Really simple, basic question about power supplies
- Thread starter mikepark
- Start date
Is common/ground (black wires) connected to the psu case? - Yes
So getting 3.3v, 5v & 12v from the red, orange & yellow wires to the case as well as black wires is the expected result? I don't understand
'getting wires to the case' and 'expected result'.
So getting 3.3v, 5v & 12v from the red, orange & yellow wires to the case as well as black wires is the expected result? I don't understand
'getting wires to the case' and 'expected result'.
nismoguy82
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- Feb 25, 2014
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Yes, all of those wire colors and voltages are apart of PSU's, as well as other wire colors for various things. Why are you asking?
nismoguy82
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I think he's Korean, looking at his name anyways. Probably used a translator to post his question.
- Dec 31, 2007
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voltage between psu red wire and psu black wire is 3.3v, which is ATX standard.
voltage between psu red wire and psu case is 3.3v, which would be expected if ground (black) wire connects to case.
Same thing for (using JCLO's notation)
black + yellow = +12vdc
case + yellow = +12vdc
black + blue = -12vdc
case + blue = -12vdc
black + orange = +5vdc
case + orange = +5vdc
So if I got all those measurements, does it mean the psu is performing as expected? Is there anything else I should test?
My SATA data cables are melting. Have replaced motherboard and tried with 4 different SATA devices. Same result. Measured voltages at SATA power cable and they are according to spec. What's left besides psu? This problem is driving me crazy.
- Dec 31, 2007
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No. It is 12.37v. The other voltages are 3.33 and 4.98, Could that be causing the problem?
BTW, it is the wires to pins #1 & #7 (ground) on the SATA data cable that are melting. The wire for pin #4 (3rd ground connection) may be melting but I can't see it because it is surrounded by more material. Pin #4 on the SATA device (but not pins 1 or 7) also shows damage. In fact, it is completely gone an a new 840 EVO SSD (sigh).
I looked up the ATX Specifications (v 2.2) and according to that, I should be OK. I think v2.2 is about 10 years old, but as far as I know, still applies. Of course, life doesn't always follow specs, so if there is something about that 12.37 v I need to know, I would very much like to know it. Here's the specs:
12v +/- 5% = 11.4v to 12.60v (Yellow)
5v +/- 5% = 4.75v to 5.25v (Red)
3.3v +/- 5% = 3.14v to 3.47 (Orange)
-12v +/- 10% = -10.80v to -13.20v (Blue)
Since it seems like a significantly different question, I started another thread asking if that SSD might work with pin #4 missing since there are 2 other grounds. I don't know what the internal circuitry of the SSD is.
Sort of.
The PSU provides full galvanic isolation between the AC mains and DC output, there's no conductive path between the primary side of the PSU and the secondary side of the PSU. However, the PSU's DC output reference is connected to the AC power system's earth ground which eventually does meet up with the AC neutral at some point down the line.
Ergo, barring physical modification of the PSU (not recommended), the DC reference should be pegged to earth ground, which makes the DC supplies (-12v, 3.3v, 5v, 12v) all relative to earth ground. Over the short haul there can be a small bias between the earth ground and AC neutral.
EDIT: the PSU case is connected to earth ground for obvious safety reasons. This makes it a part of the DC ground plane and equipotential to the black wires
- Dec 31, 2007
- 36
- 0
- 18,540
By
“Is common/ground (black wires) connected to the psu case?” I meant
“are the black wires from the psu connected to the psu case? Or to use Pinhedd’s words,
“is the PSU's DC output reference connected to the AC power system's earth ground”?
And if that is true, then
“getting 3.3v, 5v & 12v
from the red, orange & yellow wires
to the case
as well as black wires
is [would be] the expected result.”
By
getting a certain voltage from a particular wire to the case, I meant
getting a certain voltage between a particular wire and the case.
I submit that “getting wires to the case” is a misread of “getting 3.3v, 5v & 12v from the red, orange & yellow wires to the case”. The sentence describes getting a certain voltage from a particular wire to the case, not getting a wire to the case. The difference is significant.
This is a side thread to a couple of other threads in which I was probably too detailed, so I was trying to be as terse as possible. It seemed consistent with a lot of what I read here and I thought getting a voltage from something to something was an acceptable way of saying getting a voltage between something and something.
I am (in equal proportions) Scotch, Irish, English and Welch and have lived in North America since before the Japanese bombed Pearl Harbor (except for a few years in Europe and Southeast Asia). I do get a fair amount of junk mail in what I presume is Korean, but I don’t speak a word of it, so I don’t know.
I usually refrain from being defensive in forums, but you hit a beloved patriot in my armor. I consider myself far more accomplished in the use of our beautiful language than I am at computer technology and most of the people I know consider me a source of expertise in that arena.
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