ATX stby voltage too low +1.8v

[kamel]

hi!
Got fuj. siemens esprimo c5910 with power issue : no reaction to switch.

To make pc start, need to power up PSU alone without load (by grounding pson) before connecting it to mobo

All PSU voltages are checked ok without load (stby voltage=+5v), but when connected to mobo, stby voltage becomes low : 1.8V.

Steps taken : swapped PSU with a good working one, pc starts normally.

Concluded that PSU is culprit, and particularly stby rail.

Opened PSU case, all caps are looking fine.

Any idea as what are the main stby rail check points and where to dig further to help fixing this issue ?

Thank you

[SteveNielsen]

Re: ATX stby voltage too low +1.8v

Post the make and model of the psu and good pics of the psu guts, top and bottom of the board. then someone may be able to help ts it.

[CapLeaker]

Re: ATX stby voltage too low +1.8v

Any hi res pictures from top and bottom to go with this? I think that this is a "special" PSU as it is rectangular tube shaped and does not use a standard ATX PSU case.

[kamel]

Re: ATX stby voltage too low +1.8v

hi,

PSU model : NEWTON POWER LTD MODEL : NPS-210BB A REV : 08 -210W

Unfortunately, no specific schematic found on the net.

Here attached some photos.

[kamel]

Re: ATX stby voltage too low +1.8v

Here newly attached reduced size photos, if previous photos are slow to load.

[stj]

Re: ATX stby voltage too low +1.8v

probably bad caps on the standby causing voltdrop when there is actually a load.
specially in that, it's packed like a train during rush-hour!

[kamel]

Re: ATX stby voltage too low +1.8v

Sorry Board1 and 2 uploaded were same.

Here attached real Board2 of PSU.

[kamel]

Re: ATX stby voltage too low +1.8v

probably bad caps on the standby causing voltdrop when there is actually a load.
specially in that, it's packed like a train during rush-hour!

Caps are looking quite fine. If no other fix found, will change all caps on stby rail.

[CapLeaker]

Re: ATX stby voltage too low +1.8v

x2 what stj said.

[momaka]

Re: ATX stby voltage too low +1.8v

Caps are looking quite fine. If no other fix found, will change all caps on stby rail.

They can look "fine" but still be bad. Without an ESR meter, you can't really know for sure.
So in cases like yours, it is best to change them. I've seen bad caps (that looked physically good) make the 5 VSB act weird in more than one occasion.

[nimit]

ATX stby work proper but no output

i have i ball xpx-252 psu in which i get standby voltage perfectly, & also get power on volt but i cant get final output of 5,12,3.3 etc
i have checked al componant all is well. i have found that power transformer not get voltage in it's primer nor secondary , i dont know how to check drive pulse in circuit.
please guide me.
i am beginner.

[momaka]

Re: ATX stby voltage too low +1.8v

@ nimit: start a new thread and post some pictures of your power supply there.