PSA: Do not use an HP power supply.

[TomXP411]

From Discord today: @SlithyMatt had a problem with the audio on his CX16 motherboard. As in, he's not getting any sound. It turns out, the power supply in his HP case does not have a -12V rail, and so the audio op-amps do not work.

According to Kevin Williams:

The YM2151 only needs 5V, but the OPAmps use 24V. I could have used 5V for the audio circuit, I just didn't want to because I personally like the sound of more headroom.

Companies like HP and Dell may not include a -12v line on the power supplies in their branded computers. Since their machines are engineered to work with their branded OEM components, there's no need to actually be compliant with the ATX specification for power delivery. Basically, HP can use whatever power supply setup they like, even if that PSU would not work on another brand of PC.

I have seen similar issues with Dell, not to mention them using a different pinout than ATX while using the same connectors. So at this point, we're advising against using a power supply from HP, Dell, or Lenovo.

When purchasing a power supply, look at the specification sheet and confirm there is a -12V line.

As an aside, if you're planning on running your board "naked" while waiting for the official X16 case, you might look at these little "Pico PSU" power supplies.

https://www.amazon.com/RGEEK-24pin-Inpu ... B07WDG49S8
https://www.amazon.com/RGEEK-24pin-Inpu ... B07PPYWGNH

These are representative samples, picked because they actually show a spec sheet on the Amazon listing. Others may also work, but the important thing is that the power supply actually supplies -12v on pin 14 (or 12 on an older unit) , as seen here:

https://www.smpspowersupply.com/connectors-pinouts.html

[kelli217]

PSA: Power Supply Advisory

[Daedalus]

You shouldn't use power supplies from old HP computers? Yeah! You shouldn't use male to male extension cords either. Some things SHOULD fill you with feelings of horror and dread.

"Power Supply Advisory" Ok, that's not bad. A roommate of mine was taking an electrician class and on a test was asked what "GFI" meant. He didn't know, so he answered "Go For It!" He never mentioned that class again, I don't know why.

On topic, I like the combo deal with the 150 watt Pico supply... you get the supply, the power brick and a sweet ITX case that works with them for a shave over a C-note. Future me will like it when the ITX sized X16 comes out!

[StephenHorn]

I don't see how it's immediately obvious that we shouldn't use the power supplies from OEM PCs. Is that a thing that kids just know these days? Am I a Joey?

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