Toward the end of this
thread, there's some photos showing the detailed construction of my hi-Z equal-airflow test jig based on the SI-128SE. Bright and early this morning, I fired it up. It crashed and burned on the runway (old aviation expression referring to really bad aircraft designs).
edit: see added comment at the end of this post, and changed subject.
Applying 12.7V to the Noctua fan, the airflow sensor prop barely rotated at all with the 9-blade Noctua turning 1401RPM! I looked for the obstruction I had overlooked. Nada. The jig, in this example, is
the SI-128SE's cooling-fin block and the fan mounted directly on it. I took it apart anyway and confirmed that there was no unexpected impediment, just the closely spaced fins.
Substituted a Slipstream800. At 12.7V, not enough air came out of the rear of the cooling block to move the sensor prop at all.
So, I used my Mk I airflow sensor - my right hand - to try to make sense of what was happening. There was
airflow out the back of the cooling block. Very little airflow. At the front of the fan, my hand detected a lot of swirling air (due to the rotating fan blades), but this masked the little movement of air into the fan (and thru the cooling-fin block).
The SE-128SE has a buncha little holes in the fins that the original SE-128 didn't. My hand/fingers could detect air coming out of these little holes, and in fact from every tiny gap etc. But not much, and not much at all from the back of the fin stack. Boy, I hope nobody is counting on all that super VRM cooling from the downflow air out of an SI-128SE!
I chose the 128SE as the basis for my Hi-Z fixture because I thought it would be, well, Hi-Z! A pretty good brick wall was not what I was expecting.
Two planned Z fixtures to go: a Mid-Z based on the S-1283 HSF's cooling-fin block, and another using fan adaptors with different input areas to simulate exhaust fan air impedances. I'm pretty sure the last one will work as expected; there's a whole lot of fan adaptors and if the airflow was blocked I'm sure we would all know about it by now!
You can do a crude version of this test non-destructively on your 128SE, or TRUE, or any HSF with closely spaced fins. Just pick up the HSF, mount a fan, connect the fan to 12V, and see how much air flows out of the other side of the cooling-fin block! No computer (or CPU, or mounting) needed as long as you can get 12V someplace.
edit: This design attempt was not
a total fiasco. I simply failed to use adequately high-pressure fans. There's lotsa 2000RPM fans around, and they would work great on this HS and test fixture. But those fans are noisy, and are of no interest to me - and I'm running this particular show.
Later the same day, I discovered the identical, unmodified fixture base works fine with ~1200RPM fans (or maybe less) using the HDT-S1283 HS, which has slightly wider fin spacing.