Convergence Update.
I have run the CT100 about 24 hours and the convergence remains very good. It is actually better than the transformer that was in the set before it failed.
The transformer failing first sign was the drifting focus and convergence on warm up. With the convergence pot fixed, the convergence is shows minimal drift from warm up from cold. Also the focus drift is very much reduced.
I used three 10kV .01 uF capacitors in parallel in my final circuit although I earlier used 0.02uF (two in parallel) worked fine.
I also noticed an error in my earlier as built diagram: the 0.018 uF coupling between 12AU7 and IGBT should have read 0.1uF.
With regards to the device I used I was mistaken. It is a 1200 volt IGBT type GF3NC120HD. They are available at Mouser for $1.62 each. (I would be inclined next time to buy 10 for $1.02 each).
https://www.mouser.com/ProductDetail...8Tvd683-o9yPh_
The 0.01uF 10kv capacitors I bought on eBay:
https://www.ebay.com/itm/32496656125...F+10kv&itmmeta
Lastly is attached my most recent as built diagram.