Tested Good Power Supply, but Buzzes when connected to Mother board

[Worthlesskiwi]

My Grandma gave me her computer recently because it had stopped working and has asked me to figure out what. When she hit the power button nothing happened. My first thought was to test the power supply. Which i did using a multi-meter, all of the cords produced the appropriate 12, 5, and 3 volts. And while testing the PSU it seemed to work as it should. fans spun and made PSU noises. So i plugged everything back in, and the PSU started buzzing as soon as i plugged in the power cord. The fans wasn't spinning, but it was making a buzzing noise. I hit the power button and the computer did nothing. So why would the PSU work fine while testing it, but buzz when i have it plugged into computer?

 

[samuspunk]

maybe the PSU is old and the capacitors are bad. Due to this, with load, it can´t maintain a stable voltages and doesn´t turn on.

 

[Worthlesskiwi]

maybe the PSU is old and the capacitors are bad. Due to this, with load, it can´t maintain a stable voltages and doesn´t turn on.

What is the possibility of that?

 

[samuspunk]

how old is the PSU?

 

[Worthlesskiwi]

how old is the PSU?

Pretty old....

 

[samuspunk]

So buy a new one, there is nothing much you can do.

 

[Worthlesskiwi]

So buy a new one, there is nothing much you can do.

Lame, but i guess if thats the issue