, it has a red handle. Recently it stopped working, to my surprise the problem was at the plug end of the cord, not the iron end. The element resistance is fine, and the element to shaft resistance is off the scale (haven't meggered it).

The mains plug is moulded and sealed. For all 3 leads including earth, the resistance from the plug pin to the associated lead is erratic, varying from many K to many megs. Might there be some sort of protective device built into the plug, such as fusing? Strange though that the earth wire continuity has gone. All in all it sounds like a straight age failure, just wonder if there's something else there that I should be aware of. Any suggestions on possibilities? TIA

Reply to
bruce varley
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The wires have broken, a fairly common problem on moulded plugs.

Reply to
Davo

If you are really interested perform surgery and cut the rubber off with a stout knife and investigate if there is something strange tell us

Reply to
F Murtz

That's a common problem, the wires have simply broken through fatigue, there is almost certainly no protection device in the plug. Just replace the plug. But personally I wouldn't bother, bin it and get a proper temperature controlled station.

Dave.

Reply to
David L. Jones

...and AFAIK, you should NEVER, under any conditions, have less than close to zero ohms continuity between an earth pin and the frame of an appliance...

Reply to
MoiInAust

But you should get less than one ohm if you measure between the earth and neutral in a GPO socket.

Reply to
Davo

In the early days, it was common to cut off ANY moulded plug (from new) and replace it with a standard aftermarket plug, there were that many failures. One I remember was a

70's vintage Hanimex fluorescent desk lamp where moving the cord around near the plug caused the light to go on and off.

Other problems with moulded plugs from that era is the cord outer sheath coming free from where its attatched to the entrance to the plug, exposing the coloured wires inside. While the plug will still work, its not very safe.

The few moulded plugs I managed to hack apart years ago typically used spot welding or direct crimping to the pin to make the electrical connection. Obviously it isn't good enough in some cases.

Reply to
kreed

On Mon, 29 Dec 2008 07:23:48 -0600, bruce varley put finger to keyboard and composed:

AFAIK British mains plugs (not the moulded type) protect the active wire with a user replaceable fuse. I doubt that your plug is anything out of the ordinary.

I've had to replace the mains cable on my old Micron temperature controlled soldering station twice, but then I'm in the habit of packing my iron away after each use. Both times the break was at the iron end. BTW, I've since dropped the hand-piece and fractured the ceramic element inside, so if anyone needs the unit (cat # T2441, 60W) for spares, they are welcome to it.

- Franc Zabkar

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Reply to
Franc Zabkar

I think the point he was getting at was the the earth could fail first, and you'd be blissfully unaware of it until the fatal shock.

Hence ELCBs / RCCDs should be mandatory in ALL installations.

Graham

Reply to
Eeyore

Eh ? What has that got to do with the price of fish ?

Graham

Reply to
Eeyore

I bought an inexpensive but decent looking 4 way extension lead from a local supermarket some years ago.

It didn't 'feel right'. I examined it and no, it wasn't welded but used standard screw down connections made by cheap Chinese workers.

The thing that 'didn't feel right' was a single strand of copper wire attached to the live connection of one of the outlets that had 'missed the hole'. I corrected it.

Heads you lose, tails you lose.

Graham

Reply to
Eeyore

The moulded type also have fuses inserted from the 'bottom face'.

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However I did once find ONE with no visible fuse. Maybe it was internal and 'one-shot' ?

It's great to have the safest electrical system in the world !

Graham

Reply to
Eeyore

As opposed to shoddy British labor?

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Reply to
Michael A. Terrell

The safest system is the one that was never built.

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Reply to
Michael A. Terrell

I'm sure you could contribute very positively to that.

Graham

Reply to
Eeyore

Certainly. Anyone could. by following any of your rejected designs.

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Reply to
Michael A. Terrell

On Wed, 31 Dec 2008 12:25:45 +0000, Eeyore put finger to keyboard and composed:

All other things being equal, I would have thought that a 110V system was safer than a 240V system.

As for mains plugs, the safest ones I've seen are those with an integral ELCB. Maybe one day they'll be mandatory ???

- Franc Zabkar

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Reply to
Franc Zabkar

I recall a friend telling me of the US electricians up near exmouth who installed the VLF submarine comms system many moons ago, they had the habit (in USA) of wiping one of the wires across the back of the hand, ostensibly to find the active - from the inevitable reaction etc, Few yelps when doing that over here...!

Along with the intelligent power coupling (trekkie talk for mains socket), which has optical fibre, other voltages, choice of mains source etc etc...

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Reply to
Mike

NO design of mine has EVER been rejected. In fact I've turned design failures into commercial successes.

Don't believe me ? I'll get a PhD to send you an email.

Graham

Reply to
Eeyore

Why ? Both are lethal voltages and 120V as it actually is requires twice the current carrying capacity with 4x increased I2R losses and hotter conductors that catch fire more easily.

Give me even ONE example. Aside from British.

It seems to me you know little about electricity. Besides, about 90% of the world uses 220-240V. As ever it's the USA that's the BACKWARD IDIOT.

Graham

Reply to
Eeyore

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