Hello NeXT Community: So you just bought or received a NeXT Cube. the very first thing you should do is open it up , clean it out and make sure everything is secured.
I've been working on NeXT hardware for 27 years and I had never experienced this before where
the internal drive harness is not secured to the power supply. So it happened back to back and I am so used to the power supply being attached to the harness with 4 magnesium hexhead screws that never gae it second thought until now. The first Cube someone wrote bad power supply but the power supply is fine they did not have the front bezel secure to the faceplate so the power supply was not able to mate with the backplain.
The Cube that just came in had the dimension board in the far right slot , it should go to the left of the power supply and it was reported not to work. The top internal drive harness was not secured to the power supply and it looks like they did this so they would be able to access the scsi2sd card reader by sliding the top half out. So I'm sweating a little bit and zaaaaap I'm electrocuted the cube was not even powered on but I had the power cord plugged in and when the harness moved it made contact with me and I became lit up like a christmas tree for a few seconds . Complete how to disassemble here :
http://www.blackholeinc.com/docs/NeXT%20Service%20Manual%202%20Sections%201%202%203_OCR.pdf please note unplug cube ....
The whole power supply and drive harness slides out easily together what is needed is an easy access mounting bracket design for scsi2sd's perhaps a plastic faceplate bezel the fits into the optical drive. I usually just velcro them internally so you can easily access them. It also was an early model 152 power supply :)