Hello all - first post on pinside. I have owned my Star Wars for about ten years, but it has been in garage purgatory for the last six of those. I just grew the courage to remove the backbox so that I could get it into the basement and resurrect it. Upon reassembly, I was shocked and oh so happy to see the game start up and play perfectly fine. I ran through diags and aside from a few lamps out everything was working properly.

The next day, my kids were playing and I noticed that I was hearing an electrical hum every time one of the coils fired (not the flippers though). The hum would last a second or so then would go away. We finished that particular game and then turned it off. Later that day, I was going to troubleshoot the problem and turned on the machine only to hear the hum constantly. My mistake was trying to get into the diag menu to "flex" the offending coil, but about 10 seconds in I saw smoking pouring out of the left vertical up kicker so I quickly turned off and unplugged the game.

After researching some similar posts here, I got my DMM out and tested a few things. Turns out the coil has 0 ohms resistance so that is clearly gone and I was able to quickly find the one transistor on the playfield power board that has much less resistance than the others. After referencing my manual, sure enough that transistor, Q3, is for that coil.

Considering I have no pin repair experience, I have a few questions:

1. I see people recommend replacing the pre-driver that sits before the transistor that fried. Is that on the PPB or on the MPU board? What am I looking for?
2. I'm considering replacing the entire PPB with a new one from Rottendog. $80 is worth it to me for piece of mind and to not have to futz with trying to repair this board (I will keep this one as a backup). Amy I crazy for this?
3. There is a small black, square component attached to the coil (see attached photos - not the diode). Is this another transistor? What is it?
4. Is it possible that something that I did when re-connecting the backbox caused this problem considering the game played fine for a day or so before this happened?

Thanks in advance for any assistance and my apologies for the long post.

-Rob

vuk_coil_smoke.jpg vuk_coil_bottom2.jpg

Firebaall,
Had I known the part lingo ahead of time, I totally would have yelled "I'm vuk'ed" when I saw smoke

All, thanks for the awesome replies! I'm still a bit confused as to which transistor is the pre-driver for this circuit. Is that on the PPB?

Also, after replacing the coil and the two transistors, is there a good way to test everything will be fine before firing this back up and melting these things down all over again?

Thanks again - this community is fantastic.

-Rob

Crashdance22, thanks for the response - that helps. I have transistors a new coil on the way so I hope to get working on this soon.

-Rob