Modded atx PSU issue

Thread Starter

Nikola Zlatkov

Joined Aug 22, 2017
12
I just made my first electronics project, a modded atx psu into a lab bench test psu. And I ran into an issue. First of all when i plug my psu the red led doesn't light up which it should. When I flip the switch the green led turns on and the fan. When I measure voltages with my multimeter everything is fine, but when i plug my fan in the 12v socket the psu turns off. And later I found out that the psu turns off by itself after 20 seconds with no additional load. Can someone provide me the answer?
 

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Dodgydave

Joined Jun 22, 2012
10,063
You should have 5v on the purple standby continuously, you don't need the Grey wire, to put the psu on short the Green to Black, 12V on the Yellows, 5V on the Reds, your 5 ohms load resistor should be on the Reds to Blacks.


If it's shutting down, try another load resistor on the Yellows of 5 ohms...
 

Thread Starter

Nikola Zlatkov

Joined Aug 22, 2017
12
You should have 5v on the purple standby continuously, you don't need the Grey wire, to put the psu on short the Green to Black, 12V on the Yellows, 5V on the Reds, your 5 ohms load resistor should be on the Reds to Blacks.


If it's shutting down, try another load resistor on the Yellows of 5 ohms...
So you're suggesting that I disconnect the grey wire, first and if it still doesn't run properly try to put a resistor on the 12v rail instead of the 5v rail?
 

MrAl

Joined Jun 17, 2014
8,503
Hi,

Many power supplies need a resistance on the 5v line. It varies what it might have to be though, like 5 ohms or 10 ohms, and it has to be a power resistor that can handle the power.
 
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