Try what I have cobbled together here in this photo:
3 wires to check from the MercOtronic.
small red
small black
large red(primary)
Try connecting them as I have marked on this photo.
The glob of solder is, or if memory serves, from the old condenser??? Mine was rectangular and had same globs on it, connect the small red lead from the tester to that one.
small black to location noted on picture.
And large red from tester to spot marked as such.
The spot is right where I got spark on my 1914 coil, I surmise it was to have had a tab to attach the plug lead going down to the plug. Mine was missing but that is where I got spark.
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