Log The Miniproject (custom mini-STX)

Engineerer

Cable Smoosher
Original poster
Oct 29, 2020
10
9
Hello all! I though you guys might appreciate my recent mini build. The project was originally posted in a non-english forum and this will be pretty much translation of the original.

I wanted to build a gaming capable HTPC for living room and I wanted to build to be as small as possible. Mini-ITX would have been too mainstream and simple, so I chose Mini-STX form factor. As there really isn't Mini-STX motherboards available separately, I chose Deskmini A300 as a organ donor. Case for the build was going to be old Nexus RX-8500 PSU case with 86x150x164,6 mm dimensions. This provides just enough added room to include dedicated GPU in the build.



A300M-STX motherboard doesn't actually have interface for the dedicated GPU, but this interface will be provided by a m.2 -> PCI-E adapter. The adapter provides PCI-E 3.0 X4 for the GPU. Usually motherboards have X16 interface, but this shouldn't be too much of a bottleneck as GTX 1080 level GPU will only loose few percent when used in a X4 link.

Deskmini's power adapter can only supply 19 V 120 W for the whole system and its missing 12V rail, so it won't be suitable for a system with dedicated GPU. Easiest way to power the system will be one powerful 12 V as A300M-STX is able to run from 12V.

Based on size, performance and efficiency I chose Palit GeForce GTX 1660 Super StormX as the GPU for the system. The graphics card is barely longer than the PCI-E X16 connector and it's mostly longer because of the cooler's lengt not actual PCB of the card.




I chose Ryzen 5 3400G as the build's CPU as it is the fastest available. Based on reviews Deskmini consumes around 100 W with this CPU and GTX 1660 Super will add another 130 W to it, so overall power consumption will be around 230 W. Egpu build often use Dell's old DA-2 power adaptors, but these are only 220 W, so it won't be enough for this. Another option I found was to use Mean Well's 252 W GST280A12, but also this might not be sufficient for the build. Finally I ended up with Phihong's 288 W power adaptor PPL300U-120 I found from Digi-Key. This power adaptor costed around 120 € with added customs duty.

I started off the build by doing STX form factor attachments for the mainboard and cutted rear of the PSU case open for io connector.
 
  • Like
Reactions: aromachi

Engineerer

Cable Smoosher
Original poster
Oct 29, 2020
10
9
As the height of the case will be limited I cut the motherboard risers as short as possible while bottom side components still had small gap under them. I removed old PCI-E power socket from the old PSU as this will be used to power the complete system. Also the 8-pin power connector for the graphics card is salvaged from the old PSU.

Parts on the floor, wires connected and smokes out. Luckily there weren't really any smoke and the system booted immediately after power button was pressed. Video output was working automatically from the dedicated card.
 
  • Like
Reactions: thewizzard1

aromachi

Cable-Tie Ninja
Dec 18, 2019
150
137
Mini-ITX would have been too mainstream and simple

I feel the same way about all the mini-itx cases available on the market. Its just.. boring. Case arrives all shiny and new. You got your build order spelled out for you. Minimal brain power required. Ugh..boring. Glad you found a project that appealed to you. Ever since the a300 Ive seen a lot of these PSU builds, but you never ever see them done the same way twice. Good luck! Watching!
 

Engineerer

Cable Smoosher
Original poster
Oct 29, 2020
10
9
I feel the same way about all the mini-itx cases available on the market. Its just.. boring. Case arrives all shiny and new. You got your build order spelled out for you. Minimal brain power required. Ugh..boring. Glad you found a project that appealed to you. Ever since the a300 Ive seen a lot of these PSU builds, but you never ever see them done the same way twice. Good luck! Watching!
I was hoping that my PSU case idea would have been original when I started. It was kind of disappointing when I found that similar builds were already done :D Well as you said every PSU case is still done differently.
 

Engineerer

Cable Smoosher
Original poster
Oct 29, 2020
10
9
To minimize the height I placed cooling fans between two heatsinks. The bottom heatsink is for the CPU (Noctua L9a) and on the top will be graphics card's heatsink. I replaced the connector from the 92mm Noctua fan so it could be controlled by graphics card. The smaller 70mm fan will be controlled by CPU.



All I/O connectors will be on the back side of the case. I will be using opal white acrylic sheet as a back wall of the case. Required openings will be milled to the acrylic sheet.



Here we have milled openings for the I/O plate and additional USB ports.



When I salvaged the PCI-E power socket from the old PSU I cut it off with a small PCB piece still attached to it. This old PCB piece will be used for power distribution and it also provides some mechanical support for the connector. The PCB is attached to the acrylic with a M3 screw.



And here we have a trial assembly. M.2 -> PCI-E adapter is wrong handed as the ribbon cable raises upwards and won't fit. Also the back wall is leaning backwards as some milling has not yet been done to the acrylic sheet. It's a tight fit, but it will fit.

 
  • Like
Reactions: aromachi

Engineerer

Cable Smoosher
Original poster
Oct 29, 2020
10
9
Fit testing for a custom power button. The button was just around 4 € from China. Not very nicely finished, but good enough. Lightning bolt seemed to fit the PSU theme.



 

Engineerer

Cable Smoosher
Original poster
Oct 29, 2020
10
9
And here is the front plate for the power button and WLAN/BT antennas. Same acrylic sheet used here as in the rear of the case. Two TE 2344657-6 antennas can be seen behind the plate. These were easy to attach with their own adhesive.

 

Engineerer

Cable Smoosher
Original poster
Oct 29, 2020
10
9
Build is starting to be pretty much complete. I added Corsair's 135 mm fan NR135P on the top of the case to get temperatures in check.

At first I had some issues with the fan as it was always going full speed regardless of the PWM control from the motherboard. I disassembled the fan and found out that the PWM trace is not connected on the PCB. On the PCB There was a IC with 90287 marking on the top indicating that it was a PWM capable fan controller MLX90287. Examining the datasheet of the IC and the PCB I came in to conclusion that the PCB was missing only one 0Ω resistor for PWM control. I shorted the resistor placeholder with solder and PWM control started to work normally after reassembling the fan.

I don't quite get it why there wasn't this 0Ω resistor already as PWM fans are always at full speed when the PWM signal is missing. Therefore also DC voltage control should work just fine even when the resistor is placed.







 

msystems

King of Cable Management
Apr 28, 2017
781
1,366
Just found this while looking up that power brick on google. Surprised nobody responded as this is very compact build and interesting concept of sandwiching the fan between two heatsinks. We see that on CPU heatsinks a lot now. I wonder how a push-pull configuration on the sides would turn out, instead of the fan sandwich (perhaps if the case could be made custom).