dead powersupply or motherboard?

[shayan44]

my computer was working fine no problem shut it down turned it back on after 30mins nothing.no display or light.
green light on motherboard tho tried jump starting nothing and green light on motherboard gone too
tried new powercable everything working fine on only first boot shut it down tried to start again again...nothing tried jump
starting too sometimes no reaction but usually when i hold on power light and power from cpu fan starts and when i let go it stops but no display but if i keep holding power it shuts down automatically after few seconds.
i also tried disconnecting everything and booting it out of case
my doubt is on powersupply cause sudden poweroutages in my city and slight voltage fluctuation(but i use stabilizer for tha)t but i have close to none experience with desktop computers

my specs are
intel i5 3330s(stock)
asus h61m-e
coolermaster gx450
ddr3 ram 4gb 1333mz
ddr3 4gb 1600mz

EDIT:after plugin in back i gave it another chance..it booted after a sometimes just casual chrome browsing it cut off power

 

[CountMike]

It's easiest to start with PSU, some known good and of appropriate wattage. Do you have a dedicated GPU too ?

 

[shayan44]

It's easiest to start with PSU, some known good and of appropriate wattage. Do you have a dedicated GPU too ?

i will go to a computer store with my mobo and check whats the issue i bet its psu tho.
i think my wattage requirement is 400-450 i dont have a gpu yet but iam gonna get 1050ti in future
recommend me good psu around 50-60 usd and no seasonic cause i never seen them in my country