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Posted at 6/18/2017 08:06:38
Last edited by korinel In 6/18/2017 08:41 Editor
Update:
I produced a copy of the top of the case using a sheet of perspex, cut with a scroll saw. In addition, I added a circular port and 4 small screw holes to that I could mount a small 40mm fan to the underside of the top perspex sheet using M3 screws, making sure that it was positioned just a little above the heat sink. The fan in question is a Scythe Mini KAZE 40mm Silent Case Fan (SY124010L), which costs about $9 at Amazon in the US. As per previous trials, I used HandBrakeCLI to transcode an MPEG-2 TS video to MPEG-4 AVC (h.264), which uses every CPU core intensively.
+0 min: Temperatures started to climb rapidly from starting temperatures of 42 C (zone 0) and 40C (zone 1). The CPUs were operating nominally at 1.99 GHz (A72) and 1.50 GHz (A53)
+3 min: Temperatures have climbed to 64 C (zone 0) and 54 C (zone 1), and CPUs continue to operate at nominal temperatures.
+10 min: Zone 0 now peak at ~68 C, with processors still functioning at maximum frequency. Zone 1 temperature continued to climb, eventually stabilizing at around 57 C. No performance impact.
+15 min: Zone 0 now peaks around 68-69 C, and zone 1 at 57-58 C. Still no processor throttling or performance impact. After this point, no further temperature increases were experienced.
Conclusion: Positioning a fan above the heat sink, even a small, quiet one, makes all the difference. For those that are happy cutting their own materials, I recommend it. Positioning the fan as close as possible to the heat sink makes a large difference. Just an extra 15 mm above where I settled on reduced the effectiveness to almost zero.
Additional: The fan is actually rated at up to 12 V, but I was using it at 5 V due to the even-more-silent operation. However, I discovered that at 5 V it often struggles to spin up after a power cut, however, sometimes requiring a nudge. Switching it to 12 V made it a little louder, but still very quiet, and the cooling performance improved massively, peaking around 54 C and 45 C. Also, after conducting the initial test I lowered the fan even closer to the heat sink, which further improved cooling performance. The 12 V to 5 V trick to get 7 V might also be worth trying out for an intermediate noise level. In any case, this fan is pretty awesome for its size, and WAY quieter than the stock cooler which whines unpleasantly.
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