Converting a monitor from 625 to 405

[Murphyv310]

Cramping and or RH foldover seems to be the norm when you go down in frequency. It could be S correction related but I've found its a mismatch between the scan coils and line transformer. Using a Thorn jellypots 625 scan coil drive connections to feed on 405 gives this severe non linearity, reverting to the 405 connections gives perfect results.
I'm watching this with interest.
Good work so far.