A500+ doesn't start with A590

[IlyaZ]

The A500+ starts independently, but when I connect the A590 HDD the A500+ green light doesn't turn on. The HD spins up and gets power. Switch is on 1 which is autoboot. I should add that the original A590 PSU did not provide power, so I went ahead with what I suspect is a vintage internal PSU I found lying around that had the same connector modded onto it, which at least gave power to the unit.

[IlyaZ]

It says Hard Drive Plus A590. "Switch" on the back 1 through 4. 1 is in the up position.

[IlyaZ]

Yes, power light doesn't turn on. PSU 5V output at fault? I'll check with a multimeter. If not, could a short occur on the A590-side? Capacitor that turns short instead of open?

[IlyaZ]

Edge connectors seem clean, also cross tested with another A500+ with the same result.

Why do bad chips turn hot, just end up getting higher resistance?