Sorry for not responding sooner about PSU of TNN-500AF.
The PSU of my TNN-500AF recently failed as well so I totally gutted it and I decided on an external PSU solution. It literally made a popping sound when I tried to turn it on one day, so I decided it was time for a new build. That really was my greatest fear with this case as I knew this PSU's lifespan was beyond its intended lifespan. I even tried to source a matching replacement Zalman PSU for this case to no avail, well before it failed on me! My new build is currently work in progress and I will be sharing the finished results publicly soon. I decide to gut/remove the fried PSU of the case for a cleaner look because the cables of the PSU were not modular.
There are benefits of having an external PSU. For one, you can get a far better (more efficient, more powerful, & modular) PSU since what was packaged with the TNN500 is now 9 year old tech! Also, you are removing a chunk of heat from the case and allowing for lower temps of your other components. It’s not like we use our 90 pound TNN500 for portable computing so I don't mind the extra step of disconnecting the modular cables of the external PSU to work inside the case if the need ever occurred.
As you can see, squeezing a standard sized PSU inside the TNN-500AF would be impossible in my situation since I’m using a 2 slot video card, a raid controller card, and a PCI-E SSD. All PCI slots would need to be empty in order mount a PSU on the side door if utilizing the lower section. Top section of case door is now occupied by 4 SSDs & DVD burner. I actually had to downgrade to low profile RAM/memory because I couldn’t close the case door since the case plates that the SSDs are mounted to were impacting the heat sink fins of the memory. Short of powerful swing(s) from a sledge hammer, there’s simply no physical way to squeeze the case door shut regardless of where you try and place a standard sized PSU within my TNN500 rebuild.
Besides, when optimizing for heat dissipation, the PSU is best placed outside the case. I took this a step further by opting against integrating the GTX 650 with heat pipe integration and settled with a prebuilt passively cooled solution instead, this time going with ATI. The video card would be the largest source of heat residing within the case since it draws the greatest amount of power at full load, yet without heatpipe integration, this will allow for lower temps for case and in return, lower temps for PCB & CPU. Sure, this translates to a hotter GPU, but I’d rather swap out a fried/failed video card than rebuild the entire system because of a fried capacitor on the motherboard. I also like to upgrade video cards regularly. Heck, I’m already on my 4th video card upgrade over the course of this TNN500 rebuild, so I wouldn’t want to mess with swapping heat pipes each time anyways.
My latest build utilizing TNN500 should be completed before xmas and I’ll post a new thread to share. Then you can decide if an external PSU solution is elegant or unacceptable in your opinion.