I will test before I move them to water and share if it improves... for now 650Mhz @ 2.6T for 48hr and heat is well managed by the current design just with the few mods I did. Since the new 1397AI chips I ordered have not arrived yet for repairs I will stay away from 650+ speeds as I need these for testing.
That sounds great! I will try rotating the fan, too then.
For what it's worth, my experiment with a loosely positioned 'exhaust fan' did not last long; 8h in, the hashrate dropped to 2.4Th/s again. I'm not sure why, but my chips perform well, for a few hours and then slowly drop further and further. It must be thermally related.
add thermal pads to the bottom heatsinks 1mm @ 13+w/k will have the highest impact in it, those few changes will give you
650@2.5-2.6T stable on a ~120W on stock voltage.
Just to be clear: the bottom heatsinks just cool the PCB? And by default are bolted on without any thermal interface (pads or anything else)?
I'd like to prevent touching the top heatsinks, since I believe there's a chance to rip a thermal pad if you don't screw the heatsink on perfectly straight, which would then connect grounds and lead to magic smoke.
But bottom heatsinks are a mod I may actually do. I even have 12W/mK 1mm pads here.
the pcb is taking the back heat from the asics, they come with no thermal interface on them, only air therefore the heat stays and gets into the pcb/components including asics.
what i usually do is change both up and lower but upper vs what you have are better 20w/k once you lose the bolts the bottom will fall, do 1 at time just be careful of not move them much.
overall that will help the Asics to get cooler same PCB as also power controllers getting hot will lose capacity and cause performance issues, so keeping all as cool as possible pays out in higher room to push hard the asics and stability of other components.
hope makes sense to you.