It is never recommended to open a PSU.
If the PSU does not power on it needs to be replaced.
If you describe your problem and include your specs, as listed below, we can probably assist you.
Pre- Built Brand & Model Number
Custom Built- Brand & Model of Mobo-CPU-RAM-Graphics-PSU.
Short answer: The power supply is garbage, and it is probably dead. you should never try to fix a power supply.
Long answer: Low quality, no-name brands are always bad quality. Chances are if you tried to pull 350 watts from it, it would explode and/or catch fire.
Servicing a PSU is very dangerous. For you. They can store a near lethal electrical charge even hours after being powered off.
Spend $80-100 on a NEW seasonic - XFX - corsair (no gx or bx)* power supply, and have it last for years, rather then spending only $20 on a no-name one, every six months, and the an additional $800 on a new computer
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