Hi Alexander,
Mine situation got worse over time. SATA1 doesn’t spin up, or if it adds with the SATA2 and emits ‘beep’ style sound generated by heads. They are both powered by the ‘b’ rail.
I used ATX 12v DC instead of the provided power supply, same results. The only way to operate requires an ATX SATA connector. My setup is 5*3″ 5, I am not sure I would be a good idea to merge them on the ‘a’ rail.
I enjoy this kind of DIY NAS and I ordered on ASRock JTX board. I might come back later to try what wrong but I am afraid some SMD on the board is involved. Today, buying a new case, add an ATX power supply is the only option.
Oli