Hello everyone, I've been playing my SF2 without issue- the other day I 'matched' after a game, and the knocker didn't go off. It was my first time noticing the issue. I tried to test it, and it wouldn't go. After some digging, I realized the transistor responsible for the knocker on this system 3 machine was missing, like someone removed it and never reinstalled one. I am planning to repair this, but have a few questions.

1) Is there any reason someone wouldn't reinstall the transistor (other than just not wanting to deal with it)?
2) In my mind, I just need to obtain one and solder it back in- would this be accurate? Does anyone else see any other issues?
3) Which transistor would I purchase? I'm having problems finding one searching the numbers on the part.

See pictures below for reference.

Thank you all for your assistance in advance.

2016-12-29 11.08.02 (resized).jpg

2016-12-29 11.11.06 (resized).jpg

2016-12-29 11.08.09 (resized).jpg

I'm pretty sure I found the correct part: http://www.marcospecialties.com/pinball-parts/12N10L

Anyone have insight on the other questions?

I checked the ohms on the coil without a transistor in (not sure if that makes a difference, sorry- still learning on the electrical side). It came to 11.6. I didn't have another similar coil in the game to compare to, but the coil appears to be a Gottlieb A-5195. When I looked up the coil online, it says it should be 11.6ohms, so I'm guessing the coil is fine. That said, I think I'll order the transistor (thanks for the cheaper link!) and go from there.

Thought I'd provide a quick update- got the transistor in the mail today, soldered it in, everything appears to be working as it should now. That knocker is loud!

Also- the infield repair hunch was accurate- I was able to see which transistor was resoldered in to fix a different one that must have gone. I bought a few extras so if I ever need it, i have them without needing to infield repair.

Thank you all again. Happy New Year.