It’s been a long time since I’ve posted any updates here and now it’s time to fix it.

First, the project is not dead! I had to take a break from it to work on several other things in the meantime, and since there are still issues which I don’t know how to fix yet, it sometimes feels just a little bit discouraging to go back to it.

There are two main issues with the prototype at the moment:

  1. Stability issues. This could be just the console I’m testing on but sometimes it works for hours and sometimes it shuts off after a few seconds. A single prototype that I sent for test to another person works great and there were no issues reported, so I’m a little lost here. Probably need to buy one more Xbox for tests.
  2. Despite it working relatively well with PicoPSU, I wasn’t able to make it work with a regular PC PSU, it simply doesn’t start. I see a fan in the PSU spinning for a moment and that’s it. No other signs of life. One reason could be that it’s probably drawing too much current from 5V standby line but it needs more testing.

I’ve got a clamp ammeter to easily monitor the current draw and from what I saw my Xbox is drawing between 5 and 7.5 Amps during the power on cycle on the 5V standby line when using the prototype adapter with PicoPSU. I don’t know if it’s working differently and somehow is able to tolerate high load on this line or if I’m simply doing something wrong here.

The draw should definitely be on the non-standby 5V line and I guess this is where the main difference between ATX PSU and Xbox PSU lies. I need to find a way to feed the 5V standby line of Xbox motherboard from a corresponding line of the PSU and then, when the console is being switched on, to switch the lines and start powering both 5V and 5V standby lines from a 5V line of the PSU. I currently have no idea how to do that. Should I use a relay or some form of a transistor? Or, since if it’s so against the way ATX power supplies work, wouldn’t it be more logical to design not an adaptor but a completely new replacement PSU which could be powered from an external power source, just like replacement PSUs for SEGA Saturn or Dreamcast? The problem is I don’t have any experience building such things and when it comes to power supplies I prefer to rely on other people’s products which were properly tested and certified.

I’m starting from the beginning now, this time using the PC power supply which should provide better compatibility in the future. And before ordering the next prototype PCB I’ll make sure that my method is working reliably. I went through 12 revisions of the current board, spent a lot of time and money, and still wasn’t able to make it work the way it should, I don’t want that to happen again.

I’ll go back to the ATX prototyping board, wire it to Xbox motherboard and keep trying. Hopefully there will be some new developments.

Until then, wish me luck and see you in the next project update!