My old house wiring -- Sparks flying, plugs dying, computer being destroyed?


History:
In a ealier topic, I wrote of my old house, built in 1952 + remodeled by someone who knew even less than I. It has no grounds and is a general mess, I think even according to code back then -people tell me the electrician and the building inspector were "friends."
Thirty years ago, when I bought this house, the person inspecting it as well as myself saw the standard, three prong, grounded outlets and thought all was okay; but he didn't check to make sure they worked and I was too young to know to tell him to. After all, he was the inspector.
It wasn't until sometime later; when I found a few, two slot, non-grounded outlets, I became suspicious. And my suspicions are correct. Someone replaced nearly all the outlets with three prong, polarized, grounded ones, but no ground to connect them to and no way to fish a ground to them.
Here's Today's problems and a few questions:
I got a laptop computer for Christmas. It uses an AC to DC adapter (transformer) to get power and recharge the computer's batteries.
Unlike most modern electronics, this one has a non-polarized socket for the charger and the power cord is non-polarized, non-grounded too. Neither is there any kind of marking, such as a white stripe along the cord that lets me know which is the hot/neutral side. From what I've read, a white stripe usually indicates it is the polarized side (the neutral) and goes into the longer slot on the wall socket. The longer slot is always neutral. Is that right?
The instructions say, plug the charger into the computer and then that into the wall socket. When I did it, there was an arc from the wall socket's left slot. I thought that's strange. (This is one of the three prong, polarized, grounded (but not really) sockets.)
I left it plugged in for a day or so. I unplugged it. Later, when I plugged it back in, without paying attention to the orientation of the plug, there was no spark. I thought, "strange," again. So, I flipped the power cord plug over, plugged it in that way and sure enough, a spark from the left slot of the wall socket. --bright blue and snappy.
Obviously, the left (tall) slot of the wall socket is hot (which I think is backwards according to code?). And with no white stripe on the power cord that plugs into the transformer, then no polarized socket on the computer: two round holes, instead of a square and round, I can't tell which is hot/neutral and what should go where, but I sure didn't like the arc at the wall socket.
Looking at the power cord's plug, the tip of the prong that got the zap, is a bit black and melted. Of course, I don't want to destroy the very expensive computer.
1) Does it matter which way the power cord goes into the outlet? With nothing polarized, I don't know what to do. Or does it matter?
Spark, no spark? destroy my computer or is it okay, no matter which way it goes into the AC?
2) Further checking the wall sockets, looking at them from the front (ground down), I find some take a polarized plug's neutral prong, (I think that the wide one), fits into the wall socket's tall, left slot; for others wall sockets though, the tall slot is on the right. .
I assume that the wall sockets that take it on the right are turned upside down, so no harm done-as long as it's wired correctly. (I'm off to Lowes to get an outlet checker.)
3) I tested a three prong, polarized, grounded (but not really), duplex socket with my VOM (battery powered) for voltage. I pushed one probe into the short slot, the other into the long (left) slot.
When I put the probe into the left slot-Pow! A nice, blue arc from the tip of it into the slot. I tried it again and the same thing happened. I switched the probes-no arc. I was surprised by that since I thought with AC, as long as the VOM is set to AC, it doesn't matter which way the +- probes go.
Since the arcing distracted me, I failed to get the voltage. I tried my VOM once more.
This time, when I put the probe into the left slot there was a big flash. My VOM went dead-is dead-- and so is the wall outlet. Now, I have to go by a new VOM, new wall socket. Funny that the fuse didn't blow in the VOM nor did a circuit breaker trip.
Ideas on what may have happened and how do I fix it?
Most importantly though, any damage being done to the computer?
--more threads on my old house wiring, coming.
Bob T
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Breakers or fuses? If breakers how old? If it's the original stuff, it's too old and you need a new electrical panel. And most likely some more circuits. Is the wire run in armored cable? If so then you do have a ground and can most likely just use that as your ground.
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Sounds like you have your hands full............thats for sure. If using a VOM.......be sure to set the dial to the desired range first and be sure that the probes are in the correct meter slots for checking AC. The different settings have different impedances. But you are correct......you should be able to put the probes in either slot.
What you are stating makes no sense at all to me.......I am not an Electrician....but an Engineer in a Hospital setting. What do the other outlets do, read?..the same thing....spark?? Sounds like maybe you should rewire the whole house properly with new breaker box and get it over with. If the probes and/or computer plug melted....then the fuse or breaker should have tripped.......no? Thats alot of current to melt metal!!
You should run the proper wire yourself to save a few bucks, then have the electrician hook it all up to the new box. Definetly worth it in your case. Sounds like a future house fire is in the making here.
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stars1234 wrote:
Deleted some of the history.

Correct. However, a polarized connection is not necessary for the charger. It does not know the difference.

Now that worries me.

Arcs should not happen under any condition. The presence of an arc has no relationship as to which line is hot. That is unless you are shorting a ground to the wires.

My thoughts are that there is something wrong with the socket. Perhaps a loose wire.

No. It should not make any difference.

Orientation is not important. What is important is how the sockets were wired. If your wire has the proper color code the hot should be black and the neutral should be white. Black connected to the narrow slot and white to the wide.

Correct. No problem

Not a good test. You should not be drawing any current to speak of through your meter. That is unless you have it on a current measurement setting. Then I would expect you would blow something.

You blew the line open before the circuit breaker had time to trip.

I would hold off until I find out what the voltages are doing.
I think you must have had a short inside the VOM all along.
To verify which line is hot and which is neutral I would us a jumper to get the negative lead of my vom hooked to a ground such as a water pipe. Then you should read 110 on the hot line. If you are using a high impedance meter you might see some voltage on the neutral but not very high.
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Rich256 wrote:

Could be charging blocking cap and is causing some. Or perhaps the reversing polarity is discharging a cap when into the neutral which is at ground.
...

Are you sure it didn't blow the VOM fuse? Normally they would only be a fraction of an amp. I'd double check it.
My bet is w/ the likelihood you were either on a continuity or current or input range by accident.
Except for the floating ground introduced w/ the use of a grounding outlet w/ a two-wire service, there really isn't anything so bad-sounding on the house here except it sounds like there might be crossed neutrals and hots if the receptacles weren't installed correctly (or at least consistently). I'd do a certainty check on that for all of them and I'd do it visually rather than relying on an inexpensive tester -- I've seen cases where some weren't terribly reliable.
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dpb wrote:

means something really wrong. Either a short in the meter or on something like the 10 amp scale.

And even if they are crossed it should make no difference for most appliances. Danger is that some things such as lamps could end up with the outside being hot. But even they are insulated. In the old days you could end up with a radio chassis being hot. No polarization at all in those days either.
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stars1234 wrote:

Others have addressed the meter issues and the probable outlet issues so I'll stick with just the computer issue.
A laptop "line lump" power adapter does not care at all which of it's input leads is hot and which is neutral. Further, most any new laptop line lump is auto ranging and should list something like ~100-240V 50/60Hz as it's input rating.
You may well get a small spark when plugging the power adapter in as it's going to have an initial surge on power up (regardless of whether the laptop is on or connected since the power adapter is always on.
If the adapter is indeed auto ranging as noted, there is nothing you house wiring can do to damage it since the worst your wiring can do is provide 240V to a 120V outlet which is bad for many items, but the laptop power adapter would happily auto range to and operate just fine.
Pete C.
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The side that sparks has nothing to do with which side is "hot". It merely indicates which side makes contact last, or breaks contact first. You could try replacing the outlet with a new "spec" grade outlet. Avoid the cheap outlets.
Bob
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The power adapter doesn't care how you plug in the cord and it is transformer isolated from the computer. To DC a Transformer is a short and for a moment to AC it's a short but only for a moment. It's not uncommon to have a small arc when plugging in a computer transformer, no matter the orientation of the plug. This is especially true when the computers battery is discharged, that is the spark will be more profound, if there is one.

You can't be sure of this just by observation. Where you do have grounds they and the neutral should be at the same potential, talking about 110VAC now.

That concerns me a bit, not because it's showing black from an arc but melted? Melted does concern me a bit. Could be you are plugging it in very very slowly over and over but I doubt that would even cause that.

Shouldn't matter due to the isolation of the transformer and power adapter.

If the grounding lug is on the bottom then the longer slot (the Neutral) should always be on the left and the shorter slot (HOT) always on the right. If a ground is hooked up correctly, extending back to the panel box, then with a volt meter you should measure 110 VAC from the Short slot to the longer slot and also 110VAC from the short slot to the grounding slot which is the hole or almost round hole. From the Longer Slot to the Ground hole there should be negligible voltage almost zero.

If it's a outlet without a ground plug hole that might be the case.

Any Volt Ohm meter when measuring Voltage, with the leads correctly inserted in a working and non-faulty meter should never cause an arc or pop or any sound. If the leads however are plugged into the slots for measuring AMP's (Current) then you are putting a SHORT CIRCUIT (which I feel you did) on the meter. Don't worry the reason you didn't have it happen again is that you BLEW the fuse on the inside of the meter. You have to have the probes from V - Voltage to the Ground lead of the volt meter. Some meters may use the same two holes or connections for every reading (current, volts, & ohms) but that is very dangerous. When you place your meter in AMP's or current measuring Amps then you have a direct short across those leads and that will cause any outlet to Arc and a loud pop until the meter blows or the breaker trips. My bets are the meter frys or the fuse blows. Better check that meter's fuse in the current lead. If only two slots your meter most likely isn't working very well now.

I'm surprised also -- Still wonder what terminals you had the probes plugged into and if you had the meter on Amps or Voltage.

Find a working meter, perform Voltage checks with the leads in the correct plug locations on the meter and if you have 110VAC on the outlet the computer's power adapter shouldn't care.
Mind you mine, like everyone else's is just an opinion based on each of our experiences so you have to make your own and best decisions because it's your computer and you are the one there and know best what's going on and what you did.

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One other thought or caution ... Make sure someone didn't wire the outlet for 220 Volts .. If so that could definitely cause your computer and power adapter problems .. Aka do I see smoke?
On 12/28/06 6:00 PM, in article C1B9B6B0.162A7% snipped-for-privacy@charter.net, "Gary

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Gary KW4Z wrote:

The one thing your missing though is laptop supplies are not usually a transformer, they are typically a switched power supply otherwise they would be much larger and heavier. A typical switching power supply will switch the hot side on and off thousands of times a second and very the pulse width to get the proper output voltage. I oversimplified but I hope you get the idea that since there is no transformer the characteristics will be different.
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wrote:

I can only suggest a computer solution. Unless you have some exceptional warranty that covers damage you may get (from 50's wiring). I would advise something like:
http://www.apc.com/products/family/index.cfm?id #
In a network environment once; one saved me during a "brown out". It protected from the drop and surge in power.
Good Luck. -- Oren
"Well, it doesn't happen all the time, but when it happens, it happens constantly."
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