Low green wire voltage 3.3v ps-on power atx

[electronium]

Hello friends of the forum
I have an atx power supply that has standby voltage conditions. The voltage of the purple wire is 5 volts and the voltage of the green wire ps-on is 3.3 volts and the power switch does not start. What is the problem and where is it ?

 

[JimB]

Sorry Electronium, many of us here speak a range of languages, but I am sure that very few speak Persian.

Using Google Translate, I get this:

Hello friends of the forum
I have an atx power supply that is ready for voltage conditions. The voltage of the purple wire is 5 volts and the voltage of the green wire ps-on is 3.3 volts and the power switch does not start. What is the problem and where is it ?: meh:

Welcome to the forum.

JimB

 

[Reloadron]

Translation:
Hello friends of the forum
I have an atx power supply that is ready for voltage conditions. The voltage of the purple wire is 5 volts and the voltage of the green wire ps-on is 3.3 volts and the power switch does not start. What is the problem and where is it ?: meh:

ATX PSU pinout. Green is PS_ON and should be 5.0 volts, grounding the Green should force the PSU to start. Purple is 5.0 volt SB (Stand By). You should be seeing 5.0 volts on the green held up by a pullup.

Ron

 

[electronium]

Sorry Electronium, many of us here speak a range of languages, but I am sure that very few speak Persian.

Using Google Translate, I get this:


Welcome to the forum.

JimB

Hello friends of the forum
I have an atx power supply that has standby voltage conditions. The voltage of the purple wire is 5 volts and the voltage of the green wire ps-on is 3.3 volts and the power switch does not start. What is the problem and where is it ?: meh:

 

[electronium]

Translation:
Hello friends of the forum
I have an atx power supply that is ready for voltage conditions. The voltage of the purple wire is 5 volts and the voltage of the green wire ps-on is 3.3 volts and the power switch does not start. What is the problem and where is it ?: meh:

ATX PSU pinout. Green is PS_ON and should be 5.0 volts, grounding the Green should force the PSU to start. Purple is 5.0 volt SB (Stand By). You should be seeing 5.0 volts on the green held up by a pullup.

Ron

The voltage of the green wire is low, I do not know which part to check, as if all the parts are healthy ... and I connect the green wire to the chassis, nothing happens

 

[Reloadron]

The voltage of the green wire is low, I do not know which part to check, as if all the parts are healthy ... and I connect the green wire to the chassis, nothing happens

I assume the PSU is removed from the PC. The voltage on the PS_ON should be the same as the 5.0 volt standby voltage. The PS_ON line is held logic high as a result of an internal pullup resistor. Pulling PS_ON low to ground starts the power supply. Logic low is any of the black wires which are ground. Any voltage measurements should be referenced to ground. Some PSUs when started stand alone need an external load but I haven't seen a need for that in years and it depends on the PSU.

Normally when an ATX PSU fails it is just replaced. Finding a decent schematic and anything beyond some very basic troubleshooting is not an easy task.

Ron

 

[electronium]

I assume the PSU is removed from the PC. The voltage on the PS_ON should be the same as the 5.0 volt standby voltage. The PS_ON line is held logic high as a result of an internal pullup resistor. Pulling PS_ON low to ground starts the power supply. Logic low is any of the black wires which are ground. Any voltage measurements should be referenced to ground. Some PSUs when started stand alone need an external load but I haven't seen a need for that in years and it depends on the PSU.

Normally when an ATX PSU fails it is just replaced. Finding a decent schematic and anything beyond some very basic troubleshooting is not an easy task.

Ron

I assume the PSU is removed from the PC. The voltage on the PS_ON should be the same as the 5.0 volt standby voltage. The PS_ON line is held logic high as a result of an internal pullup resistor. Pulling PS_ON low to ground starts the power supply. Logic low is any of the black wires which are ground. Any voltage measurements should be referenced to ground. Some PSUs when started stand alone need an external load but I haven't seen a need for that in years and it depends on the PSU.

Normally when an ATX PSU fails it is just replaced. Finding a decent schematic and anything beyond some very basic troubleshooting is not an easy task.

Ron

I got the voltage. The next resistor of the ps -on pin was 5 volts, and the same path went to the 3 IC lm339 pin and at the same time to the 4.7uf 50v capacitor. It does not work and I do not have line voltages 5, 12, 3.3 and -12

 

[alec_t]

Welcome to ETO!
What are the markings on the two ICs?

 

[electronium]

Welcome to ETO!
What are the markings on the two ICs?

The path characteristic is equal to 5 volts

 

[alec_t]

So it may be, but that doesn't answer my question. What type numbers are on the ICs (the pics are not in sharp focus)?

 

[electronium]

So it may be, but that doesn't answer my question. What type numbers are on the ICs (the pics are not in sharp focus)?

ic lm339
ic tl494

 

[alec_t]

Thank you.
This site has schematics for various ATX supplies using the TL494. If you spot one which corresponds to the manufacturer of your ATX, that would be a good start to help fault diagnosis.

 

[electronium]

Thank you.
This site has schematics for various ATX supplies using the TL494. If you spot one which corresponds to the manufacturer of your ATX, that would be a good start to help fault diagnosis.

Surprisingly, the parameters of the tl494 IC are correct and indicate that the tl494 IC is sound, and that the lm339 IC also measures the voltage of the corresponding base values and the accuracy of the characteristics is OK.

 

[alec_t]

Are you saying that all the voltages are being generated correctly, but just not reaching the output terminals of the supply?