Converting a monitor from 625 to 405

[ppppenguin]

The circuit diagram for these monitors is very badly drafted. Makes it hard to understand how it really works. Fortunately there's a pretty good description in the manual. From memory, the H sync flywheel is quite complex but at heart it's an RC oscillator that will inherently have a wide pull-in range. Frame timebases tend to be fairly unfussy about whether they run at 50Hz or 60Hz though the height may change.