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This is going to start out as just being copied directly over  from my thread on BitBuilt about the project.

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The xbox has some mildly odd power requirements. It uses the same 20 pin Molex MiniFit Jr connector that an ATX PSU output, however the pinout is completely different.
image.png.6d289d30fe3e6334739bcfbb0ffc4cff.png

As it stands, the typical solution is to use a PicoPSU, a small ATX PSU, a modify it to work with the original xbox.  PicoPSUs can be had for around $15, the power supplies for them can be had for around $10.  It's a very inexpensive solution.  Traditionally when this is done, the Power OK and Power On lines are ignored, the PSU is set to always on, and the wires are run all catywumpus to get to where they need to go.  While this solution works, it's definitely a hack, and I believe we can do better.

 

So what are the xbox's actual power requirements?

While I haven't actually cut up a power supply and tried to get the xbox to full load while measuring the current draw, I have a V1.1 PSU here that handily has the power requirements right on the label.

Max Output Power: 96W

DC Output:

+5V -- 13.2A

+3.3V -- 4.8A

+12V --1.2A

+3VSB -- 0.045A

I hope it's safe to assume that further revisions of the xbox had similar or lower power draw.  Regardless, this seems like a good starting point.

 

So, how do I plan to accomplish this?

With 4x LM2678 Regulators from Texas Instruments.

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Why 4 regulators for 3 voltages?

The LM2678 is a 5A regulator. I need 13.2A on the 5V line.  Having looked at the specs for the PicoPSUs that seem to work just fine, they're rated for 8A on the 5V line. This leads me to believe that 10A should suffice, so I'll need two regulators for 5V.

I'll also need a 12V regulator, as I plan to run this off of an easily obtainable laptop power supply rather than needing to source an 8A 12V supply.

I will also be designing a smaller footprint alternative that runs off of 12v for when space is of the highest concern.  I'll likely also break down the xbox's power requirements even further at some point to see if I can't design a PSU that allows for aggressive trimming, but that's much further down the road.
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I've designed the first iteration of the 24v board, it's 60*32mm. Now that it's done, I don't like it for a variety of reasons. I'm going to try again, putting the low profile components on the backside of the board and the tall components on the topside of it. Maybe I'll be able to squish it down a bit more in the process.
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image.png.50f0cee6f3783ae35991538d20b3667f.png

There, that's a little better.
27.5*49.25 mm
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Oh, hey, I worked on this a bit.
I ditched the 12v regulator and changed it to 12v in. I also had to source different inductors, which are sadly larger, so the whole board got a couple of mm wider in the process.
image.png.c5b2784d85afbc13adba612a483e6a98.png

26.5mm*57.2mm

I think I'm gonna actually order this one, and see if it works.

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I've since looked at the most recent revision and noticed a couple of flaws in it. I've repaired those flaws, and I'm gonna sleep on it again, look at it with fresh eyes tomorrow, and probably order it.

Edited by ttsgeb
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Interesting project, I'm using a pico psu (160XT) with atx to xbox adapter and due to the low amperage on the 5v line the xbox struggles to initially boot as there are a lot of capacitors that need charging. I resolved this slightly by removing 3 of the start up capacitors on a v1.0 xbox and while it works I'd prefer a much more professional and reliable solution 

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6 hours ago, ShinGoutetsu said:

Interesting project, I'm using a pico psu (160XT) with atx to xbox adapter and due to the low amperage on the 5v line the xbox struggles to initially boot as there are a lot of capacitors that need charging. I resolved this slightly by removing 3 of the start up capacitors on a v1.0 xbox and while it works I'd prefer a much more professional and reliable solution 

2 options

Use a bigger Pico (300watt) PSU or use a version 1.6 Xbox fitted with a 2.5 inch HDD using the 160XT

 

Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

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Unfortunately size wise the higher wattage pico psu's are too big for my xbox mini so I'm currently limited to the 160XT. I am using a 2.5" hdd already, as I said it works it's just not as perfect as I would like. The board I am using has 128mb ram so I'd rather use that than a v1.6 board

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Well, you said "Professional" and while that certainly doesn't describe me, it made me reconsider the hack that probably wouldn't work that I was going to try to get this working, so I went back to the drawing board and started over.  Instead of trying to put two switching regulators in parallel for the 5v line, I'm going the proper route and designing it with a controller and mosfets per the suggestion of TI's WEBENCH Power Designer application.  I'm still going to have to do some tweaking to make their suggested circuit into something I can reasonably hope to assemble, however.  As an added benefit, my new 5v circuit will definitely support the power requirements of the xbox, and won't be prone to the same issues that the 160xt apparently has.

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I've gotten the new schematic thrown together, next up is assigning footprints to everything and laying out the board.
I'm definitely considering a PCB assembly service for this one, that's something like 35 components, most of them 0603, and I really don't want to have to put it together.

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That reminds me of the version 1.6 PSU.

You really should assemble the 1st/prototype yourself that way if there is a problem you can sort it out.

 

Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

 

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The difference between this and the 1.6 PSU is that this is, so far, smaller than a thumb drive.
I've gotten the 5v circuit laid out now.
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11mm*40mm
The 3v3 and 12v circuits are going on the backside, the power jack on the left and the outputs on the right.  Should come out to something like 12*60mm, or 1/2"*2 1/4".

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I was going to update the post, but apparently we're only allowed to edit for a few minutes.
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I've gotten the whole circuit laid out now. We're once again at the "Sleep on it" stage where I take a nap and then decide how I feel before ordering anything.
20.5mm*56.5mm, or slightly smaller than the fan cutout in the motherboard.

Edited by ttsgeb
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Well, I just ordered everything I need for the first build. $76. I really hope this works.

Future boards will be under $30/each if this design works out, but that's with me assembling them, so there's quite a bit of time involved there.

If it works, I plan to open source it so that anyone that's feeling daring enough can make their own. I'll probably also offer a few for sale, but they won't be cheap. I'm expecting to charge around $100, but ultimately it depends on what I can get them made for.

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Sounds good and I am sure that they will sell.  

 

Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

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Boards came in today
IMG_20200605_080552.jpg?width=974&height=1298
IMG_20200605_095201.jpg?width=974&height=1298
Assembled and tested, the 3v3 line works as expected, but the 5v line doesn't work at all. I'm assuming it's due to a poorly aligned chip that I didn't notice until after I plugged it in. I re-aligned the chip and the problem got worse. I'm pretty sure that chip is fried.
I also ran into a problem with the power jack, apparently either I read the datasheet wrong, or the datasheet was wrong.  Either way, I had to solder a pigtail jack on to get power to the board.

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4 hours ago, ttsgeb said:

Boards came in today
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Assembled and tested, the 3v3 line works as expected, but the 5v line doesn't work at all. I'm assuming it's due to a poorly aligned chip that I didn't notice until after I plugged it in. I re-aligned the chip and the problem got worse. I'm pretty sure that chip is fried.
I also ran into a problem with the power jack, apparently either I read the datasheet wrong, or the datasheet was wrong.  Either way, I had to solder a pigtail jack on to get power to the board.

That sucks. Hopefully it is just a fried chip, and not a board issue. But I guess that's part of the whole process of designing a board like that.

When all is said and done, what will you call the first released board revision?

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Idk. Bob has a nice ring to it.

I'll be ordering a replacement chip and a components kit to build a second one tonight. Hopefully this time next week, I'll have a working board.

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1 hour ago, ttsgeb said:

Idk. Bob has a nice ring to it.

I'll be ordering a replacement chip and a components kit to build a second one tonight. Hopefully this time next week, I'll have a working board.

I like that idea. First revision "Rev Bob". Definitely something that would be memorable.

I look forward to the update for the next attempt.

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On 6/5/2020 at 7:58 PM, ttsgeb said:

I'll be ordering a replacement chip and a components kit to build a second one tonight. Hopefully this time next week, I'll have a working board.

Any luck with the new parts?

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No luck with the new part, I'm going to try just building the 5v circuit on the second board and see how that turns out, but I'm not holding my breath.  I just wish I could track down what I've done wrong.

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What is the 5 volt doing ?

 

Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

 

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Have you tried powering it up with a load on the 5 volt?

 

Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

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The datasheet said nothing about no-load shutoff, and I didn't build that into the circuit, but I gave it a try anyway.
No change. I'm still seeing nothing from the 5v and perfect behavior from 3v3. I'll make sure to have a load connected on my second build before powering it up, though.

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7 minutes ago, ttsgeb said:

The datasheet said nothing about no-load shutoff, and I didn't build that into the circuit, but I gave it a try anyway.
No change. I'm still seeing nothing from the 5v and perfect behavior from 3v3. I'll make sure to have a load connected on my second build before powering it up, though.

What part did you use for the 5v circuit?

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31 minutes ago, ttsgeb said:

The datasheet said nothing about no-load shutoff, and I didn't build that into the circuit, but I gave it a try anyway.
No change. I'm still seeing nothing from the 5v and perfect behavior from 3v3. I'll make sure to have a load connected on my second build before powering it up, though.

Do you have an oscilloscope available to you so that you can see what the 5v line looks like?

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I have one of these kicking about somewhere that I can track down tonight and try to get a scan of what's going on, but I suspect it'll be more of nothing.
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