The GDM-5010PT and GDM-500PS are both Sony N3 chassis. Far and away the most common failure is IC007 CXA2043Q, which can result in many types of problems. Search this group, as well as
http://www.anatekcorp.com/faq/monitor.htm and the sci.electronics.repair archives
http://groups.google.com/advanced_group_search for CXA2043Q, and you will gets lots of hits/info.