BMAX B5A Pro fast fan spin + power led but not starting

[dbuergi]

Hi all,

since i can exclude a bios fault i'm looking for a hardware problem on this one. I got this mini pc with no power and a blown up mosfet with damaged ground bad. I cleaned everything and drilled the area until the short was gone and i was able to rebuild everything.
When i plug in the power supply the power led turns directly on and i get the fan on full speed but nothing else. I can power the board off with the button.
The coils don't show any voltages and other measurements are marked on the picture.
There are no hotspot on the board and with voltage injection of 1v and 1a on the big coils i get 1v and 0,6a output and the CPU is getting warm.
On the EN pin of the RT3663BM PWM chip i only get 0,3v so maybe there is something wrong with the enable signal? Shouldn't it be 3,3v? So maybe anything i can try or should i replace the RT3663?

[devicefixer]

Hi all,

since i can exclude a bios fault i'm looking for a hardware problem on this one. I got this mini pc with no power and a blown up mosfet with damaged ground bad. I cleaned everything and drilled the area until the short was gone and i was able to rebuild everything.
When i plug in the power supply the power led turns directly on and i get the fan on full speed but nothing else. I can power the board off with the button.
The coils don't show any voltages and other measurements are marked on the picture.
There are no hotspot on the board and with voltage injection of 1v and 1a on the big coils i get 1v and 0,6a output and the CPU is getting warm.
On the EN pin of the RT3663BM PWM chip i only get 0,3v so maybe there is something wrong with the enable signal? Shouldn't it be 3,3v? So maybe anything i can try or should i replace the RT3663?

I feel like you really need to try and track down a schematic or boardview for this exact motherboard. You drilled into the board, so we have to determine if there were any internal traces running through the layers of that burned area.

If there were internal traces, how many? If it only involved a few traces and they don't route directly into the inner layers of the main chip (CPU/PCH), this board is still salvageable, but it will definitely require running jumper wires.

My advice is to stop guessing. Sticking to a standard, logical troubleshooting sequence will actually be much faster. Check the schematic to see exactly which traces passed through that drilled zone and what components they connected to. Run jumper wires to reconstruct those lines first to completely rule out any broken trace issues .

Once you've ruled out broken traces, look at the schematic to see what that blown MOSFET was actually responsible for. Is it critical? If it's for a minor, non-essential circuit, you might be able to ignore it. But if it's an important rail, you need to mount a replacement MOSFET—either in the original spot or secured somewhere empty on the board—and run jumper wires from its pins to the corresponding components.

After doing that, the physical reconstruction is basically done. If it still doesn't POST or give a display after these repairs, then you move on to checking your power sequence to see if all the rails are coming up. Just take it step by step.