I am a novice at this, had pb in the past but never serviced them. I started purchasing again and I really like the techy nature and like learning, however my knowledge is limited, any help is greatly appreciated!

So i purchased this DESW machine, found that the knocker was removed. I am trying to keep the machine original I remember it was so cool getting that thump of a free play when I was a kid! Anyway I purchased a knocker coil from Marco, installed it and went to do a coil test through diagnostics. The diag went through about 6 rounds of testing, the knocker never did activate but noticed lights started flashing wildly on the backbox and then some smoke from the playfield! Immediately shut the machine off, pulled the plug, lifted the playfield. The transformer was super hot, to hot to touch and found that one of the hole coils was also super hot. Not sure if the smoke came from that or the transformer but the knocker was cold. I don't know if this is related to the knocker, or the diagnostics running too long or just coincidence. I have had the game running for a while and never saw any issues so I don't know if the diagnostics, the knocker or just something getting stuck. But it brings up a few questions:
1. Shouldn't the fuse have blown before a coil started to overheat? I checked the fuses when I got the machine and all to specs although 2 of the fuses need new holders installed (another project) but it should not keep it from blowing.
2. Could something like this actually start a fire? Maybe I need to move the machine to the garage or out of the game room!
3. I am wondering if the fact that the knocker was completely removed from the game indicates an issue. Where to start?

Thank you guys in advance!

LTG,
Thank you for the quick reply. I feel a little better about the smoke, I have a fire paranoia- that's probably a good thing! Ill start digging in.