Power/display issue with PC

[Banzai_Joe]

Hi all,
so built a rig for a friend:
i5-9600k on a Asrock m-itx a/c
16gb ram
GTX1070
500gb m.2
1tb 850 pro ssd
600w leadtek fully modular
Case (now here's the thing...)

So, computer works fine (ish). But if turned off and back on display never works. There is no POST speaker to give any clues.
I have to power down remove plug, reinsert, turn back on.
This happened to me prior to handing it over, i swapped the ram out, but it made no difference.
Then i noticed that the 4-pin power molex (part of the main 20-pin connector) wasn't in correctly. So, after sorting that it seemed to work fine. Then after a day or so my friend reported the issue.
Now, this case, it has a gazillion rgb fans that are all connected to a little box controller and the case reset switch cable, instead of going to the front panel on the mobo, it connects into this controller. So each press of the reset button on top of the case simply cycles through the lighting scheme on the fans.
I've never built a case with a controller like this before so wondering if that might be the cause (guess i can find out by unplugging it). My case is similar but they all connect to the mobo or a power molex, yet still work in the same way wit the reset switch.
But the fact that unplugging, basically dissipating the power to get it to work kind of points towards the psu or possibly the mobo (not retaining capacitance or whatever?)
I dont really have any spare parts to test with, but what would be your checklist order please guys?

Thanks

 

[adrichardson81]

I would definitely try it without the box controller.

In fact you might find it easiest to assemble it outside the case (not on carpet), and see what happens. If you consistently don't get a repeat, then you can start looking at the case.

 

[Banzai_Joe]

Thanks. Yeah was my first thought.
It’s an aero cool case, so not uber cheap nasty rubbish.
So doing a restart seems fine. But a full shutdown then boot up just doesn’t produce anything on screen. Weirdly sometimes just pressing the power button once will shut it down which to me implies that it’s not even booting into windows.
That said, other times I have to press the shutdown button for the usual 4 secs to force it down.
Only way to get the screen back is to unplug, power cycle, even though nothing happens, not even a sniff of fan spin or led light. Plug back in and it works again.
I’ll take the controller off and see what happens.

 

[Banzai_Joe]

Ok, so it’s not the fans/controller in the case as I just completely unplugged them and had the same issue.

 

[ASMB]

Does the CPU fan spin up ok on start up. I had a case which would easily cause a short circuit. The CPU, GPU, etc fan would spin briefly and then stop. I wonder if there is a short circuit in the case somewhere

 

[Banzai_Joe]

Heh, ya know what it was?
The system didn’t like the mild overclock I put on it. Set default settings in UEFI and all is good again after multiple tests.

thanks for the input folks. Case closed.