"Ok I got the High Voltage Probe and measured the only transistor I could find in the power PCB, the K793 high voltage N-MOSFET with the following results"
Gulp !
The power pcb contains the line voltage power supply. This system, on the primary side of the power transformer has no common electrical relationship to the VDU's secondary power supply system. It is isolated from it by the power transformer by magnetic induction and insulation between the primary and secondary windings, even signals sent back to the primary side, from the secondary side, for feedback control are sent either by transformers or opto-couplers to maintain the isolation.
If you attempt to make a scope measurement on the primary side, with the scope earth clip on common (the chassis or the secondary side) you will just see high voltage 60Hz sine waves. To be able to measure with a scope, on the line side of the power supply where the switching mosfet is, you would require an isolating transformer and a good knowledge and experience of how SMPS supplies work and where to safely clip the scope's earth clip. Luckily, in this case the x100 probe saved the day, if it was just a x10, connected that way, it could have failed & caused problems.
Keep well away from the line side of the power supply.
The place to check the flyback waveform, with the x100 probe, is on the collector of the H output transistor. It would pay to read up on what sort of waveform you would expect to see there, both in the expected amplitude and shape of the wave.