Thought I would provide an update. A couple of weeks ago I desoldered the diode, then transistor. Turns out the transistor was faulty as suspected.
I replaced that and the knocker coil finally works BUT it knocks pathetically. It seems to barely make it up to knock, it sounds more like a tap than a knock. Plus the coil is getting really hot.
My next question is have I got the wrong knocker coil. I replaced the one that was in there with a brand new Gottlieb one of the same type A-1496 but I am now wondering if it's the wrong coil. A check of my Buck Rogers manual and it lists all the coils in the game except... the knocker coil. The Gottlieb manual for that era doesn't list it either. Can anyone tell me what coil should be in a system 1 knocker?
After fixing the knocker (somewhat) I noticed about 4 different switches suddenly not working so next thing will be to track that friggin problem down.
