Reclaiming missing motherboard header

GuitarMan

New Member
I have a Dell Optiplex 3050 SFF (small form factor) PC. That SFF qualifier is not just a marketing term; things are pretty cramped inside.

Somehow, marketing often prevails over the folks who actually know what they are talking about in R&D, and this box is a good example.

It's not a state-of-the-art box, but when it came onto the market it had a pretty good feature set for its size:

It can run an i7-7700 3.6 GHz CPU
It can use 32 GB of RAM
It has a full-sized 3.5" bay for whatever drive you want to throw in there
It has a UEFI BIOS
It has an m.2 port, into which you can plug a drive terrabytes large, and it will use that, although technically it was meant for Optane memory
It has 4 USB 3.0 ports
It has an SD card reader
It can use a 240 watt PSU

What it does NOT have is enough cooling.

There are two very odd details about this machine, both of which relate to cooling.

There is a set of mounting holes right behind the front bezel (which is generously perforated), into which a Dell fan from other SFF models fits perfectly,

AND

There is a set of 4 solder points on the motherboard with the printing "FAN_SYS". The pads are lined up, but there is no header (plastic rectangle), and there are no pins.

Now if that's not an opportunity/disaster waiting to happen, I don't know what is.

I know the fan fits because I got one and installed it. The fan has a plug on the wires that would fit into a header.

I have a header of the correct size.

I can even harvest pins from a different board.

What I need is

1) to know if there is actually any juice available at those solder points, and

2) helpful hints on attaching the header frame and pins without destroying the board.

Pics:
Generously perforated bezel
Packed interior
Mounted fan
Solder points missing header and pins
What I want it to look like
 

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As it's a four pin header, it could have a permanent 12V supply & ground on two pins?

Looking at the the four pads as in the photo, the top should be 0V and the second one +12V.
Third is speed sense, lowest PWM for four-pin fan.

A three pin one will also fit, omitting the PWM signal.

If there is power there, a fan should work. A four pin needs a PWM signal so that is more dependant on the hardware - though it's possible the +12 is also PWM controlled and relies on the components being fitted.

If there is no power there, you could use an adapter cable from a four pin drive power connector to run a fan.
 
The other question is, does the BIOS know about that header at all. That is, will the hardware actually run the fan if you manage to get it connected. They may have stripped out some hardware code in the BIOS, but that may or may not be true, hard to say for sure.
If that box was designed for high power processors, then the BIOS will likely support the PWM header, you just need to get it connected. Using small wire-wrap wire to tack onto those header pin holes may work, at least to test if the fan runs properly, before you try to desolder/solder headers onto the board.
 
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