Did you check Q603? It may be bad. There also a diode near it that is possibly the problem. They put those diodes right near those big white power resistors, and they end up failing on a lot of boards I repair, due to taking the heat.
Also, when I replace the diodes, I mount them on the solder side of the board, to get them away from the heat.
Personally I wouldn't use a half watt there. Technically it will work, but if something in that circuit shorts (like Q603), you're going to have a bigger fireball on your hands, before it burns up and goes open.