Not sure what happened to the upper front fan but it does not work anymore. Testing the fan shows it has completely failed. Retesting the extension cables show them to be fine.
The OEM fan is marked as A1425L 12S-2 with power draw of 300mA. The cable is a 3-pin so it used DC power management. 4-pin fans can use PWM power management but that is rare with case fans.
A replacement 140mm fan is available in the studio so replacing it took little time. At least now all of the fans are now working properly which is affording the machine better temperatures. Its prudent given that fans do fail to have a spare or two on hand.
After replacing the fan, the disk cage (CC-89300320) was delivered so it has been installed. It is secured with standard 6-32 screws to cage below but there is no apparent attachment for the top of the assembly. The upper 5¼” cage has a lip that keeps the upper cage in place securely but no screw holes were obvious. The capacity for 9 discs is more than many NAS users which makes the 750D worth its cost. The 8-port SATA card easily supplements the motherboard ports.
Given that the machine has while LED power and disk activity lights, to be consistent white LED fans would make for a comparatively brightly light machine. Corsair photos show the 750D with blue LED fans but the new white LED fans are widely available.
A quad port 9-pin USB hub was installed to replace the lost ports from the defective Commander Pro. The hub makes it convenient for the range of USB devices seen on machines. The AX200 card needs USB for the bluetooth to work while the 750D chassis has two USB 2.0 ports. The HX1000i and the H115i also need USB for monitoring. The only real power draw potentially is the front panel but USB flash sticks use negligible power themselves. Few use USB 2.0 ports for charging devices anymore.
The remaining 2-port USB hubs are not needed at the moment as the single 4-port unit covers all of the requirements. Having available internal USB 2.0 hubs has become a standard item to have handy when installing hardware in a build.
No PCIe cards have been seen with multiple internal USB ports similar to USB 3.0 cards. Years ago PCI USB 2.0 cards were common to expand on the limited number of ports on machines in the latter 1990s. USB 3.0 gained grown slowly. Older chassis like the HAF 932 only have four USB 2.0 ports while the 750D has two USB 2.0 and two USB 3.0 ports.
USB sticks are still widely used. For example its advisable to have one in case Windows becomes unbootable. Similarly a USB stick for Linux is needed to recover an unbootable machine. Smaller capacity 16GB or 32GB hardware is quite adequate at present.
Tape is holding the front grill in place which seems to be the best solution as the vibration is fairly high.
Besides the dead Commander Pro is now the dead chassis fan. It seems that quality assurance is going downhill. Then there is that keyboard from Razer that malfunctioned and useless, no warranty there either so a reminder that claims that are not honored can attract legal complaints.