screen goes black randomly on sony trinitron?

PS. In your case sounds like the first dry joints to check is to the tube heater supply.

Cobweb
September 2005

Very commonly suffer from multiple dry soldered joints.
To access them all, the main board needs to be removed from the plastic chassis and checked all over.
Also, need to check the Tuner & I.F. board for same.
Should be carried out only by a qualified engineer as it involves a fair bit of disturbance to the TV, removal of plug/socket connections and wire looms. Done loads of them and takes about an hour to complete properly.

Cobweb
September 2005