From: nospam@needed.invalid   
      
   On Fri, 7/18/2025 9:16 AM, Felix wrote:   
   > Edmund wrote:   
   >> On 7/16/25 16:50, pinnerite wrote:   
   >>> I connected a brand new Asus Tuf 850W PSU to an ASUS motherboard with   
   >>> just the processor and heatsink installed, in a MIDI Tower case.   
   >>>   
   >>> The PSU was not in the case.   
   >>>   
   >>> Switched on and...   
   >>>   
   >>> Nothing happened.   
   >>>   
   >>> I detached the PSU and attached a small tester to it.   
   >>> Powered on ...   
   >>>   
   >>> No sign of life.   
   >>>   
   >>> What can cause a PSU to die under those conditions?   
   >>> Surely it has inbuilt protection against overload.   
   >>>   
   >>>   
   >>>   
   >>>   
   >> What comes to mind is, it didn't die but doesn't switch on.   
   >> There might be a electrical check that isn't happy.   
   >> Are you sure you connected all plugs and cables to the mainboard?   
   >>   
   >> As usual, if everything else fails, read the manual.   
   >>   
   >>   
   >   
   > also did he connect the CPU 12v power, and the case switch cable to   
   motherboard power switch pins?   
      
   He has built systems before.   
      
   He is looking for some encouragement.   
      
   1) He had a working system.   
   2) The power supply in the working system, stopped working.   
   3) A replacement supply is also not working and is not   
      responding to PS_ON# testing. He tests the supplies before   
      inserting them into a computer case. The tester is likely   
      a window comparator type, which tells you whether all rails   
      are within acceptable voltage.   
      
   These are autoswitching supplies, the OP is in the UK and   
   the supply would be assuming a 240V input (50Hz).   
      
   As is standard for UK people, he would have checked the fuse on the cord   
   fitted to the supply. The fuse has to be able to withstand   
   the inrush of the supply, when the supply is switched on at   
   the back of the unit. The internal safety Slo Blow fuse,   
   easily withstands the inrush current.   
      
   A Kill-A-Watt meter, can be used to detect power draw, as   
   a "sign of life" from the unit.   
      
   Overloading the +5VSB, could shut off that output, but it   
   might be self-restoring rather than being a latch-off circuit.   
   Some of the +5VSB supplies use switchers now, and the   
   little switcher is not power factor corrected, so the   
   reactive component seems rather high when you measure it.   
      
   There is no particular advantage to connecting the PSU to   
   the motherboard, until the question of whether the supply   
   actually works is resolved. If the supply is good, it should   
   be able to pass a test, outside of the computer case. All   
   it takes, for example, is a PSU tester that operated   
   PS_ON# properly and has the 24 pin pinout of an ATX when   
   it measures the voltages.   
      
      Paul   
      
   --- SoupGate-Win32 v1.05   
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