Blue light then powers off

Hello,

I’m working on a PS4 that’s suffering from a problem I’ve seen mentioned several times on here, and none of the ‘easy’ solutions have worked.

Attempting to power on, the blue light blinks for 7-8 seconds then the console powers off. Well, it seems to, but several power rails are still present and pressing the power button again in this state causes it to turn properly off. This is different to the common “blue light of death” fault where the light supposedly continues flashing until you power the console off so I’m reluctant to try things like putting extra pressure around the APU just yet.

I noticed also that the USB ports have no power present during the power-on attempt, I don’t know if this is normal, but the ports have clearly been replaced before so I’ll assume there is some fault with the USB hub controller chip or power circuitry.

Given these symptoms, is this likely to be a USB fault? Or should I try other fixes first?

Thanks.

UPDATE: The TEST signal on the USB hub controller chip is reading 3.2V which means test mode enabled. Is this ever meant to be the case? I don’t see any traces going anywhere visibly besides a probe/test point, but I realise that the signal may be going elsewhere on internal layers. I will replace the chip just in case this is not meant to happen and is the cause of a failed POST.