I wonder if it is possible that somebody put a TS-15 mag plate on your TS-20? TS-15 had maverick spark suppressors, TS-20 did not. It makes a big difference in how you test the coils. Connect your meter leads to the spark wire solder connection and the terminal of the ground wire at the armature plate, NOT to the plate itself. Connecting them correctly takes the spark suppressors out of the picture (if it has spark suppressors).
