Really, maybe mine was a defective fan Because I changed the fan right from the beginning when i set it up for the first time. It ran fine with the clock at 500. It was when I started testing the overclock that's when the trouble was seen in temperature and i changed the fan with a 5400rpm I had already. I'll check the new one when i get it. I only bought 1 so I was working from no reference. I wonder if more were using a 3000rpm fans. Anyone?

My Batch 1 mini came with a 3000rpm fan. I replaced it with a 5400rpm fan. set it to 100% and the clock at 750. In this config I have 1 board reaching 70deg C and the other 2 are below that. The boards are in the 55deg C range. I have a second batch 1 mini coming in a few days and I have a 6000rpm fan i will use with that one. The seller states it runs at 16kh/s as is but I feel better with the high speed fans.

Here is more data
When I am hashing at 16.9 kh/s the share rate on ZEN, @ suprnova, my share rate for the 16.9 kh/s, with 1 controler (original) configuration, is 913. In the 2 controller configuration it's 1010.
My Efficiency dropped from 99.9 to 98.8 respectively.
Round earnings went from .0367 to .0404 respectively.

I purchased a 2nd controller board off of ebay. I have the fastest hashing board in slot one and then hashing board 2. Slot 3 is connected to the second controller i got off of ebay. Mine is a batch 1 unit. so i have 2 controller boards connected to the same pool, so the hash rate is totaled at 16kh/s combined but I have 2 workers in the pool. I get about a 10-15% increase in the number of shares processed. I had to connect a fan for the external controller to work. But like i said earlier that luck drops in this config.

I have One Controller flashed with the 750 firmware. I did this to up the share rate by using 1 card from my version 1 Z9 mini. It did up my share rate as it seams, one hash board is enough to do the work and my coin rate went up using 1 Z9 as 2 Z9s. Both overclocked at 750 with a 5500rpm fan the highest temp is 70C. But, as I learned more about using the miner in this way it ups the share rate with a combined hash rate of 16.5 KH/s. But your chance or luck to find a new block goes down. I just purchased a second version 1 Mini and I will be able to make 3 miners running 12 kh/s for a total hash rate of 36K on the pool and an even higher share rate; but again Luck goes down in this config in finding blocks. I will try it to see how it works and I will report back.