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I'm hoping to add USB 3.0 to the server blade that I picked up for personal use. However, it has no peripheral connectors (3.5" HDD power connector), only a motherboard connector (used), and some proprietary connectors (used), and several PCIe connectors (unused).

I know I can use the PCIe 12V and ground for the peripheral connector, but how can I power the 5V line?

I've thought of a couple ways that might work.

  • I could splice second wire into the motherboard Molex connector.
  • I could install a 12V to 5V DC-DC converter powered by one of the PCie power cables.

Are these dangerous or harmful to the machine? Are there other options?

Pertinent Details:

  • Dell Precision r5500 workstation (specs here)
  • 1100W Power Supply
  • PSU can supply 5V 32A (not all used by mobo and HDD's right?)
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You are correct. Not all 32A are used by the motherboard and hard drives. This is simply the MAX current it can supply. You should be able to look in your mother board manual to find how much it draws, and same with your hard drives. All the red and black wires on molex are 5 volt and yellow and black are 12 volt. You could definitely take power from an existing one. Just as a tip, if you do this, try using an old molex you can connect to the power supply one so you don't have to hack away at your power supply wires. Make sure to use proper connectors when joining wires.

  • Great tip! I'll pick up a motherboard connector extender and splice that. I was nervous about messing with the original wiring. – Echo Nov 11 '15 at 14:59
  • If the wiring goes bad you are out 50 cents as opposed to a new power supply :) Can you please mark this as an answer? Thanks – Eric F Nov 11 '15 at 15:00

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