At the risk of necro posting I want to point out I had the exact same thing happen to me as well. I just acquired a Tri-Zone and after changing batteries the solenoid fuse would blow on startup. I replaced the 2 1/2 amp regular fuse and it popped again. Researched and found it needed a 2 1/2a slo-blow but I only had 2a ones. Put that in and it’s been working fine ever since.

I don’t understand how a board battery swap would make this happen though.

I have to say what a great game. I scored it cheap (By today’s market standards) and had every intention of doing a major playfield retheme as all the targets/switches fit my vision but damned if I didn’t fall in love with the game while I studied the scoring. Set it steep and it plays like a modern title. Great fun out of a surprisingly simple looking game…