PSone power supply to switch issue

Hi everyone, and thanks for reading my post.

I recently bought a very cheap for spares/repair PSone on ebay with the description 'completely dead'. Being the nerd I am I thought 'I'll have a go at fixing that'. We've all been there haven't we....

Once in my grubby mitts I quickly discovered that all the usual culprits were not the cause. Power supply good. Yellow DC adapter on motherboard cleaned up and working fine. All solder joints good, Power on/off switch tested in isolation and found to be working. So the fault lies in between the power adapter and the switch somewhere....

I've tested all the fuses that I believe are involved between the power supply and the switch and they are all good. I'm clearly missing something here as there is no power to the 'supply' side of the switch when plugged in.

I desperately need a wiring diagram showing how the power gets to the on/off switch but can't find one anywhere. Can anyone help me please? Do you have a wiring diagram? Have you had the same problem??

Hopefully there is someone out there who knows where I'm going wrong and give me the answer I need. I'm convinced it's simple, but don't know where to look.

Hoping to get some good advice!

Regards

GrahamT