How did you go with the repair ?
Often, with these power supply boards I would just replace all the output electrolytic capacitors with "quality" low ESR types. The output capacitors are heated internally by ripple current, some significantly. Any warm/hot diodes close by will add to that heat stress. Generally the low volt ones fail first or near a hot diode, sometimes visually evident. Check the old ones for confirmation.
The " dark spot" around IC901 is overheat of the pcb, it is quite common in consumer equipment power supplies, you might see it near some diodes as well. It is due to less than good thermal design for the ambient operating temperature, & is made worse by leaving unit on 24/7.
If you get it running again, stick on a small ceramic heatsink (DON'T use metal !), this should help IC901 heat dissipation.
Hopefully you should get another 5 years use.
cheers
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Ceramic heatsinks