[Irinikus]

If the design is anything like the FW900 and other late Sony displays, there is a separate transistor for the horizontal drive (which goes to the yoke) and the HV oscillator (which goes to the flyback transformer).
In the FW900 schematic, those are Q515 (a 2SC5570) and Q901/Q906 (two 2SK2655's) respectively. The H Drive transistor is on the long heatsink along the edge of the board, while the HV FETs are near the FBT (which is opposite to the long heatsink), and have their own small heatsinks.

This board doesn't have those numbers, however I think I've pictured the two transistors. The one in the centre of the heatsink has two high power diodes mounted next to it (If that helps in any way) and it's also closer to the coupling that goes to the yoke.

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Here are the specs of the transistor they sold me with the flyback:



These are the specs of the pictured transistor: