That's it. Nothing on the display, no beeps.
The radiator of bottom CPU doesn't heat after switching power on we have noticed, the top one is warm.
We have read the spec and according table 62 on page 151 it is 28h code. Memory? We replaced memory strips, didn't help.
These diagnostic lights are intended to debug the unit when it is not completing its POST sequence. Once the unit has booted up, there is no actual meaning of these lights.
You can use the following document for more information about the meaning of the lights.
http://www.intel.com/content/www/us/en/support/boards-and-kits/000006711.html SE7520BD2 Technical Product Specifications