Pc starts but no picture since I changed heat sink

[StuDoog]

Monitor has no picture since I replaced heat sink. I have checked all relevant forums. There is no damage on mobo or processor

 

[Falkentyne]

This isn't a monitor issue. Post this in the CPU forums.
Do you get a "beep" when you turn on the computer? Does windows actually start loading? Is there hard disk activity (is the HDD light blinking a lot or is it solid red?) Do the keyboard caps/num lock/scroll lock respond ?

IF the PC is actually active and booting to windows and there is actual drive activity (not just a solid red frozen light or HDD LED) and you got a POST Beep (power on self test beep) but nothing on the monitor, this is usually caused by video card cables or PCIE cables or auxiliary pcie cables (if the motherboard has them) being unplugged.

If PC is completely frozen (no beeps, non responsive caps lock, HDD light frozen hard, no drive activity) then usually the cause is:
1) CPU mounting error.
2) Bent CPU / motherboard pins
3) improperly inserted video card.
4) PCIE power connector not plugged in
5) ATX12V 24 pin power connector not plugged in (if this is unplugged, however, there will be NO power to anything, nothing, no lights)
6) CPU 12v power plug unplugged (people forgetting to plug this in happens far more than you think).
7) BIOS corruption (try the clear cmos button?)
8) too much pressure on CPU socket/bad heatsink mounting (motherboard warping can prevent power on POST).