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Thread: PBO Cooling Suggestion

  1. #1
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    Default PBO Cooling Suggestion

    I am another one with a noisy PBO and the replacement fan (shipped really fast... great service) is exactly the same. I am of the opinion that this is mostly a resonance issue rather than turbulence noise. The fan was virtually silent when connected and held in my hand. It is not until you mount it that you get the irritating whine. And by applying pressure to the fan bracket in different areas I can get the noise level to change. And picking up the assembled PBO from the table top changes the noise yet again. All evidence of resonance on the thin metal structure to me. I may try mounting it with double sided tape but haven't got around to it yet.

    But here is another idea for those that want to run their PBO fanless but are worried about thermal. The main device to protect is the media processor (the device with the heatsink). If you look at the back side of the board beneath this device you will see a square patch of copper (covered in solder). This is a printed circuit board method of drawing heat from the bottom of the device via thermal vias. Put your finger on that patch while the PBO is running and you will see what I mean. So I thought, why not help wick the heat away from that patch? So I grabbed a Zalman video card low profile memory heatsink (the blue ones) and stuck it on the patch. When reassembling the box the heatsink is just the right height to make contact with the aluminum enclosure as you slide it in. Now you are conducting heat away from the device not only by the heatsink but also through the thermal pad on the bottom. I wish there was a way to read the silicon temp of the device but I can guarantee it is running cooler. Just not sure how much cooler. At least it makes me feel a little better about running fanless. I do enjoy the silence

  2. #2
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    Default Is that the one you mean ..


  3. #3
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    Quote Originally Posted by aasoror View Post
    Yes. That package comes with 4 of the high profile and 4 of the low profile. I used 1 of the low profiles and it is just the right height.

  4. #4
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    Quote Originally Posted by Dadi_oh View Post
    Yes. That package comes with 4 of the high profile and 4 of the low profile. I used 1 of the low profiles and it is just the right height.
    Thanks for the confirmation, I will go ahead and get a pack.
    That said, I was under the impression that issue wasn't about the chip overheating (the Asus O!play has the same chipset yet its running fanless and in a plastic case), I thought it was about the excessive heat produced by running a HDD inside the PBO, in that case I don't know how can the extra heatsink make a noticeable change (unless you stick one ontop of the HDD as well) and run the PBO fanless with a HDD in there.

  5. #5
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    Quote Originally Posted by aasoror View Post
    Thanks for the confirmation, I will go ahead and get a pack.
    That said, I was under the impression that issue wasn't about the chip overheating (the Asus O!play has the same chipset yet its running fanless and in a plastic case), I thought it was about the excessive heat produced by running a HDD inside the PBO, in that case I don't know how can the extra heatsink make a noticeable change (unless you stick one ontop of the HDD as well) and run the PBO fanless with a HDD in there.
    2.5 inch hard drives are fairly tolerant of heat given the environments they see inside laptops. Most are rated to 55C ambient air temperature. They also don't have a particular point to attach a heatsink; they rely on the air temperature around them rather than point cooling of a specific device. Placing a heatsink on the top case of a hard drive probably does little to help the individual components of the drive itself (but it can't hurt I suppose).

    As far as the rest of the components on the PBO circuit board they are mostly power related or passive devices which can take much higher temps. The memory would also benefit slightly from a heatsink but most critical component is the media processor.

    I am also not convinced that the fan does a whole lot the way it is configured. Most cooling systems rely on drawing cooler air from outside of the enclosure and then exhausting the hot air after it has flowed over the components inside the case. They way they have the fan on this unit is seems to just blow air around inside of the box. The added air turbulence is useful for the heatsink to do its job (preventing dead air lamination around the heatsink) but I'm not sure it does a whole lot to get the resulting hot air out of the case.

    One of the things that this ram sink on the back will do is conduct some heat from the media processor chip directly into the aluminum enclosure and use that large surface area to radiate into the surrounding air. I'm not sure how much it helps though. I would have to attach a thermocouple to the device and measure the delta with and without the extra heatsink.

    Another alternative would be to replace the top heatsink with something larger. I may look through my collection and see if I have a low profile one that would do the job.

    Like I said, I'm not sure how much the back heatsink helps but it sure doesn't hurt particularly if you have extra sinks laying around and it is a free fix.

    Cheers

  6. #6
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    When I get a chance I think I will place a thermocouple on the case of my hard drive and then seal the enclosure. That will give me an idea of whether I am running the disk too hot.

  7. #7
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    Quote Originally Posted by Dadi_oh View Post
    When I get a chance I think I will place a thermocouple on the case of my hard drive and then seal the enclosure. That will give me an idea of whether I am running the disk too hot.
    Yesss .. please let us know the results ..
    by the way, you true about the meaningless air flow, there is a very neat air channeling solution here (poster also replaced the stock heatsinks).

    I too am not sure whats the purpose of the fan .. as you pointed HDDs are running practically fanless since the start of time in any laptop. The chipset are running fanless in lots of similar media players .. but since I know my box gets really (like hurting) hot before applying the channeling solution, I would have never dared running it fanless with an HDD in there.

    Keep us updated.

  8. #8
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    Quote Originally Posted by aasoror View Post
    Yesss .. please let us know the results ..
    by the way, you true about the meaningless air flow, there is a very neat air channeling solution here (poster also replaced the stock heatsinks).

    I too am not sure whats the purpose of the fan .. as you pointed HDDs are running practically fanless since the start of time in any laptop. The chipset are running fanless in lots of similar media players .. but since I know my box gets really (like hurting) hot before applying the channeling solution, I would have never dared running it fanless with an HDD in there.

    Keep us updated.
    The channeling looks like an excellent idea. That was my point. In the original configuration the fan just seemed to blow air around inside the box. A properly designed cooling system should bring cool air from outside of the enclosure and direct it over the devices to be cooled and then exhaust out of the box. The addition of the divider is trying to achieve that. I think I will give that a try. Thanks.

    I don't have thermocouples here with me; I need to borrow a couple from my lab at work. I do have a non-contact temperature probe but I wouldn't be able to "see" the internal components with the box closed so that doesn't help. I could measure the temp of the case right below where I mounted the backside heatsink and see how much hotter that is than the surrounding area. That would give some indication if the backside heatsink is conducting heat to the enclosure. Although the aluminum does do an excellent job of quickly dispersing that heat.

    I have a bit of time now so let's see what I can find out. So far it has been mostly conjecture on my part so time to see if the data fits.

  9. #9
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    Well here are the results of my "improvements" to the PBO cooling.

    First, here is the Zalman heatsink on the back of the media processor (there is a thermal pad connected by thermal vias to the topside). You can see the ambient temp of 20C by the measurement of the enclosure. The zalman is running at 46C which means it really is wicking heat away from the media processor. You can also see that it just fits inside the case. It barely touches so a future improvement might be thermal paste to ensure contact as it slides in.

    Also measured the disk and it is about 9C above ambient. A movie is being played off it so it is active.

    I removed the fan and put double sided foam tape around the perimeter of the hole. It not only seals it but provides a damping isolation to the metal case. I then measured and installed a baffle made of teh clear plastic case from some OCZ RAM. This plastic is ESD resistant I assume since they ship RAM in it I did leave a flap at the top to allow it to seal against the top of the enclosure when it is slid into place.
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    Last edited by Dadi_oh; 01-30-2010 at 11:37 PM. Reason: typo

  10. #10
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    Only 5 attachments per message I guess... Part 2.

    Attached fan with tape and installed baffle. Last step is to put additional isolation on the thin feet that come on the PBO. I grabbed some clear bumpers and put them right over the top of the existing feet.
    Attached Images Attached Images

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