I'm trying to track down the cause of a "stuck on" buzzer circuit in my Big League Bulls Eye PNB. I've managed to work through all the machines issue except this one and need some help.

The buzzer is supposed to buzz after the third out for both player one and two. It does this via a "third out relay" and a switch on the score motor. When both of these switches are closed the buzzer is supposed to be grounded and "buzz". The problem is 24 volts of AC power constantly goes through the buzzer circuit even when the switches are in the normally open position. I suspect a short somewhere in the relay/switch controlled ground circuit. But am getting some very strange readings from my multi-meter.

With the machine off, I've run continuity tests across the relay and switch all the way to the buzzer and they are working as designed. When both switches are closed I can trace continuity from the score motor all the way to the buzzer, when the switches are open there is no continuity.

When I measure voltage, across the jones plug for the buzzer I get 24 volts when the machine is on and I've got a leads hooked up to both side of the buzzer's jones plug. The voltage should be zero until the buzzer relay and score motor switch complete the circuit.

Where this gets strange is if I remove the multi-meter lead on the switched side of the jones plug and leave a single lead from the multi-meter connected to the powered side of the jones plug I measure 4V AC. How is the ground being completed for the circuit? I'm not sure if this has anything to do with my short issue, but thought it would be nice to at least understand before moving forward with my tracing.

Anybody seen one of these mysterious single lead AC voltages before?

TIA

Allen