I have used my Optiplex 7010 sff for 5 years.  It worked very well before. But today when I wanted to boot it, the computer cannot boot into system. Instead amber led blinks every about 5 seconds.  I cannot find this kind of status in this computer's diagnose manual and https://www.dell.com/support/manuals/zh-cn/optiplex-7010/opti7010_usff/power-led-diagnostics?guid=guid-52106768-c0ec-411e-a583-375a950df672 this webpage.  I have  taken down the DDR memory, harddisk , GPU, usb devices  to diagnose it , this phenomenon sometimes still happen, sometimes amber led show "no memory modules are detected".  Then I plug in memory and other devices, sometimes it can boot into windows, more often it still amber led blinks every about 5 seconds. Do you know what does "amber led blinks every about 5 seconds" mean?  which part of my computer have problem, power supply or motherboad? Thanks.