Monitor keeps going black after ...

[Suspekt]

Hello,once again I am asking your help because some strange bs thing happened that makes me go bananas and to be honest I've never seen stuff like this at no one. So the problems is the following:

I bought a new headphone yesterday ( my older one died ) I tested it at the store at the clerks PC to see if it sounds how I want it and it is balanced for what I need it for ( I'm a music producer ) it was all good and obviously I bought the headphones.My problem started after I got home and plugged my headphones in to my MAIN sound board ( the onboard card is disabled from bios ) and my monitor ( a Horizon ) just went blank.I plugged a bunch of headphones while the pc was on,the same thing did the clerk at the shop so I can test it out and nothing like this happened but now for some unknown reason my screen started flickering,going blank from 30 to 30 seconds and only after I powered off and on the monitor it started " working " for a few seconds and then again going off until I switched it on and off. Now here is another info, my monitor has build in speakers BUT the cable from it was plugged in the onboard sound card which was DISABLED and so were the speakers from the monitor ( I plugged it in so it won't hang loose a few years ago )
What could be the problem? What connection could there be between me plugging in the headphones and my LCD going nuts even though the other soundcard is on disable. My first answer was some kind of " shortage " but it doesn't really makes sense since my onboard card is disabled and my main sound card has no connection with the monitor itself ( except that they share the same motherboard ) but stuff like this still shouldn't have happened and it never did until now.

Thanks

 

[rvcjew]

Disabled or not metal touching metal is contacting each other. Maybe when you plugged it in it spiked through the back panel of the system (I/O shield) sounds crazy but could theoretically happen. What headphones, maybe they tried to pull to much power (High impedance?) causing the issue. Try re-plugging in the monitor cable and unplug the speakers from the disabled port.

 

[Suspekt]

Apparently somehow it blow out my psu from the LCD that was feeding the CCFL lamp/invertor ( I have no idea how could've this happened from some headphones, never heard of stuff like this ) The headphones are from Pioneer but i don't think it was " draining " too much power (my PSU from the PC is pretty good with all kind of fail safes)... Eventually I ended up taking it to a service and they be willing to change that part for 40$ smh ...

 

[rvcjew]

At least the repair does not sounds super expensive. But yeah situation seems odd to say the least.