The most likely cause is the Laser Scanner Unit (LSU). They cannot usually be repaired, parts are impossible to find. Unfortunately there is no real alternative to replacing the LSU, if that does not fix the problem the next most likely cause is the Main Board. Both are expensive so you might want to see how the cost of the LSU compares to a replacement printer. You could google for a Samsung ML-2010 Laser Scanner Unit to compare prices. Alternatively get a quote from a repair shop and compare that with buying the LSU yourself.
Answers & Comments
The most likely cause is the Laser Scanner Unit (LSU). They cannot
usually be repaired, parts are impossible to find. Unfortunately there
is no real alternative to replacing the LSU, if that does not fix the
problem the next most likely cause is the Main Board. Both are
expensive so you might want to see how the cost of the LSU compares to
a replacement printer. You could google for a Samsung ML-2010 Laser
Scanner Unit to compare prices.
Alternatively get a quote from a repair shop and compare that with
buying the LSU yourself.