Working on my first em Bally boomerang. Fixed several problems but a new one popped up. Bonus countdown and scoring was working properly now its not.
Heres whats happening.
During play everything advances fine bonus lights go up normal. Ball drains and the bonus advance goes up one and kicks the ball out for next ball no score. Bonus count doesnt reset.
The bonus advancing one after drain is weird. The bonus "0" relay looks toasty it is at 49 ohms it is rated at 78 should I just change it out?
That relay doesnt seem to be doing anything. Its tuff to get to in the back of the box. The schematic says the bonus unit zero switch is closed to trigger it. Is that on the bonus stepper unit?
Part of this circuit is the ball index hold relay which seems to working normal. I checked relevant score motor switches but didnt clean any contacts yet. I dont want to just start filing with a bunch of contacts unless I have to. Dont want to cause more problems
Also if I manually trigger the bonus score relay it does count down bonus as normal of course no score. Must be bonus zero relay right?

Sorry if any questions are obvious or dumb. Just starting really and schematics are kind of crazy but im getting better.
Thanks for any help

i have also read clays guides multiple times.

It doesnt countdown when the ball is in the outhole but it counts up one. Which I cant wrap my head around ,the only things I see in common with the step up solenoid and the step down are the outhole switch/relay and the bonus zero relay.
I will look at the game later and see if the bonus score relay is triggering when ball is in outhole. I think the score motor is only turning one time also when the ball is in the outhole.

If I hold down the outhole switch after scoring a bit the score motor continues to turn and the stepper unit continues to count up. If I hold in the bonus zero relay and trip the outhole switch it counts down and scores as normal. I t is also going up one bonus point when the ball kicks out the outhole.

Thanks Tim, Your explanation is making sense to me. I believe the bonus stepper zero switch does open at zero ,but I will check tomorrow. I did order another coil for bonus zero relay ( it was low resistance in circuit and black wrapper and burnt looking coil lug plastic part) I will post my results after that.

Got it! Im dumb, checking switches everywhere. It was a cold solder joint on the bonus stepper zero switch. I did change out the bonus zero relay because it was on its way out anyway. Thanks alot!