Original PC engine not working properly

[16bitgium]

Hi guys,
This weekend I bought a original white PC engine sold as "not tested" for 20 euros. Sadly means not working. I keep getting the yellow screen as if no hucard is inserted. When I wiggle the hucard. I sometimes get a light bluescreen. I have other hardware so I know my hucards work.
After opening up the system it seems that somebody spilled coffee or tea in here. I put it in the dishwasher and now it is very clean. I also cleaned the contacts with PCB cleaner and alcohol to no avail.

 Any protips ?

Can this be a cap problem?