Vending problems

I have an older Pepsi machine (post 60s) with a coinco s75 9800b coin system.  The machine was working fine until the other day.  The machine is set for a nickel. When money is put in, then machine no longer dispenses.  The button at the bottom of the coin box no longer dispenses change when pushed.  Is there any way of fixing this coin machine, or do I need a new coin unit?  Is there any was of bypassing the unit without a free-play switch, in which you can just press a selection and the machine will dispense beverages?  I have read the information on installing a free-play switch, but am unsure of where to put the switch if I need to take this route.  I would appreciate any replies!!  

[johnieG]

Hmm, does it take the nickle? or does it drop it in the coin return cup? if it does reject the coin & the mech won't let you  use the inventory switch (switch that ejects the nickles from the change tubes) then it may have an electrical problem that would mean replacing the mech, repairing it, or as you said bypassing it, as for where to mount a "free-play" switch I've seen this setup used on other machines, pardon the crude drawing, but you get the Idea :'>