Modify an HP Z400 PSU

[delingren]

I have an HP Z400 workstation with a busted motherboard. It's a decent case and PSU so I figured I'd modify it to house a standard ATX or mATX motherboard. Here is the question I have re. the PSU, which is a non-standard PSU. There 2 major modifications I need to do:

1. Change the pinout of the main power connector. Pins 12 and 23 on Z400 are both +12v as opposed to 3.3v and 5v respectively on standard ATX. Pin 20 on Z400 is ground but -5v on ATX. But no modern motherboard uses -5v anyway. I'm going to get an extension cable and rewire pins 12 and 23.

2. The CPU connector on Z400 is 4 pin. Most modern motherboards have a 8 pin connector. I'm going to get a 4 pin to 8 pin adaptor.

So, my two questions:

1. for 3.3v and 5v, should I just rewire to the main connector or should I use the SATA power connector? I suspect there is just one rail for each of them, right? So it doesn't matter as long as the wire is able to handle the current. It'd be safer to use an SATA connector but it's a little more work.

2. for the 12v on the CPU connector, is it better to use the now freed pins 12 and 23 on the main connector? Are they on a different rail than the original 4 pin CPU connector? If not, then I guess there is no point, except less current on the wires.

Thanks!

 

[Tom Keenan]

I'm terrible at electrical engineering, but to me that looks like a recipe to short out every single thing in your computer.

 

[nukemaster]

Seeing as the power supply is older, I would be interested in the power supplies label.

Older power supplies had more of the power dedicated to the 3.3 and 5 volt rails. Modern ones have more power on the 12 volt rail(and get the lower rails with DC-DC converters to keep efficiency high while allow enough 5 and 3.3 volt current for systems that need a bit more).

Re-wiring a power supply can work, but it would have to be a pretty damn good one to do that.

 

[delingren]

Though a little old, it was a workstation. The 12V output is 456W, which isn't too bad. I'm going to use an i7 4770 or 4790 and reuse one of the spare video cards laying around. I never do anything GPU intensive tasks. The most GPU hungry thing is some light video editing with Premiere.

Seeing as the power supply is older, I would be interested in the power supplies label.

Older power supplies had more of the power dedicated to the 3.3 and 5 volt rails. Modern ones have more power on the 12 volt rail(and get the lower rails with DC-DC converters to keep efficiency high while allow enough 5 and 3.3 volt current for systems that need a bit more).

Re-wiring a power supply can work, but it would have to be a pretty damn good one to do that.

 

[nukemaster]

For the rating is is quite good.

As long as you are 100% sure about what each wire does, I see not reason you can not re-wire it. Get what you need from the main ATX connector if you can.

While most boards have 8-pin cpu power connectors, many will work with the standard 4 pin(so you may not have to mod anything). My old i5 750 may take as much power as your new cpu and only uses a single 4 pin(that is all the board and power supply have).

 

[delingren]

Thanks! I looked up and you are right, the 4-pin CPU connector can power up to 155W, which should be more than enough.