Has anyone ever seen an earth pin on a plug that looks like this:
I don't know where it came from but this little lead has caused me a serious amount of trouble.
I had it powering a Weller PU81 soldering iron (though it probably isn't the original lead) and have just found it to be the cause of the wildest of goose chases. I was working on a colpits oscillator circuit that developed a fault, found one of the two N=Channel mosfets faulty, replaced it to no effect. Traced the circuit up and down, removed the other N-Channel, found it faulty, replaced it to no effect.... rinse and repeat this cycle several times. At this point I'm sure its something in my circuit that's popping the mosfets.... so I build another... still popping mosfets.
So I start to question my components, BS170 from Farnell, test OK on the Peak Atlas component tester, no problems.
I suspect static, but Ive never had a problem with that, certainly not on this scale. The mosfets are popping on power up (or so it seems)
In desperation I fit then remove one before it's even powered up and find it faulty, at this point I'm sure its static but decide to test another theory..... I touch a brand new one out of the pack with my Weller and its faulty!!
I get out the gas Iron and fit two new mosfets, the circuit fires up instantly!
I test the continuity from the iron tip to the earth plug pin, it's around 25r Im not sure if thats normal, I always assumed a direct short to earth. Then I plug in and test to an earth point.... open circuit. I presumed a faulty socket, replaced it to no avail then noticed the insulation on the earth pin here. When I use another IEC lead the iron is earthed correctly (well 25r anyway).
I have never paid much attention to mains plugs but I dont recall seeing one with any insulation on, logic says it would be better without insulation surely. This fault was a massive hassle, but could have been much much worse.
The other question is whether the socket is also partly to blame, maybe a case of two substandard parts coming together to cause the fault?
I'm also wondering if there's a fault in the Weller as well, obviously it needs an earth for safety but in a non-fault condition shouldn't the tip just float? Note that the circuit I was working on was battery powered the entire time, totally isolated.
Edit -
I've done a little googling and it looks like this certainly is a fault.... probably a case of "sort by price" importing again.
http://www.bs1363.org.uk/I don't recall specifically buying IEC leads, I have loads lying around from various equipment so unfortunately I can't identify the source. Another one to be aware of