The Add Bonus Unit solenoid fires at two different speeds depending on which circuit path (upper or lower) is being used:
Big Shot bonus (resized).jpg
Not knowing how many targets are lit, the Bonus Unit must examine all 15 targets one at a time and add points for those that are lit.
When the ball drains, the C/Add Bonus Unit relay (not shown) fires which starts up the Score Motor. With the Score Motor turning, the Score Motor Switch at position 1A generates groups of 5 pulses for every 120 degree turn of the lower Score Motor cam. Those pulses go along the upper path through the (now closed) C relay switch, the Normally Closed J relay switch and the Make/Break I relay switch and advance the Bonus Unit 5 steps per 120 degrees turn of the Score Motor Cam.
When the Bonus Unit steps to a position where the target is lit (refer to the schematic in reply #4) the uncommon, 6 volt J/Bonus Score Control relay fires which immediately opens the Normally Closed J relay switch, so no more pulses (in groups of 5) can get to the Add Bonus Unit solenoid through the upper path. The J relay also fires the I/Bonus Score relay (when the switch at Score Motor position 2B closes) which throws the I relay Make/Break switch into the opposite position. With the I relay Make/Break switch in this new position the 5 pulses from the Score Motor 1A switch must go through the lower path where the Normally Open Score Motor 1B switch only allows one of the 5 pulses through. That's what slows down the Bonus Unit when points needs to be added.
The I relay holds for nearly an entire 120 degree score motor turn, while 1, 2 or 3000 points are added for the lit target and the Add Bonus Unit is advanced one step, until the Normally Closed Score Motor 3C switch opens at the end of the cycle. Then it relaxes, the Make/Break switch flips back again and the 5 pulses are allowed once again to advance the Bonus Unit until the next lit target is found.
It's a really neat design that quickly skips over the unlit targets and slows down to allow for a variable number of points to be added for each lit target.
Quoted from bonzo71:
I gapped the switch with the white/maroon white was wide as possible and this fixed the issue.
I'm pleasantly surprised to hear that. I didn't think that was the most likely cause.