I'm trying to use an old 20 pin ATX power supply as a substitute for the failed power supply in a Dell Optiplex 7040† I managed to find the pinouts for the Dell power supply which only has two output connectors. One of them is a standard 4 pin CPU connector. The other one is a non-standard 8 pin connector. I compared the pinouts with the old 20 pin ATX, and everything matched: BLACK Gnd; GREEN PS_ON; GRAY PWR_OK except for the purple wire. Every pinout I found for the ATX power supply indicated PURPLE +5VSB. The problem is that the "Dell" pinout showed the purple standby wire as +12VSB.
My own uneducated guess tells me that the ATX standard would not allow anything other than the specified +5VSB The other factor which fed my suspicions was that the "Dell" pinout wasn't from an official source, but was posted by someone in a user forum and the diagram didn't have a professional appearance the way I would expect a diagram would look if Dell had made it. I think it's likely that a mistake was made transcribing the pinout I found posted in the forum. It was a long and frustrating time I spent before finding the "Dell" pinout, so I thought I would try asking here before searching for another pinout that agreed with the first one. (And if those two pinouts didn't agree, then this unpleasantness would continue at least until I found a third pinout to break the tie!)
I hope this question isn't excessively low in quality and/or particularly annoying to the reader, since I can imagine someone pointing out that the only way to get a reliable answer is to hunt down the actual documentation from the manufacturer. I really went nuts just to get the "Dell" pinout above so I'm willing to settle for a less than a definitive answer if it were something like, "I've been a professional in the field since the first IBM PC and, while I can't say I'm absolutely certain that no PC has ever had the purple standby wire carry +12VDC, I think you'll probably be OK assuming that it's really +5VSB" I'd even be OK with a 1 in 10 chance of disaster if the odds came from a seasoned pro who was comfortable in making such an estimate of nominal accuracy.
I hope I haven't made a faux pas by including the previous paragraph. In the event that it was a blunder, can I pivot to a less subjective question? Assuming that the pinout is true and +12VSB is actually correct, what are my options going forward? What functionality depends on the purple standby wire? Would my PC be inoperable without it? How critical are the tolerances involved? Is there any/enough flexibility in the design specifications to allow modification? Would it be possible to (gulp!) splice the purple wire to a 12V switch-mode "wall-wart" which came with my USB external hard drive (or any such typical 12VDC adapter)?
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† The old ATX is too large to fit in the PC enclosure, so I plan on using it as an external power supply and running the wires into the PC where they've been spliced onto the connector taken from the failed unit.
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EDIT: the original version of this question implied that I had verified WHITE +12V . . . But I learned from the answer I got that this color was used for a different voltage and not even used at all anymore. I didn't want to have bad information sitting there looking like it was true (even if it is just in this little question), so I edited it out of the question and added this acknowledgment of what I did so that the answer and comments don't appear to be making references to something that doesn't exist. Yes I know that I'm going overboard to preserve context when it's most likely that nobody would ever notice or (more to the point) even be reading this in the first place! Obsessive waste of time on my part, yes. Well... that's what I do!
