Kind of a different question...

[budm]

Re: Kind of a different question...

Did you set to AC Micro Amp scale?

[EasyGoing1]

Re: Kind of a different question...

your meter is not showing it right - i'v seen that with flukes before, i think they filter out high frequency stuff.

60 Hz is ... high frequency?

[EasyGoing1]

Re: Kind of a different question...

Did you set to AC Micro Amp scale?

NO, I did Amps and milliamps and figured if I couldn't see any milliamps ... why would I go fishing for microamps? Just didn't make sense at the time ...

[EasyGoing1]

Re: Kind of a different question...

Did you set to AC Micro Amp scale?

And of course, because you brought it up, I went and checked also for microamps on the AC setting and I got ZIP! Yet when I switch to AC voltage and put the terminal back into the voltage port I still get a solid 6 volts

[stj]

Re: Kind of a different question...

humor me - try it with other meters
or scope the laptop casing!!! - no need to use the ground-clip

[EasyGoing1]

Re: Kind of a different question...

humor me - try it with other meters
or scope the laptop casing!!! - no need to use the ground-clip

Here it is ... scope lead hanging right off the case ...

[stj]

Re: Kind of a different question...

wow - that's a nice sine!!
notice it's 60Hz too.

[EasyGoing1]

Re: Kind of a different question...

wow - that's a nice sine!!
notice it's 60Hz too.

Yeah once I put a little force on the probe, the wave went from something noisy to that beauty right there ...

But what this is telling me, is that I have AC running through my laptop ... I'm not sure what to think about that ...

[stj]

Re: Kind of a different question...

what confuses me is that psu's usually couple the output negative to the rectified side of the input.
so you shouldnt see a 60Hz wave.
at worst you should see a 100Hz rectified sine with lots of dampening from the primary cap!

[eccerr0r]

Re: Kind of a different question...

Really doesn't matter if it's AC or not, just matters how much absolute current can pass through. Ideally that capacitor is small enough (in capacitance) that no more than 1mA will pass through or so, with any "proper" AC voltage presented at the input.

If you plug it into a GFCI outlet, short the case of the laptop to ground, and it trips, then you know you have a problem...

[EasyGoing1]

Re: Kind of a different question...

what confuses me is that psu's usually couple the output negative to the rectified side of the input.
so you shouldnt see a 60Hz wave.
at worst you should see a 100Hz rectified sine with lots of dampening from the primary cap!

Apple Sauce?

[EasyGoing1]

Re: Kind of a different question...

Really doesn't matter if it's AC or not, just matters how much absolute current can pass through. Ideally that capacitor is small enough (in capacitance) that no more than 1mA will pass through or so, with any "proper" AC voltage presented at the input.

If you plug it into a GFCI outlet, short the case of the laptop to ground, and it trips, then you know you have a problem...

Is there ANY risk of damage to the laptop doing that?

[TechGeek]

Re: Kind of a different question...

Is there ANY risk of damage to the laptop doing that?

Nope, you're just taking the stray voltage and sending it where it should've been in the first place.

[Per Hansson]

Re: Kind of a different question...

Well it's normal to see a 50Hz or 60Hz backgroud due to the house wiring.
Just so you don't confuse yourself you might want to watch this video.
https://www.youtube.com/watch?v=yKb7xIsPjVM

The filter that stj mentions is present in all hand held meters.
But a scope will not have it, and this picks this noise up, same for a high-end bench dmm.

[EasyGoing1]

Re: Kind of a different question...

Well it's normal to see a 50Hz or 60Hz backgroud due to the house wiring.
Just so you don't confuse yourself you might want to watch this video.
https://www.youtube.com/watch?v=yKb7xIsPjVM

The filter that stj mentions is present in all hand held meters.
But a scope will not have it, and this picks this noise up, same for a high-end bench dmm.

Thank you for that video. It makes perfect sense. But I'm not sure how this phenomenon applies to my readings when I have the meter on current reading vs. voltage reading. As we saw, the voltage reading was consistent between the Fluke meter and the oscilloscope ... and I can't take a current reading with the scope to demonstrate that the ZERO reading I was getting from the Fluke was due to the fact that it averages the reading over one power cycle...

However, I suppose it stands to reason, that where there is voltage, there has to be current ... and where the Fluke reads 6 volts yet 0 amps even at the microamp level ... I suppose this explanation is as good as any ... the other explanation could be that the actual amperage is less than one microamp.

[EasyGoing1]

Re: Kind of a different question...

An update on the original topic here ... I purchased this power cord for my MBP power brick and it has a spring-loaded flat piece of metal that grabs onto the metal disc that protrudes from the charger and I verified that the metal is connected to the ground pin on the plug. When I connected it to my charger and plugged it in, the vibration that I was getting from the chassis is now gone ... so it appears that the only way to properly ground a mac book charger is by purchasing one of these cables.

[kaboom]

Re: Kind of a different question...

When I connected it to my charger and plugged it in, the vibration that I was getting from the chassis is now gone ... so it appears that the only way to properly ground a mac book charger is by purchasing one of these cables.

Yes, you're returning the Y-cap leakage thru the EGC; the case (and V-) are now at GND potential. Or thru a resistor of 10-1000 ohms.
Measure the resistance from the case to the line plug's ground pin with a DMM!

[stj]

Re: Kind of a different question...

i find it interesting that some chinese company has to correct apples mistakes!

[akc1956]

Re: Kind of a different question...

Mine has the the contacts in the plug and they have continuity to plug earth pin. It is a A1466 macbook air, early 2015

[stj]

Re: Kind of a different question...

that may have earth continuity,
but all the apple chargers i'v seen for the u.s. only have 2 pins.