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Heatsink Fuzz

This appeared while harvesting heatsinks and suchlike from a defunct Dell Optiplex:

Clogged CPU heatsink
Clogged CPU heatsink

The only way to get access to that end of the heatsink is to break the heatsink’s thermal bond to the CPU, which seems like a Bad Idea if you intend to continue using the thing:

Clogged CPU heatsink - fan
Clogged CPU heatsink – fan

I buy off-lease Optiplexes from Dell Financial Services (a.k.a. Dell Refurbished) and, although their interiors always look well-cleaned, Dell (or, nowadays, FedEx Reverse Logistics) may have decided against breaking the CPU’s thermal bond and just sent me an office’s dust collection.

Doesn’t look like my dust. That’s my story and I’m sticking with it.

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  1. #1 by Olli on 2019-03-09 - 09:45

    Blowin’ the Dust Away…

    “Using a leaf blower to blow out a dusty PC (again!)”

    • #2 by Ed on 2019-03-09 - 10:44

      Never flip up the green fan duct, lest you release the horrors below!

    • #3 by Jason Doege on 2019-03-11 - 09:42

      I wonder if you could accidentally spin a fan hard enough to power it up.

      • #4 by Ed on 2019-03-11 - 11:48

        For “ordinary” CPU fans, I think the (spinning) stator magnets won’t (don’t? can’t?) generate any winding current, because the stator MOSFETs are turned off when the supply is off. They certainly generate an AC voltage in the windings, but that won’t provide power to the controller.

        If you spin ’em fast enough, I’m sure the induced voltage could exceed the MOSFET body / flyback diode breakdown voltage, which can’t possibly be a Good Thing.

  2. #5 by Vedran on 2019-03-11 - 13:53

    Air had to get inside that heatsink to deposit all the dust, so strategically aimed air compressor nozzle would get it reasonably clean without disassembly. I do it with my laptops from time to time. Just keep the blasts short to avoid killing the bearings in the fan.

    • #6 by Ed on 2019-03-12 - 09:15

      The gotcha is being unable to get the air nozzle into the right position, because there’s no clear path into the heatsink outlet amid all the clutter over the system board. Blowing all the fuzz back through the fan seems fraught with peril, too.

      When I decommission the next carcass, I’ll haul it onto the patio, see how much fuzz it hides, reassemble it, blow it out, then take another look inside. For Science!

  3. #7 by eriklscott on 2019-03-12 - 17:55

    Removing and re-installing heat sinks isn’t a big deal. Clean with 90+% isopropanol, let air dry, and use a very small smear of thermal compound. Probably less thermal compound than you’re thinking. And then maybe a tad less than that. It’s not Magic Cooling Gunk, it’s just a gap filler.

    This level of detail provided for those who may stumble into this. I’m sure you’ve done this before, Ed. :-)

    • #8 by Ed on 2019-03-13 - 10:44

      Aye, and always with too much goop!

      It’s no big deal, but expecting owners (or even reconditioning techs) to get it right every time in an uninspectable area may be expecting entirely too much.

      In fact, I’d expect a business to ignore the fuzz until it’s time to refresh the machines for other reasons; those Windows 7 licenses ain’t gonna last forever, y’know.