Display screen late coming on

Not knowing the model, I can only take an educated guess on this one...

Many of the Sony systems have LED or LCD displays on the front with multiple pins that protrude through the front PC board. Look at each end of a long series of pins which should be the display connections. There are likely poor solder connections at these ends. For completeness, resolder each of the pins, re-assemble the unit and try it out. I expect this to resolve the problem.

What is happening is that the heat from the running amp is making the connections swell slightly making contact which then allows it to work as expected.

Dan