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 , "Gary
KW4Z" wrote:


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.

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.


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.

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.

Looking at the power cord's plug, the tip of the prong that got the
zap, is a bit black and melted.

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.


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?

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



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. .

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.


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.)

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


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.

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.

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.

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


Ideas on what may have happened and how do I fix it?

Most importantly though, any damage being done to the computer?

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.



--more threads on my old house wiring, coming.

Bob T