I have found what values should be used for R168 (390 Ohms) & ZD102 (18V 500mW).The problem now is to find an equivalent for the now obsolete Fuji Electric IGBT, Part No.1MI100H-025.
I can not find any data on the device, including Fuji and their distributors web sites.
If any one has data on this IGBT I can be contacted on jhorsley at ukf dot net
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