MH596 is a Dell proprietary 280W Power Supply for Optiplex GX520 GX620 DT 745 755.  It is not recommended in this community to buy replacement proprietary psu for this 15 year old 2007 pc model, unless you can find a free working unit from e-recycle.  This psu can not be used in any newer Dell desktop pc model.  Some people like to tinker with old tech and do not mind spending a little money on it.  If that is you, understand.  H280P-01 works too Dell 280 Watt Power Supply for Dell Dimension and Optiplex Computers. Dell P/N NH429. [IMAGE] [IMAGE]    
HI,   Yes I have read all the others who have had similar probs but thought I'd run it by here, before I went and got a new supply. I have a new lith battery, cleaned mobo taken out and replaced RAM, disconnected all cables. Power switch on and I see the PSU fan goes on then stops, light still flashes.   Takes me 3 secs or so to hold so it turns off. Does this sound like PSU. Thanks oz    
Old Dell 755 amber power light flashing