After the gumball machine had died, I first checked the fuses and 2 of them were out, one for GI, one for flashers, as written in the manual. After replacement, the gumball now ejects balls (!) but I get two other problems
1. 5 rows are reported short at pinball switch on. In test, yes, all the cells of these rows are lit.
2. All the flashers are on and steady at pinball switch on.
The CPU is good. when I remove the switch matrix connectors, the problem is no longer reported. I checked each connector wire row/column with the ground, no contact.
Wonder how to proceed further. Any help is welcome