The question none of us asked, how long was the extension cord in servive before it failed?
that should read “in service”
Once again illustrating the deficiency in the electrical code and the UL listing process. It is entirely possible to start an electrical fire and never trip the breaker. Many flourescent light fixtures, and table lamps have wiring that is only adequate for the expected load in the fixture which might be a couple of amps. So they allow a big safely factor and put in wire rated at 5 amp. You plug this into a 15 amp receptacle, a short or partial short develops in the light fixture which draws 10 or 12 amps and Bingo! you’ve got a fire. Happens all the time.
We need to start a movement to demand that each appliance plug contain a fuse rated for the current the appliance draws.
Dave,
Aint gonna happen, what would be nice would be if we could buy fused or breaker enabled cords/w surge supressers on them.
What? we can? And to think all this time I ran my salt water aquariums directly off the wall.
Don’t they have something like this in the UK? I’d be in favor of such a scheme.
Am I right to assume that this is a two-prong cord, not a three prong with ground?
Regardless, I think that this is the time to break out some basic test equipment. I’m sure that prices and availability are different in Panama, but I can buy a digital Volt-Ohm meter in the States for less than ten bucks at a big-box store. If you can’t buy one, could you borrow one somewhere?
Starting at the wall, I would check resistance between the hot and neutral of the cord (also between hot and neutral and ground if this is a three-conductor circuit), then check the same for each of the appliances. Just as a guess, I’d expect each appliance to have a bare minimum of ten ohms resistance (remember, this is just a seat-of-the-pants guess; the actual value will probably be much higher.) I’d suspect anything with a resistance of zero to a few ohms. Actually, I’d just suspect the lowest reading I got until I could do the math.
Along with a meter, it would be a good idea to get an outlet tester. This is plugged into the wall and indicates whether the outlet is properly wired and gives a readout if it isn’t to show what is wrong. Sure, you could also test with a digital volt-ohm meter, but the outlet tester is a little safer.
QED,
“I’d be in favor of such a scheme”
For gods sake why?
Lets not get into GD territory here but how long do you figure it would take the general public to realize a blown fuse can be wrapped in aluminum foil?
Blade-type fuses are rather harder to defeat, which is almost certainly what would be used. As for why, it’s the precise reasons outlined by David Simmons. It’s perfectly possible to plug a UL listed appliance into a UL listed outlet with wiring and breaker protection per the NEC and still start a fire.
No disrespect meant cornflakes, but I think this one is beyond garden variety test equipment. Personally, I’d like to check the power source at point of connection (duplex), and then evaluate the group of appliances described by the OP as they were connected in the failure scenario. Voltage, amperage, and waveform.
The extremely low draw indicated by the connected devices is what has me doing the head scratch. Perhaps Colibri will indulge Q.E.D. and we’ll all learn something. 
As my sister said, safety schemes are not fool-proof, they are only fool resistant. Or as also has been said, they are not damned fool proof.
During all those years that fuses (vs. breakers) were used in the main panel, you could put a penny in the blown fuse socket and temporarily restore service. It happened and was a problem, but not a big problem.
I would disagree. I’ve done a tremendous amount of troubleshooting (much more complex than this, in fact) using nothing more than a run-of-the-mill VOM.
Skill is more important than tools…
I’ve sent you an e-mail. I can probably send it on Monday. I also have an identical cord that is still intact that I can send you.
Like danceswithcats, the thing that really puzzles me about this is the extent of the damage that resulted from what would seem to be a very low draw.
To answer a few of the other questions:
The AC adapters are warm but not excessively hot. Both the phone and answering machine seem to be working fine.
All the plugs involved are two-prong.
I don’t know how long I’ve had that particular extension cord; several years, at least, maybe much longer.
No email yet, but the mailserver has been acting up today. If I don’t get anything by tomorrow, I’ll give you an alternate address. You can send along the intact cord if you wish. It may or may not be instructive, but it sure couldn’t hurt to take a look at it.
The email from Colibri finally arrived, and when I get the cord, I’ll post the results of my analysis here. I’ll subscribe to this thread as a sort of bookmark.
thanks, I am looking forward to hearing the answer.
Yes we do, our plugs have a fuse installed, for many years users bought appliances without a mains plug on them and fitted their own, along with the fuse.
This was a rich source of domestic electrical fires, people very often do not have the very basic skill of being able to fit a plug and wire it correctly.
The problem here was that plugs sold loose have 13A fuses in them and the average person was either too ignorant or too lazy to bother locating and fitting the correct one.
Nowadays, following European legislation - which makes us have to change our rules to comply with the general principles, all electrical appliances sold must have a plug already fitted and with the correct rated fuse for that appliance installed.
The changes to the law have now made it clear that those who sell any electrical aplliance might well bear liability if certain checks have not been carried out(I’m not aware of any definative test case but it will happen someday), which means that you don’t often see electrical goods for sale in second user shops.
The law makes even charity shops liable these days too, whereas once they had a loophole due to their being a volunteer enterprise and used to not be considered a place of work in the sense of national insurance, taxation and employment law.
Many manufacturers have gone further, moulding the cable into the plug, which eliminates another common failing, that the screw holding the two halves of the plug together has been overtightened and damaging the thread, which makes for a plug that might fall apart when being removed from the socket, or plugs that are held together with sellotape.
In this case, what seems to have happened is a leakage to earth - a partial short to earth.
What happens is that a partial short develops near the adaptor end, at the point where the flex enters the free socket body.
The live wire has then to carry the normal supply current for the appliances, plus the partial short overload current.
The neutral is only carrying the appliance current, and the earth carries the partial short circuit current.
You do not need a large overload for this effect to happen, lets say the appliances draw perhaps half an amp, then the live will carry maybe 20.5 amps and that extra half amp can quite easily be the differance in heating effect that made that wire melt its insulation first.
Kudos to Q.E.D. for going the extra mile, and volunteering to receive and test the extension cord(s). I look forward to the results.
I now wish to serve official notice to the SDMB that I will not be accepting any body parts or tissue or fluid samples via the US Mail, FedEx, or any other delivery service. At any time. Ever.
Thank you.
QtM, MD
Wuss. 
No disrespect taken. There may be something more complex going on but I’d rather eliminate the simple stuff first. Besides, Colibri is more likely to have access to a VOM.
Q.E.D., kudos to 'ya for checking the cord.
Personally, my money’s on a short inside the fan. I just think that there is a better chance of the power cable getting beat up, and the fan is 110VAC from the plug to the motor.
But the fan (I’m almost certain) was off when the cord melted. And it seems to work fine now.