Computer Power Supply Tester – Electronics Projects Circuits

The ATX power supply tester I made years ago, there was no such tester in our market at that time. Purchased power supplies were generally tested by short-circuiting the green and black cable, the fan turned, the output voltages were sufficient if they were normal, but when they were plugged into the motherboard, malfunctions occurred or the repaired power supplies were causing problems on the motherboard. I also designed a simple test card, I’ve been using it for about 20 years, thousands of power supplies have been tested with this card.

ATX Test Circuit Detailed Description;

I changed the resistors I used for the ATX PSU test circuit according to my experience and found the most suitable values. At first, I chose the resistor values very low on the 3.3V, 5V, 12V lines, but some power supplies were switching to protection, then I increased the resistance values and found the appropriate values by trying. There were such strange malfunctions, for example, when I connected the test device, the ATX power supply was going to protect, it was very difficult.

I found that the -12V rectifier diode was faulty, and the solution was instant on the test card – I wonder if the -12v led went out very quickly, I wondered if the continuation came 🙂 although it is already connected to the load resistor, it is normal for it to go out quickly. No matter how I looked, I saw a difference, moreover, there were about 200 accumulated power supplies from the same failure, all the same failure, I was very surprised, I think there was a production-related problem with the diodes..

In fact, from those years to this day, the power supplies are much more powerful, the value of the 5W resistors can be reduced a little more, but there was no need, anyway, according to the repair you usually do, there is no need for a high power test.

ATX power supply test circuit is not designed for performance testing anyway, very detailed design is required for this job, you can only use it to test the power supply on light load. The card draws approximately 3.5A in total, if you are dealing with high-power devices, calculate the resistance; V / R ie voltage divided by resistance for example 5 volts 5/3.9 = 1.2(A)

There was no power supply that worked on this card and did not work in the case, causing problems. LED is used for voltage indication, multimeter is required for voltage measurement. At first, I was going to add a voltmeter commutator and further develop the circuit. There was no time anyway.

Note: Sometimes, when you connect the power supplies with swelling capacitors to the test circuit, the problem becomes clear, but it does not switch to protection, depending on the state of the swelling capacitors in general.

In fact, if it is connected to the circuit for a long time, it will protect, but there is no need to wait, turn on the device and check the capacitors.

I made the PCB design of the ATX Power supply test board single-layer, but since I ordered PCB from China, I designed a double-layer PCB to provide better cooling, but it will be difficult to solder to the chassis line with a 30w soldering iron, you can easily solder it by preheating it with a high-power soldering iron or dryer. I used a 60w soldering iron. PCB design was prepared with sprint layout 6

Finally, there were -12V and -5V in the old ATX power supplies, then -5V was removed.

Computer PSU Tester Circuit Diagram