Hopper shutting down display

[Magicslots]

I am converting a S2kl with an enhance R-board.  They wanted a coin mech etc on the game.   The coin mech etc, all functions as it should. But when I plug in the hopper,
The game displays a "No Disp" on the leds, and then when the game cycles, it shows nothing and does nothing.  Unplug the hopper and the game runs normally again.  Short in the hopper plug?
 
I have tried 2 different hoppers each give the same problem.  I am stumped here, I have never seen the error before.   Ideas????

[brianfink]

I have never had this problem with a hopper but have had similar problems with a bill exceptor or bad wireing somewhere shorting out and causing the display not to work I also had similar problems just because sombody had plugs in the wrong spot on the back plane so if all your plugs seem to be where they should be then you probly have a short in the plug or wireing for the hopper

[CVslots]

Just had a machine do the same thing....with hopper in, NO DISP showing and no VFD at all. Replaced with known good hopper, problem solved. To verify, we tried the problem hopper in a working machine, and got NO DISP in it as well.

Not exactly sure what the problem with the hopper is, but thought I would post, as many fixes for the NO DISP point towards the bill validator.