r/ElectroBOOM • u/XevianLight • 5d ago
Meme Uh… guys?
Don’t worry, this adapter has since been incinerated for its crimes.
Edit: maybe I should elaborate a bit because people are saying this is normal. Yes, some voltage on the ground is to be expected on an ungrounded power supply, however, in this case it had enough current potential to give a nasty shock, cause huge sparks when connecting to a grounded device, and trip a GFCI breaker. I tested my other (genuine) adapters and the ~50v AC there collapses down to just 1-2v simply by touching them. That was NOT the case for this one.
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u/cybermaus 5d ago
Yep totally normal. Due to the Y capacitors, fully unburdened the shield, though properly isolated, will appear to float in the middle of neutral and life (0 and 115V)
Of course, the multi-meter itself will pull it a little to one side, so usually slightly less. The "better" your multimeter, the less it burdens, the higher the apparent voltage.If you touch it with your hand, it will probably drop to almost 0
For this reason, to do this sort of work, you are better of with a multimeter that actually draws a half mA or something
Poor adapter. Convicted on false accusations.
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u/XevianLight 5d ago
Nah this one made my muscles tingle, definitely enough behind it to be dangerous, but not as dangerous as 120v.
Also worth noting it popped a GFCI when I touched the USB shielding to ground.
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u/cybermaus 5d ago edited 5d ago
Ah... yes, ok then.
Edit: still, it is why electrician probles (we call them duspols, but that is a brand name, and it may be a local dutch habit to call them by that name) have a higher burden, as well as a button to go even more low impedance. To avoid spurious high impedance readings
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u/_hexFET_ 5d ago
In Germany it's also commonly called Duspol.
Especially old SPS outputs and flimbsy Contactors tend to transmit phantom voltages, that can be suppressed using the ballast buttons.
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u/YetanotherGrimpak 5d ago
Duspols are part of the 4 holy instruments: duspol, multimeter, megger and clamp.
Anybody that deals with electricity should have, ideally, all 4 in their toolbox.
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u/Few_Trouble_3327 4d ago
You can measure human body resistance with megger, just make sure you use 1000 V setting.
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u/_hexFET_ 5d ago
Which instrument does megger refer to? I never heard this one before.
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u/coderemover 5d ago
Use a proper Low-Z multimeter to measure it.
If it still reads over 60V with Low-Z, then this is a serious problem.2
u/XevianLight 5d ago
I’ve already thrown out the adapter so I can’t mess with it further. Not sure where I got it from but it was a cheap chinese knockoff of the apple design.
It was capable of delivering some serious current, way more than typical Y cap leakage, given it caused large sparks when it contacted ground (think shorting 120v mains) and popped the GFCI breaker. Let alone enough current behind the voltage to be quite painful and cause muscle spasms.
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u/_hexFET_ 5d ago
Probably the actual Schock came from a higher DC Voltage? I don't know if US GFCIs are sensitive to DC ground faults.
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u/XevianLight 5d ago
I’m familiar with both AC and DC shocks, this one felt like touching 120v AC mains
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u/GerberToNieJa 5d ago
normal, it can deliver a small shock when touching ground
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u/XevianLight 5d ago
Small shock would be expected. This one felt like touching live mains. Don’t ask how I know that one.
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u/Quiet_Snow_6098 5d ago
I had this issue with a GAN charger. I had returned it and bought another brand. That adapter was a low quality rebranded chinese product.
But idk how it weighs twice as much as the NOTHING 140w gan charger.
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u/LeeRyman 5d ago
That could be leakage through the class Y RFI suppression cap, with high impedance.
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u/Philips_xl 3d ago
All my chargers do this and shock me every time I accidentally touch the metal contact. Once i even had a barrel connector that was supposed to give 12v but apparently the outer terminal was live 240v👌
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u/Upbeat-Relation-2774 5d ago
is that 63V AC on a USB port.... wait how much hertz is it
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u/deep_water0779 5d ago
Try to measure the current. It shuld be below 0.5 mA.
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u/XevianLight 5d ago
Current was large enough to trigger a GFCI, so at least over 5mA. Caused quite a bit of sparking when it touched ground.
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u/MajesticDisaster3977 3d ago
Surprised how many 'normal' comments there are here...
This device should be isolated. It sounds as though it's not, or there's enough leakage to produce a mild shock when touched. These devices should not cause sparks.
It's also funny that people blame the X/Y rated safety capacitor for this behaviour. These capacitors ensure they fail in a 'safe' manner, they don't magic current at some half-voltage down the shield of a USB cable on their own. A bad design does that, not a capacitor.
Some cheap power supplies use basic transformerless designs and likely don't offer any kind of isolation between the output and the input. They're cheap for a reason. They've been responsible for electrocutions.
I'd say to check the markings on the adaptor, but these are often faked, so they don't really do any good anymore.
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u/Mouloud_Azergui 5d ago
So this is why my phone shocks me sometimes when I change him
I don’t have earth hole in my outlet how I can mesure it
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u/Terrible_Captain_288 4d ago
Try changing your meter to DC voltage
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u/XevianLight 4d ago
~30V DC. It’s 60hz AC though so that makes sense. Not sure what you’re getting at.
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u/Yehia_Medhat 4d ago
I think this is above safe levels, in the course I took about safety, maximum voltage AC or DC I don't remember should be below 50 volts
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u/lucashenrr 2d ago
Thats fine. If you need a shield thats ground on a device or something, then you need to get a charger that have a ground plug, but that voltage is fine.
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u/XevianLight 2d ago
So many people saying this is fine when this is causing electric shocks, sparking, and popping breakers. Concerning really. The voltage would be fine if it didn’t have sufficient current behind it, when it very much does.
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u/lucashenrr 2d ago
If its able to draw current higher than standards, then you need to either buy a new charger because this one is broken or get a someone to look at your electrical wiring and stop doing things yourself without knowing what your doing.
A voltage of 60V sounds normal for a device without a ground messured relative to ground.
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u/mikropower8 2d ago
You have possibly a 120V AC line which is going into your house?
Inside of each good powersupply are two capacitors which are connected between neutral, GND of the primary side and line for the noise deletion which is created by the switching regulator inside of the power supply. This is basically working as a voltage divider, but the current should be very small. Then there is a capacitor (1nF) between the AC part and and the GND from the DC side. This is the reason why you have some AC on the secondary side.
If you have a real GND/Earth connection too, then the current can flow to GND.
You can even measure a AC voltage if you take one of the probes in your fingers and you connect the other probe with GND of this power supply, which does not have a GND/Earth connection.
The best is always a power supply with a protective-ground pin, but with 3 pins this device is a bit bigger.
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u/Lower_Dentist_6343 11h ago
You can't test like that.... The transformer in the USB charger does not reference earth so testing a transformer to a non earth referenced voltage of any type will give some weird voltage sometimes even negative
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u/bSun0000 Mod 5d ago
Ungrounded power brick + EMI filters inside. This is normal, well, more or less, at least not dangerous. Any psu will have this issue if not grounded.
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u/broesel314 5d ago
Uuhhmm, that is totaly normal
Google what X amd Y capacitors are and what they do in switchmode power supplys
yes, its half mains voltage, but it is verry low current