Psu Leaks Little Bit Of Ac To Gnd Pin, Normal?
- Thread starter urjaman
- Start date
mali
-
^ 
I thought it was urjaman's GF
I thought it was urjaman's GF 
I just checked my PSU and I can confirm this. I measured 85.9 V AC between DC ground and AC neutral (and earth ground).
Also there is a very noticable hum when connecting the Pandora with its audio output to my stereo while the AC adaptor is being connected.
This seems to be a very low quality AC adaptor. <_<
Also there is a very noticable hum when connecting the Pandora with its audio output to my stereo while the AC adaptor is being connected.
This seems to be a very low quality AC adaptor. <_<
Heh - that's what you get if you buy AC Adaptors NOT from China but from within Europe to make sure you don't need to CE test them... :/
Out of curiosity I've just tested several other similar PSUs of devices I had lying around, including some really cheap stuff from DX. None of them had any potential against neutral or ground at all (all of them showing exactly 0 V AC).
EDIT: I did a little more testing. I measured the voltage under some kind of load condition (a 1 kOhms resistor in parallel to the volt meter) and voltage dropped significantly (near zero). This means at least the risk for human is very little. In case the voltage had not dropped one would have expected a current of about 8.6 mA. Still these PSUs should be considered broken as it is not even legal in most countries to sell such power supply units (that are not grounded!) which are not galvanically separated from the power grid, which is obviously not the case here.
EDIT: I did a little more testing. I measured the voltage under some kind of load condition (a 1 kOhms resistor in parallel to the volt meter) and voltage dropped significantly (near zero). This means at least the risk for human is very little. In case the voltage had not dropped one would have expected a current of about 8.6 mA. Still these PSUs should be considered broken as it is not even legal in most countries to sell such power supply units (that are not grounded!) which are not galvanically separated from the power grid, which is obviously not the case here.
marshal
Member
wejp said:I just checked my PSU and I can confirm this. I measured 85.9 V AC between DC ground and AC neutral (and earth ground).
Also there is a very noticable hum when connecting the Pandora with its audio output to my stereo while the AC adaptor is being connected.
This seems to be a very low quality AC adaptor. <_<
All the bashing about cheap chinese power adapter and now this... can't help feel a bit disappointed.
Last edited by a moderator:
Prometheus
Well-Known Member
- Joined
- Mar 8, 2008
- Messages
- 9,472
craigix
Mega GP Mania
Can I assume the powerpax one is working fine? Maybe we should switch to powerpax for all the units.
The other one was supposed to meet all the standards too and was tested.
The other one was supposed to meet all the standards too and was tested.
Prometheus
Well-Known Member
- Joined
- Mar 8, 2008
- Messages
- 9,472
Craig, just a quick question while you're here, if I may ask: If you're switching to the other kind, will those of us with the one pictured in this thread be able to get an exchange?
MWeston
Internal Development
Just out of curiosity, what happens if you plug the Pandora power adapter in facing the other way? Is the AC voltage still present? I'm not really into this high voltage stuff but I remember a stove in an old rental suite I had was zapping me when I touched the fridge and stove at the same time. They were right next to each other which made it fun. I reversed the plug on the fridge and it didn't zap me anymore. It's one of those shitty things about non-polarized plugs that I learned about the hard way.
Although, these small switching supplies are supposed to use optical and/or transformer isolation to prevent this sort of thing so it might be different than two appliances that run directly off the 120V (or 240 in other countries).
Although, these small switching supplies are supposed to use optical and/or transformer isolation to prevent this sort of thing so it might be different than two appliances that run directly off the 120V (or 240 in other countries).
mali
-
^ I already suggested it above Same result.
Same result.
MWeston
Internal Development
I'm testing some AC adapters I have around my place to see what I get. Damn I hate working with AC, but here goes...
Pandora adapter (not PAX one, don't have one): 49.5Vac (from DC GND to AC EARTH)
Pandora adapter (not PAX one, don't have one): 48.9Vac (from DC GND to AC NEUTRAL)
CUI Inc. DMS0500500-P5P-IC (supposed to be high quality): 71.9Vac (from DC GND to AC EARTH)
CUI Inc. DMS0500500-P5P-IC (supposed to be high quality): 72.4Vac (from DC GND to AC NEUTRAL)
CUI Inc. EMS060300-P5P-SZ: 48.5Vac (from DC GND to AC EARTH)
CUI Inc. EMS060300-P5P-SZ: 48.6Vac (from DC GND to AC NEUTRAL)
Power adapter from my Samsung Netbook: 0.00Vac (from DC GND to AC EARTH) THIS ADAPTER HAS THE THIRD PRONG TO EARTH
Power adapter from an Energizer battery charger: 6.11Vac (from DC GND to AC EARTH)
Power adapter from an Energizer battery charger: 6.15Vac (from DC GND to AC NEUTRAL)
Power adapter from a Western Digital USB drive: 44.0Vac (from DC GND to AC EARTH)
Power adapter from a Western Digital USB drive: 44.7Vac (from DC GND to AC NEUTRAL)
JET PSAA10R-050: 45.0Vac (from DC GND to AC EARTH)
JET PSAA10R-050: 44.9Vac (from DC GND to AC NEUTRAL)
It seems that any adapter without the earth pin will have some floating AC between DC ground and the AC ground. Weird.
Pandora adapter (not PAX one, don't have one): 49.5Vac (from DC GND to AC EARTH)
Pandora adapter (not PAX one, don't have one): 48.9Vac (from DC GND to AC NEUTRAL)
CUI Inc. DMS0500500-P5P-IC (supposed to be high quality): 71.9Vac (from DC GND to AC EARTH)
CUI Inc. DMS0500500-P5P-IC (supposed to be high quality): 72.4Vac (from DC GND to AC NEUTRAL)
CUI Inc. EMS060300-P5P-SZ: 48.5Vac (from DC GND to AC EARTH)
CUI Inc. EMS060300-P5P-SZ: 48.6Vac (from DC GND to AC NEUTRAL)
Power adapter from my Samsung Netbook: 0.00Vac (from DC GND to AC EARTH) THIS ADAPTER HAS THE THIRD PRONG TO EARTH
Power adapter from an Energizer battery charger: 6.11Vac (from DC GND to AC EARTH)
Power adapter from an Energizer battery charger: 6.15Vac (from DC GND to AC NEUTRAL)
Power adapter from a Western Digital USB drive: 44.0Vac (from DC GND to AC EARTH)
Power adapter from a Western Digital USB drive: 44.7Vac (from DC GND to AC NEUTRAL)
JET PSAA10R-050: 45.0Vac (from DC GND to AC EARTH)
JET PSAA10R-050: 44.9Vac (from DC GND to AC NEUTRAL)
It seems that any adapter without the earth pin will have some floating AC between DC ground and the AC ground. Weird.
fusion_power
Advanced Member
If you order high quality Adaptors like so often mentioned from the OP Team, you should get them. ^^" Manufacturer already infomed?EvilDragon said:
I think I keep my old switching Adaptor from EDs shop that I've used with my GP2X. I hope its 1000mAh are enough for the Pandora.
Last edited by a moderator:
MWeston said:
I'm a bit rusty (and UK based) - but all I believe is being described here (& in the thread) are switch-mode power supplies that do not have an earth connection - so the output is floating. This typical causes "touch voltage" of roughly 50% input AC - which I presume is around 120V for you (so is probably the 44V->70V adapters above). This is known to give a tingle sensation, but the current that can flow should be tiny and therefore not able to cause injury. This is quite common with modern switchmodes.
Last edited by a moderator:
tsh
Active Member
The voltage is irrelevant, at least when measured with a dmm. and what you are measuring is in spec, so safe.
As I mentioned before, I have also tested some other adaptors and none of them had AC between DC ground and AC ground, except the Pandora adaptor. I'm not saying there are no other PSUs which have this problem, but definitely not all those ungrounded PSUs are like that.MWeston said:
Last edited by a moderator:
mali
-
^ My tongue test results conform with this statement.
hobbyman II
Member
- Joined
- Sep 7, 2008
- Messages
- 487
@Mweston ... it's a power supply, afaik optical isolation would be no use since you could only transfere miniscule amounts of power, it will be a switch mode device with isolation or just a isolating transformer and rectifier
@silver .... yeah!, it's a non issue, a case of a little knowledge misunderstanding things, if you used a old style coil meter that voltage probably wouldn't show since the meter would have sunk it, digital meters often place next too no load on circuits (apart from probe lead resitance,capacitance etc), it would probably not have been measureable on a cheaper (coil) meter.
@ hysterical masses .... the energy in the float voltage is puny, it's no real* risk even if you use it in the bath (which you shouldn't do with any electrical device btw), if you have lights or a lamp with a touch dimmer, or touch switch, you will find that all that is between you and mains voltage is two resistors, see diagram (not mine) touch switch, theoreticaly, the voltage on the touch plate can rise to mains voltage, but the capacitance of the plate/wiring is so miniscule it's no problem, hell, if you take off a nylon shirt you can hear thousands of volts discharging, but it's no problem, people don't get incinerated every time they take off a shirt, voltage isn't the real danger, amperage is, and there's no amperage.
float voltage is normal in electrical circuits, similary, some power supplies are so basic they rise in voltage as the current demand drops, thats why cheap units with a selector switch on them often overdrive devices, or you find it runs a low power device rated at 6v perfectly fine on the 3v setting, and that is why you you should never use a unregulated power supply to charge a battery pack, the voltage will rise as the pack charges and it will end up being trickle charged at some stupid voltage that destroys the pack, (Pandora has a regulated and PERFECTLY SAFE power supply, and internal charge manager chip)
to summarise, nothing to see here, move along :rolleyes: (see main post heading....operative words...."a little bit")
*for values of real I personaly consider trivial, but then I think most of the world is a bunch of girly nancys anyway (barring Chuck norris..sir!)
@silver .... yeah!, it's a non issue, a case of a little knowledge misunderstanding things, if you used a old style coil meter that voltage probably wouldn't show since the meter would have sunk it, digital meters often place next too no load on circuits (apart from probe lead resitance,capacitance etc), it would probably not have been measureable on a cheaper (coil) meter.
@ hysterical masses .... the energy in the float voltage is puny, it's no real* risk even if you use it in the bath (which you shouldn't do with any electrical device btw), if you have lights or a lamp with a touch dimmer, or touch switch, you will find that all that is between you and mains voltage is two resistors, see diagram (not mine) touch switch, theoreticaly, the voltage on the touch plate can rise to mains voltage, but the capacitance of the plate/wiring is so miniscule it's no problem, hell, if you take off a nylon shirt you can hear thousands of volts discharging, but it's no problem, people don't get incinerated every time they take off a shirt, voltage isn't the real danger, amperage is, and there's no amperage.
float voltage is normal in electrical circuits, similary, some power supplies are so basic they rise in voltage as the current demand drops, thats why cheap units with a selector switch on them often overdrive devices, or you find it runs a low power device rated at 6v perfectly fine on the 3v setting, and that is why you you should never use a unregulated power supply to charge a battery pack, the voltage will rise as the pack charges and it will end up being trickle charged at some stupid voltage that destroys the pack, (Pandora has a regulated and PERFECTLY SAFE power supply, and internal charge manager chip)
to summarise, nothing to see here, move along :rolleyes: (see main post heading....operative words...."a little bit")
*for values of real I personaly consider trivial, but then I think most of the world is a bunch of girly nancys anyway
(barring Chuck norris..sir!)
mali
-
^ The only probable problem I see is the current flowing from the common ground to audio circuitry ground when touching the outer ring of the headset port. If there is no chance this will damage anything then it's fine. I'd choose a better power supply for future batches, though.
tsh
Active Member
Agree with Mali, audio is the only feature where this could present any problems, and I think we might have realised if it was a general problem. For audio, earth loop breakers are often needed, and there is no guarantee that an earthen supply would improve matters. 1v at 50mA would upset an amp, but you won't feel it.
