What causes a continuous hopper payout on a Williams 400 slot?

[ucanwin]

Continuous hopper payout on a Williams 400 High Speed slot machine.
What would cause this?

[dale]

I had a bad IO board cause this once.

[ucanwin]

A different working I/O board does not make the machine work. No bong, only 110V lighting and bill validator cycle. No digital readouts or lighting on buttons

[ucanwin]

Does anyone else have an idea what I can do to correct the continuous hopper running problem, besides replacing the I/O board?
The I/O board change doesn't seem to get the machine up and running again. All it does, is stop the hopper run problem, but now no bong, no digital readouts, or button lights. Game is dead. Only 110V lighting and bill acceptor cycles on startup. The I/O board now in the machine works fine in another machine.  Desperate for help with this problem.

[dale]

Just checking... Is the IO board that you put in for testing the correct jurisdiction ? 

[ucanwin]

It is the same as was in the machine. NJ
With this I/O board that was in a working machine, now put into the machine with the problem.......only four of the five red LEDs light up. The middle one does not....and the red LED on the far left on the board is now lit. What could be the cause of this?