Any seasoned techs online? Working on 1980 mercury inline 6 banger?

Question

I am working on a 1980 tower of power while performing dynamic test ie cylinder drop test, I found a no spark situation on# 5. So i hook up my spark tester @ 1.5 inch gap and while CRANKING i observed no spark on only #5. Then #s 1& 3 stoped sparking and i regained spark on #5. I did notice that the upper switch box was controlling #s 1,3, and 5. all stator output to switchbox were in spec.

Answer 1

I've worked on quit a few of those + it sounds to me like a bad upper switch box.

If you have good stator output to the switch box and good trigger output to the switch box then you know it's gonna be that.

Answer 2

If you have the stator volts coming in then check your trigger volts. Should be around 2.5 volts. If you have the volts coming in from trigger then bad switch box. No volts or not enough then bad trigger.