Sudden stall on XJ6 then no spark

[Doug_Dwyer (Doug Dwyer 1985 Series III V12)]

There is info in this thread that might be useful

Series 3 ignition

Is there a way of testing the ignition amplifier and what resistance should the ballast resister have .i have chopped and changed coils and at my wits end to sort out my ignition . I have a yellow spark at the coil and at the plugs

Cheers
DD