I’m troubleshooting my 1980 Stern Galaxy. The last self test tone will not ring and the unit will not finish it’s startup, and as apparently often is the case it was due to a blown F4 fuse on the rectifier board, which is labeled as for coils. It blows immediately when replaced with a new one, suggestive of a short as I understand it. I removed all connectors from the rectifier board except power, and the fuse does not blow. I can replug in all connectors except for the one for the playfield, when I do it blows the F4 fuse.
So my question is what to do to isolate the problem. Ive checked all the coils and they move freely, and there is continuity between the first and three lugs when tested with an ohmmeter. I see no obvious signs of a short due to a wire clearly damaged, etc. What other suggestions are there for finding the problem? Plus, how can I best troubleshoot the rectifier panel to make sure the problem is definitely not there?