Glad I found this! Came home today and im like you have my Helix turned on a lot of hours as I use it for my soundcard and also sometimes forget to turn it off overnight.
Mine is also and early version bought early in 2016 and is in daily use. Came home today and house was all black, main fuse had been flipped. After a while I go to my PC and turn on the Helix (its connected to a remote outlet so the outlet hadnt been turned on after i flipped the fuse on again) turned it oin and only the small lcds flickered on the unit, smelled a bit burnt electronics in my room. After a while the small lcds displyes the labels, big lcd is black so i fired up HX edit and it finds the helix like usual but small lcds are flickering, starting a backup and halfway through the helix makes a popping sound from the power side and house turns black again. Opened it up and it's the same with mine, diode is burnt etc so im guessing power supply failure, i mean it happens with PC's as well etc. Its now all dead and black so im ordering the PSU you wrote and see if it helps, its 8 years old so warranty is out anyways. To bad tho the price on these things have risen 1/3 since i bought mine haha.