Possible under-voltage issue?

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Old 07-24-16, 08:15 PM
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Possible under-voltage issue?

I'm having a strange issue in my apartment where my laptop will suddenly not charge on one of the circuits. There are 3 circuits in my apartment - one for the kitchen, one for the bathroom, and one for the rest of the apartment. The laptop will not charge on the main circuit but is fine in the bathroom or kitchen. The building was built in 1901 as a single family home and converted to 5 apartments in the 80s. Electrical work is probably not compliant with code. Also, it is very hot here at the moment and the electrical grid is stressed.

Could it be an issue with the voltage being too low (or high) on the main circuit? I know my friend always comments on how slow his phone charges here and suspects it is due to under-voltage. No other electronics seem to have any issues though. Could it be an issue with the transformer brick for the laptop?

My other thought is that it might be a harmonics issue, although I'm not very knowledgeable about that.

Any tips for how to determine the cause? I ordered a multimeter which should be here in a couple of days and I know how to use it for basic funcitons, but I'm not really sure if there's anything I should do but check the voltage at the outlets around the house. Can a multimeter be used to determine if there is an issue with harmonics?
 
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Old 07-24-16, 08:28 PM
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Most laptop and phone charges are of the inverter type and work even if the power is lower than normal. I think most laptop chargers are listed for use from 100-240v. So your circuit would have to be very low to affect it.

I don't think you have a harmonic problem in a residence. Your best course of action is to wait for the test meter and check the individual circuits.
 
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Old 07-24-16, 09:13 PM
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I ordered a multimeter
Digital or analog? Generally cheap analog meters or less likely to give you misleading readings than low price digital meters. I don't know how much you spent but an $8-$15 analog meter should be fine for just measuring voltage.
 
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Old 07-27-16, 05:26 AM
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Do you have any incandescent lights still in use? Does the brightness vary depending on which receptacle you plug it into?

Does the laptop itself work (internet, word processing, computing) using a receptacle it won't charge using?

Varying voltage on the grid or from a local pole transformer will affect all circuits in your home the same way.
 
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Old 07-27-16, 07:53 PM
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So I got the multimeter. Voltage at all outlets is the same - 120v +/- 0.5 V.

The strange thing is on the DC side of the adapter. When I'm plugged in in the kitchen or bathroom, I always get 19.6V which is what the brick is rated for.

However, when I plug in on the main circuit, weird stuff happens. I initially get 19.6V. However, when I plug into the PC, the PC seems to get power for an instant then stops charging. If I then pull the charger out, I'm getting like 6 volts which drops to zero eventually (quickly to around 1.5 v, then slowly to 0). Now here's the super weird part: If I then unplug the AC side of the adapter, the voltage returns to 19.6. Is this possibly and indication that there is something that is causing the charger to ground?
 
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Old 07-27-16, 09:37 PM
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When you check the voltage at the receptacles..... plug something into the other half of the receptacle like a table lamp. Something to place a bit of a load on the circuit. Then recheck the voltage with the load plugged in and turned on.
 
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