> Could someone please clarify if IC1 is the +5 voltage regulator and if
> it s possible that this part is defective
It is possible, but also a defect the switching powersupply for the -10V
voltage might be broken and it would pull down the voltage that feeds
also the 7805.
You'd have to unsolder Q1 and Q2 to remove their influence.
Then you can judge, whether the 7805 is broken.