Question Computer repair gone wrong running out of ideas

[Tfish298]

I recently started a small business in computer and electronic repair, but the computer I’m working on currently has stumped me, it was running perfectly fine until someone swapped the power supply in it, and then it suddenly started constantly boot looping, I replaced the power supply, motherboard, ram, cpu, and even tested different ram sticks, and gpu’s I had lying around, at this point the only thing I haven’t tried is taking the parts and putting them in a different case, the pc no longer boot loops but will now restart three times, turn on a fourth time, but that’s it, no display, no beeping, nothing. I am at a loss on this one and have already had my client waiting for so long and the parts keep racking up the bill, does anyone have any suggestions or should I just call this one a loss and buy a new rig save for the pieces I already have.?

The pc specs are
I5 6500 cpu, gtx 1650, thermaltake 500wpsu, 16gb of ram

 

[boju]

What motherboard is it, does it have video ports? Try no graphics card and disconnect any and all storage drives.