MPU 1000 Antenna

[darwinasm86]

Anyone know why and what the Antenna is used for on this Mother Board?

[rokgpsman]

I believe it was added as a security device by the Bally engineers. If you trace it out the antenna is simply a circuit trace that goes around one of the display boards and then back to the mpu. If it picks up enough rf signal it will shut down the mpu. Back in those days they worried about someone trying to cheat and confuse the machine by using a small handheld battery operated rf signal generator, sort of like a little jammer. Some people were caught with these things and Bally responded. As far as I know I don't think anyone was ever actually able to cause a machine to payout when it wasn't supposed to using them, but the worry was there in the early days of electronic slot machines. Back then people were a little paranoid about what all was possible to hack the slot machine and cheat the casino. Magazines like Popular Mechanics and Popular Science were always having ads and stories about little electronic devices you could build. If that cheating method actually worked you'd see an antenna circuit like this on every slot machine made today - but it isn't.

[dhellis]

The antenna is on J1 pin 11 and is used in a circuit described as 'Static Detect'
which is mostly consistent of the 555 timer and one of the transistors in the transistor array IC.
When static is detected it will force a reset on the machine.

I agree with rokgpsman, that it was a security device aimed at preventing cheating.

[ramegoom]

Might almost make sense to remove the 555 chip and associated components for your home machine. One less reason for a bad component to set a tilt code. I believe I have left the 555 out of my CPU completely and the machine still worked normally.

Seems that location on the CPU tends to collect corrosion under the chip. I have seen that on a few machines so far. Must be near a water trap.