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Technical Q: should a PSU's ground output be floating?

X

xorbe

Supreme [H]ardness
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Sep 26, 2008
Messages
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I have found that my old PSU's ground seems to be floating -- ie, not connected to ground at the wall. My new SeaSonic S12II-520W seems to wire its ground output to the wall's ground/common. I found this out by getting shocked when attempting to connect the line-in from my stereo to the new HTPC I am building.

(Seems like there's something wrong with my stereo -- it measures 50.0V A/C between its line-in wires and ground at the wall. Enough to cause extended tingling in the hands afterward -- dangerous.)

Anyways, should a computer PSU have a floating ground, or can it be tied to grid ground? (My intuition tells me it should be floating, but surely it must be spec'd out somewhere.)
 
You should not be getting 50v from your stereo line out in the first place. Are you sure it is AC not DC? The ground or outside pin should not be that high. All your equipment should related to one ground. You should not be feeling tingling in your hands with line outputs. Something is not right. Any outside cable connection to any of your equipment?
 
Every desktop PC PSU i've seen tied the DC earth to mains earth, i'm not sure if this is a requirement though or if it's just done because it's easier to comply with certain other rules (in particular on EMI) that way. Power bricks and similar small PSUs usually have floating outputs.

As for the stereo it's not unusual for there to be some voltage on a floating appliance relative to earth and sometimes it can give a small shock from charge built up on filter capacitances but if there is a sustained shock then there is something wrong with the appliance (most likely a filter capacitor has failed and become leaky).
 
Do you shock by touching the pc without the stereos wire in your hand?
what stereo is it? Does it have a outside antenna?
 
If your reading 50v between the ground and the neutral you got some bad wiring in your house. Or or you saying the stereo shocked you? if so that thing has some thing wrong whit it get it fixed or trash it.
 
thax said:
If your reading 50v between the ground and the neutral you got some bad wiring in your house. Or or you saying the stereo shocked you? if so that thing has some thing wrong whit it get it fixed or trash it.
Click to expand...

I think the OP meant hz or something a badly grounded PLANT reads about 20v. Ground loops are in the mili volts. But 50v! Lol

Anyways Op even most "perfect" two prong stuff will still show about 60V on the case so you must measure for current
 
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The house wiring is fine -- I checked that hot and neutral were on the correct spades, and that ground is connected properly. I'm probably barking up the wrong tree about the PSU ground output being tied to input ground or not.

Here's what I found: from any of the 3 wires of the stereo's RCA line-in inputs, there's 50V AC to ground/neutral. It's only 160 uA when shorted out. It disappears entirely if the old HTPC PSU is plugged into the wall even without anything else hooked up to the old HTPC. It disappears with the new HTPC plugged into the wall IF the HDMI cable to the TV is plugged into the PC. Which is odd, since the TV has no connection to the stereo.

Everything is connected to the same 6-outlet strip. There are no external connections (not even cable TV).

Sharp Aquos 52" led TV
Yamaha HTR-5250
powered sub
Oppo bluray player
computer

The tingling was between the computer case (ground) and the stereo's RCA line-in inputs. Everything works fine when connected. I understand AC inducts onto pairs of wires ... but it shouldn't be enough to tingle, I thought. I think it's the (freebie) stereo. I've got an old crap KLH stereo with a crackling (failing) output section, but I can test with it next weekend.

edit: if I plug an RCA from the TV to the stereo, then the voltage disappears ... I think the stereo has a grounding issue.
 
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One power source, no antenna ... I asked my electronics guru friend at work (who gave me the stereo a few years ago), and he said it sounds like something is failing in the amplifier/transformer section of the stereo, causing electrical leakage back to the input section.
 
I would get rid of that freebie stereo that seems to be causing the problem. Sooner rather than later... I'd hate to see it blow up something else connected to it. Or cause a shock, sparks, or fire.

You checked the house wiring, so that's good. And yeah, every PSU I've seen has come with a three prong grounded power cord.
 
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