# Problem of having both short circuit and voltages in output of power supply

#### Saeedk9574

Joined Jan 1, 2024
19
Hello everyone,
My computer power supply is short circuit in the output when I test it by multimeter, although it has all the voltages including 12, 5 and 3.3. So what is the reason of that while it provides these voltages and works without problem, but it is short circuit. Is it dangerous to use it in this way?

#### seanstevens

Joined Sep 22, 2009
258
HI Saeed, what makes you think your PC power supply is shorted? How are you testing it? Does the PC turn on as normal?
More details more details...

#### Saeedk9574

Joined Jan 1, 2024
19
HI Saeed, what makes you think your PC power supply is shorted? How are you testing it? Does the PC turn on as normal?
More details more details...
Actually, I do not use it for pc. I use it as a power supply for my projects and circuits as it has useful voltages (12, 5 and 3.3).
Simply with continuity mode of multimeter I checked + and - of power output, then surprisingly I heard the beep sound. However, As I mentioned it has that voltages in the output.

#### Ian0

Joined Aug 7, 2020
10,276
It will beep until your multimeter has charged the output capacitor.

#### WBahn

Joined Mar 31, 2012
30,303
I'm assuming you are measuring the continuity when the supply is powered down? Sure hope so.

Why are you even making this measurement? What is it you are trying to find out?

It's shouldn't come as a surprise that a power supply behaves differently when it is powered up and when it isn't. There can be a number of reasons why it looks like a low resistance at the output when it is powered down. As Ian0 said, one reason is that your meter is having to charge an output capacitor, which might take some time (might even take forever is the leakage current of the capacitor exceeds the continuity test current of your meter).

#### Saeedk9574

Joined Jan 1, 2024
19
I'm assuming you are measuring the continuity when the supply is powered down? Sure hope so.

Why are you even making this measurement? What is it you are trying to find out?

It's shouldn't come as a surprise that a power supply behaves differently when it is powered up and when it isn't. There can be a number of reasons why it looks like a low resistance at the output when it is powered down. As Ian0 said, one reason is that your meter is having to charge an output capacitor, which might take some time (might even take forever is the leakage current of the capacitor exceeds the continuity test current of your meter).
Yes, I have tested continuity when the power supply is off. As I did not hear the beep sound in the another power supply I have, I supposed this one may have problem.
Thank you, I appreciate you. It was really helpful.

#### seanstevens

Joined Sep 22, 2009
258
So when you power up the PC PSU, do you get the right voltages on the outputs as you stated in your first post? I also presumed you must have the enable link in place to get it to output anything without it being in the PC.
If you are getting the right voltages and currents on all the outputs, then I presume it works. Maybe the beep on your meter is caused by something else and is unrelated?
Besides the beep, do you have any other history on the PSU, why is it not in a PC, was it faulty...