Well that guide is now bookmarked for sure!
That was very helpful, especially for someone who has never attempted to read an electrical diagram before. It pointed me to the right resistor and transistor, which sure enough, were cooked. Replaced them today, did what amounted to a terrible soldering job (only the 2nd time I've even attempted, the first being connecting the coil!), which my neighbor cleaned up and now my knocker works once more!
The only issue I have now is a number of lamps out that are tied to a certain IC chip that I've already ordered and is on the slow boat from China right now. After that, fingers crossed, everything else I want to deal with is purely on a cosmetic level. That amounts to wanting to change out all the finned posts as they're faded, replace all the drop targets as they are currently a mish mash of various other games, replace all the clear (now yellowed) plastic with new pieces I'm having cut, and put in bulbs for the handful that are burned out. I need to also give the mylar covered playfield a real good cleaning, and then wax it for the first time in probably 15 years, if ever. There is some cracking going on with the mylar, especially around the inserts of the balls, but I don't plan on doing anything about that any time soon.