@grendel Sure you're certain you need a new cable harness?
A few years ago, I replaced the HDD power switches myself, they’re just small smd transistors.
1 and 2 (Channel A) power on simultaneously, followed by 3, 4, and 5 (Channel B).
There’s a built-in delay between the two channels to help manage voltage spikes that occur during HDD initialization — Channel A starts first, then Channel B.