Bally 5500 comm problem

[ChizzleMonkey]

I've noticed a lot of these Bally 5500's with failing bill validators. Replace the bill validator with a know good one and the problem still exists. A good fix that I've found is the DUART chip. It's on the mpu. DUART is Dual Asynchronous Recieve and Transmit. Makes sense on the part of communications.

[garymunson]

What type failures are you referring to? My DBV just refuses to pull a bill in. The green 'entry slot light' goes on when you should be putting in a bill but the little motor just does not start up to pull the bill in. Am I correct that the light going on and off confirms the communication with the game is good? I am under the impression that as long as that light is on, the DBV should be in 'run' mode, pull the bill in, and if valid, pass the denomination info to the game. Since my DBV goes through it's 'dance' upon power up (including running the motor in reverse to clear any bill in the validator), I'm guessing the DBV processor is functioning and that my problem is most likely the failure of the DBV circuit that 'looks' for a bill being inserted in the DBV and that the green light going on and off at the appropriate time indicates the two devices are talking. The game doesn't really have anything to do with starting the DBV motor other than sending the signal that it's ready for the info from the DBV as to denomination that's been inserted, does it?