Cord cut. How do I determine which wire is hot and which is neutral?

[5to1baby1in5]

Originally posted by: mrSHEiK124
The DVD player at my grandparents house overseas always shocks me through the chassis when I try and push a button on the unit. Plugs in Israel aren't polarized unless they have a ground prong, and the DVD player only has a two prong cord; think that might have something to do with it?

Does it do it every time, or just when you walk across the carpet and touch it the first time (static electricity)?

Recommend you don't touch this device while dripping wet.

 

[DrPizza]

Originally posted by: 5to1baby1in5
This is not exactly correct.

Yes, the device will still work no matter what the polarity.

The Neutral, however, will be at the same voltage as ground. You could touch it while grounded and not get zapped.

L1 (hot) oscilates between +120 V and -120 V relative to the neutral. If you touch it while grounded, then you will get shocked.

L1 is supposed to be wired to a power switch incase the device shorts out internally, you will not be sending power to the chassis when it is turned off. If it shorts internally while turned on, then it will blow the breaker.

In this case, the AC power goes directly to the main board and to a DC power supply. The DC power supply is most likely energized all the time, and is switched on via a DC power button. In this case, it may not matter how you wire it.

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If you look at a lamp chord, then you will notice the insulation has a ridge along one of the wires. This helps you track the polarity of the wires. The ridge is supposed to go to the wider prong (Neutral). Check your chord for this ridge. If it is there, then you will know which wire is L1, and which one is Neutral.

:thumbsup:
"Polarity" doesn't matter on a lot of appliances, and I'm not sure about blu-ray players. But, on some things, it certainly does matter as far as safety is concerned. The first example that comes to mind is power tools. Many are two prong, but with the wider blade for the neutral to protect the user. In the case of a short, the chassis isn't hot; instead, when the tool is turned on (the switch/trigger is for the hot), the short leads to a breaker tripping. (Unless, of course, you're standing barefoot on a basement floor, in a puddle of water while using the tool, creating an easier path to ground than through the neutral wire.)
Though, the probability of such a problem in a blu-ray player is incredibly tiny.

 

[futuristicmonkey]

Originally posted by: Shawn
I will be getting my hands on a blu-ray player tomorrow with a cut cord. Soldering in a new power cord will be easy, but I want to make sure I get the polarity correct. I don't have the original cord for reference. I'm guessing it'll be written on the PCB correct?

Here is the best pic I could find. Would blue be hot?

Check the resistance between the metal case and both of the wires. Make sure to scratch the metal to be sure of a good connection. If you find a negligible resistance between a wire and the chassis you'll want to connect that wire to the neutral. The neutral is typically identified by the wider slot on a plug.

Edit: If neither of the wires is continuous with chassis ground, then it does not matter which way you connect the cord.

Further, if you have a "good" (brand-name) multimeter, you can typically find out which slot of the plug is actually the neutral. Basically, insert the red probe into each hole and see what kind of voltage reading you take. This is called ghost voltage. The slot with the higher voltage is the "hot" one. This is a decent way of checking the outlets in your home for reversed polarity.

 

[futuristicmonkey]

Oops, wrong button. 😱

 

[Special K]

Originally posted by: 5to1baby1in5


L1 (hot) oscilates between +120 V and -120 V relative to the neutral. If you touch it while grounded, then you will get shocked.

Just a quick clarification, it oscillates between +170 V and - 170 V. 120 V is the RMS value:

170/sqrt(2) = 120

 

[Shawn]

Ok, I just got it and on the outside of the cord there is a white line on the side of the blue wire. I guess that's the neutral.