Thanks for sharing your modification. I couldn't tell from the photos. Is the fan installed to push air into the t740 case or to extract air? Also, do you have a photo of the PCIe slot power wiring? Wondering what temp does your NIC run at now? Thanks in advance for any info you can share.
I can get some more photos when I take the Thin Client out again.
The fan blows out. The way these are vented, all air is drawn from the bottom of the case and is blown out the top with the CPU cooling fan. Stock, that's the only fan in the case. I didn't want the 40mm fan to compete with, or crate closed loop air flow between it and the CPU fan. Blowing out, both fans are pulling air in from the bottom. All the air coming in goes directly over the NIC heat sink and SSD drive(s). It's really a brilliant layout. If I could have just sped up the CPU fan this would not have been necessary.
I tapped into the 12v rail at the primary filter cap. The filter cap is easy to get to if you remove the PCIe riser card which easily slides out toolless. Right in front of the PCIe slot on the motherboard (bottom right corner of the motherboard) you'll see a 16v100uf electrolytic surface mount capacitor. Just solder onto its leads and then glue down your wires so you don't accidentally rip them out.
When I ran this mod with the clear acrylic cover with a less powerful fan the NIC temp dropped I think it was 6-8 degrees Celsius. It's difficult to measure temp now because by the time I disassemble the case, the card will have cooled down. With the acrylic lid I had made, I could pop off the cover quickly and use my laser thermometer. That's not an option now. I expect the results of this mod are better than what I was getting before due to more airflow.