Coinco s75-9800a troubleshooting

[joesquid]

I'm looking for someone knowledgeable about COINCO logic boards.  I've got two S75-9800A units with the same problem.  Apparently they're not issuing a signal to the vend relay.  They both accept coins without a problem but a soda won't vend.  I've tried them both in two separate, working machines to ensure the problem is with the COINCOs.  I'm reading 115VAC to the transformer primary and 18VAC from the secondary.  Even the inventory/payout motor circuit operates correctly but I can't get the vend circuit to operate.  I'm assuming both units' vend coils are good (260 ohms across the coil on each unit) and the price select switches are proven good.  Both CREMs (coin return electromagnet) are good.  All three coin switches are good.  That leaves the logic board and the COINCO manual provides very few details about these boards.  Can anyone assist me troubleshooting these boards?  Apparently at one time COINCO made a logic board tester for these units but I can't find anyone who has one....any help in this area would also be appreciated.
Thanks!!

[MoonDawg]

Interesting note here. These circuit boards have a fusable link that melts in a power surge, although You probably would have seen a burnt spot when you opened the back of the box.
      This promlem has been repaired in the past, by soldering in a 22 guage jumper wire.

[joesquid]

The link is fine.  I've obviously got good pulsating DC or the payout motor wouldn't operate.  The power supply circuitry rectifies the 18VAC to 16-22 VDC.  One output is pulsating DC for the payout motor and the other is straight DC for the logic board.  Beyond that, I'm flying blind because I have no schematic for the logic board itself.  I've drawn up schematics before when none existed but it's very time consuming and I don't feel like re-creating the wheel this time.  Does anyone have a schematic they-re willing to share or have a COINCO logic board tester they're willing to sell?
Thanks!