hey waz it may be the Q19 i think or try reseating cpu connectors 
+1, in particular J4 on the cpu. Could also be J4 on the solenoid driver board having tarnished pins on the board or connector
Q15 on the solenoid driver drives the flipper relay (can be seen in pic in Homepin's post), you could try grounding its metal tab to the aluminium ground shield in the backbox with a test lead, to see if the relay clicks in.
