I offered to have a look at a friends digital TV set top box that was faulty. It was a Dick Smith branded unit (G7659?) that appears to be a DTR7100 made by Pacific Satellite.
A web search suggested that there were problems with the power supply. I ignored this information at first. Instead I noticed that the power supply voltages were printed on the main board. I checked them to find that they were all working, but not quite close enough to the stated voltage. I then examined the power supply board more carefully. I noticed 3 failed capacitors next to a heat sink. I could tell that they were faulty because their tops were domed rather than flat.
I replaced them and the box now works fine.