Really hard problem, no one could help me so far!

[Legacy_DMC]

Hello, good night.

Im building a Simple office pc with an

Athlon 200GE
4Gb DDR4 Ram
Biostar A320MH

The problem is, that all the pc components are working properly, with the exception of the psu, which is a Delta DPS-300AB-9, a 300w With active PFC PSU The motherboard works with another psu, and the psu works with another motherboard, but both don't work together

What could be the problem?
(if i let the psu plugged into the motherboard and turn it on, even though nothing spins, the chipset starts getting warm after some time, is this a good thing?)

(Edit 1)
More details, with the old psu, it works fine. so the motherboard and all other components are good, as for the psu, it also works fine when connected with another motherboard, tested all rails, and all are bringing the voltage that they were suposed to

(Edit 2)
The chipset got warm only once, then, i couldn't do it again with the new psu, using the old one everything works fine. I've made sure the new psu is 100% ok, measured every single line, and all voltages are correct.
the motherboard is also working perfectly            

 

(Edit 3)

When i short the two power pins on the motherboard, the psu just doesn't start even though, neither the psu, or the motherboard are with problems.

[mariushm]

Open the power supply and visually inspect the electrolytic capacitors, especially the 5v standby capacitor.

The chipset is powered by the 5v standby circuit, which can become unstable if the capacitor is degraded. You can measure 5v with no load, but when the motherboard starts and the chipset draws 0.5-1A from 5v standby, the circuit could become unstable and the voltage could wildly oscillate between something like 3v and 5v.

 

I think this is the picture of internals of that Delta psu ... the capacitor would be somewhere under that bundle of wires, close to a pink/purple wire ... look at the 24pin pinout and follow that 5v standby wire to where it goes in the circuit board.

It's usually 1500uF...2200uF 6.3v..10v rated electrolytic capacitor.

 

If it's swollen or not looking good, that's your problem.

 

 

 

[Chaftalie]

If you open the PSU (what I cannot recommend if you do not have any electrical background)
do NOT touch any exposed metals. do NOT touch the underside of the PCB, the caps can still be charged with mains voltage

and touching that can be lethal!

[mariushm]

You CAN open the power supply.  Most cases are designed in such a way that the top cover lifts up, so you don't have to touch the insides to remove the top.

 

All power supplies are pretty much split into a HOT (high voltage side) and a low voltage side, where all voltages are small so the risk of electrocution is pretty much none, making it safe to touch

The heatsinks are USUALLY connected to earth, but it's not a rule, and if a mosfet or transistor on the primary side explodes it's possible for that heatsink to become live. As the power supply seems to work, that's not the case here.

Also, it's a common practice to have a discharge circuit to discharge high voltage capacitors. Once a power supply is turned off, that big primary capacitor should discharge to safe voltages within 10-30s. Still just in case that circuit is not working or there's no such circuit it's best not to put your fingers under that capacitor, basically don't touch the leads of that big cap.

 

So in the picture below, you can lift the metal lid off the case and then touching ONLY the wires you can gently pull on them and bend them so that they go over the secondary heatsink, and you'll see the capacitors that the cables cover and the capacitors on that control circuit board.

Just look if their tops are swollen or if they leak (you would see something that looks like rust or liquid

 

Here's a couple examples of how they should not look

 

 

 

Here's the delta psu 

 

[Legacy_DMC]

9 hours ago, Chaftalie said:

If you open the PSU (what I cannot recommend if you do not have any electrical background)
do NOT touch any exposed metals. do NOT touch the underside of the PCB, the caps can still be charged with mains voltage

and touching that can be lethal!

I Do actually know eletronics, and yeah, after checking every single capacitor, all of them are good, and normal, no leaks, nothing.

[Legacy_DMC]

2 hours ago, mariushm said:

You CAN open the power supply.  Most cases are designed in such a way that the top cover lifts up, so you don't have to touch the insides to remove the top.

 

All power supplies are pretty much split into a HOT (high voltage side) and a low voltage side, where all voltages are small so the risk of electrocution is pretty much none, making it safe to touch

The heatsinks are USUALLY connected to earth, but it's not a rule, and if a mosfet or transistor on the primary side explodes it's possible for that heatsink to become live. As the power supply seems to work, that's not the case here.

Also, it's a common practice to have a discharge circuit to discharge high voltage capacitors. Once a power supply is turned off, that big primary capacitor should discharge to safe voltages within 10-30s. Still just in case that circuit is not working or there's no such circuit it's best not to put your fingers under that capacitor, basically don't touch the leads of that big cap.

 

So in the picture below, you can lift the metal lid off the case and then touching ONLY the wires you can gently pull on them and bend them so that they go over the secondary heatsink, and you'll see the capacitors that the cables cover and the capacitors on that control circuit board.

Just look if their tops are swollen or if they leak (you would see something that looks like rust or liquid

 

Here's a couple examples of how they should not look

 

 

 

Here's the delta psu 

 

everything seens to be working good, and properly inside the psu, the problem is that This specific psu, doesn't work with my specific motherboard (this combo) even though, both are 100% compatible and are 100% healthy

[Legacy_DMC]

any hint?

 

[Legacy_DMC]

well, bought another of the same psu, if it's my unit with a problem, we will know soon