Power supply caps are the most common problem with many brands and models, but with this symptom I would be suspecting something else. Failures on the buffer boards are common in these and can cause this, but there are lots of possibilities. Without some troubleshooting, it is hard to even guess.
Caps are sometimes easy to identify when they are a problem, as they can swell and vent. Other times you need to test them or look at the output of a supply with a scope to identify problems. I suggest starting by just looking to see if you see anything obvious.