Coin mech problems?

[russelltatedotcom]

Hi Guys my VMC-56 has just stopped vending (((
I think the problem might lie in the coin mechanism unit
I have power going into the unit (I can here a solenoid clicking when I insert/remove the coin mech plug)
The funny thing is, when the machine is on any inserted coins drop through the mechanism (not activating anything) and drop into the cash box?? When the machine is turned off any inserted coins are rejected via the change slot.
 

Does any body have any idea as to what part is failing and how I might go about fixing it

Thanks for any advice

Russell