The fan speed can easily be lowered safely by using the external fan control switch then a 200ohm resistor in line from the fan speed pin to the ground pin. I just used the resistors that come with the LED packs where they throw in those resistors for free.
It works just fine to bring it to just about the same as the lowest setting with the pot and since the only real reason that the fan spins so fast on those PSUs (or others) is that it is used to exhaust heat from the server. These supplies could probably run even without a fan as even with full load they barely heat up. If you open one of these you can see that the PSU PCB only takes up about 3/5 of the case so with all that extra space and all that metal housing (being thicker than standard ATX PSUs) also helps to dissipate heat
You could probably run these PSUs without a fan if you just give it some airflow, even just a regular household fan would most likely work as long as it is enough to push the stagnant air out since there is so little heat to dissipate. Removing the fan won't work though as the PSU senses the fan and will fault if it does not see it running, very likely for the protection of the airflow for the server.
These variations of the PSU is most likely taken care of by the BIOS on the server but with the adapter these things could be missed if all the variations of PSU are not tested.
In any case, from what I've seen so far, there is one that works with the on-board pot and the other not.
Still, the simple resistor works and there is no need to make any actual modifications to the board or anything and like Sidehack said he is going to address this in the later revisions.
Thanks - I may try that. I just picked up a batch of 16 of these supplies from a local guy today. Just finished going thru them all because there were some different variants in there. I also tested the 6 PSU's I already had just to verify their behavior.
I've got 9 Rev A00 's that all turn on and the fan speed knob works as expected
I've got 3 Rev A08's - that turn on - but the knob won't regulate the fan speed
I've got 2 Rev A00's - that turn on - but the fan speed knob doesn't work (strange)
I've got 3 Rev A02's - that are all completely dead. I think they're really dead because I don't even get a power LED on them when I plug them in.
I've got 3 Rev A03's - that turn on - but the fan speed doesn't work
and I've got 2 Rev A05's that turn on - but the fan speed doesn't work.
I've got more than enough of the Rev A00's to power what I wanted to power at this point. Just thought this information might come in useful.
Seems like the first one of the boards I used - had something happen to it. The fan speed stopped working. I went back and retested it on a supply I had previously gotten the fan speed to work on - and it didn't work any more. Used another board - on the same ( A00) supply - and that worked fine.
Question: is there any limit on how many of these boards can be jumped together to load share? I've got four S1 miners - and planning on adding two more. What I'd like to do is take a block of four of these supplies - and jump them together to supply 3 miners. I think that would keep the load down enough on each individual supply that the fans could be run at the lowest speed with no problems.
Currently I'm running one of the S1 antminers - with two of these Dell supplies - with the fans turned down to the absolute lowest setting. It's all in my basement where the temps don't go about 60-65F - and the two supplies are almost cool to the touch.
I'm going to contact Gekko and order more boards so I can get this going and get rid of the Corsair PSU's I'm currently using.
Oh yeah - and thanks for the tip on the resistor. Good to know in case I have to go that route.